This article was downloaded by: [University of Sussex Library] On: 01 February 2015, At: 07:05 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
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The Effects of Aerobic Exercise on Psychological Adjustment a
b
Barbara Stetson PhD , David G. Schlundt , Tracy Sbrocco c
d
d
BA , James O. Hill PhD , Teresa Sharp MA & Jamie PopeCordel MS, RD
c
a
Psychology, Illinois Institute of Technology, IL
b
Psychology, Vanderbilt Univeristy
c
Psychology, Vanderbilt University
d
Pediatrics, Vanderbilt University Published online: 26 Oct 2008.
To cite this article: Barbara Stetson PhD , David G. Schlundt , Tracy Sbrocco BA , James O. Hill PhD , Teresa Sharp MA & Jamie Pope-Cordel MS, RD (1993) The Effects of Aerobic Exercise on Psychological Adjustment, Women & Health, 19:4, 1-14, DOI: 10.1300/J013v19n04_01 To link to this article: http://dx.doi.org/10.1300/J013v19n04_01
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The Effects of Aerobic Exercise on Psychological Adjustment: A Randomized Study of Sedentary Obese Women Attempting Weight Loss Barbara Stetson, PhD David G. Schlundt, PhD Tracy Sbrocco, BA James 0. Hill, PhD Teresa Sharp, MA Jamie Pope-Cordel, MS, RD
ABSTRACT. This study evaluated the psychological effects of aerobic conditioning in 40 moderately obese, sedentary women participating in a 12-week behavioral weight loss program. Participants were randomly assigned to a no-exercise or moderate walking condition. Emotional impact of the treatment was assessed in two ways: (1) Subjects reported subjective mood prior to each eating episode and (2) the SCL-90-R was administered before and after the program. Exercisers lost more weight and body fat than non-exercisers. Both groups of subjects showed numerous improvements in mood as a result of participating in the weight loss program. Exercise had no specific differential effect on emotions as measured by daily mood ratings or the SCL-90-R. Exercise did not appear to add appreciably to the psychological benefits of losing weight in this Barbara Stetson is affiliated with the Department of Psychology at the Illinois Institute of Technology. David G. Schlundt and Tracy Sbmcco are affiliated with the Department of Psychology, James 0.Hill and Teresa Sharp are affiliated with the Department of Pediatrics, and Jamie Popecordel is afhlinted with the Department of Psychology at Vanderbilt University. Correspondence concerning this article should be addressed to Barbara Stetson, PhD, Department of Psychology, Life Sciences Building, Illinois Institute of Technology, IIT Center, Chicago, IL 60616. Women & Health, Vol. 19(4) 1992 0 1992 by The Haworth Press, Inc. All rights reserved.
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sedentary obese population. Future studies utilizing longer periods of aerobic exercise training, larger sample size, and exercise specific measures are recommended. The physical and psychological benefits of physical fitness are widely promoted in popular and research literature. Researchers are increasingly recognizing the potential role of exercise in the management of obesity (e.g., Thompson, Jarvie, Lahey & cureton, 1982; Hill, Schlundt, Sbrocco, Sharp, Pope-Cordle, Stetson, Kaler, & Heim, 1989). Many weight control programs routinely include aerobic training to enhance weight loss and weight maintenance. Standard outpatient programs ranging from 8 to 20 weeks have produced greater weight loss with exercise in conjunction with caloric restriction compared to reduced dietary intake alone (Dahlkoetter, Callahan & Linton, 1979; Harris & Hallbauer, 1973: Hill, Schlundt, Sbrocco, Sharp, Pope, Stetson, Kaler, & Heim, 1989). These greater weight losses appear to be maintained at follow-up contacts (Perri, McAdoo, McAllister, Lauer & Yancey, 1986). Programs incorporating moderate exercise have also produced significantly greater reductions in body fat than those employing dietary restriction alone (Hill et al., 1989; Dahlkoetter, 1979). Many clinicians and researchers also tout the psychological benefits of exercise training. A variety of claims have been made regarding the association between aerobic exercise and improved mood, self-concept and stress reduction in persons who are moderately obese (e.g., Stuart, 1975). Participation in a behavioral weight control program per se, appears to result in positive mood changes (Wing, Epstein, Marcus & Kupfer, 1984). Magnitude of weight loss may mediate changes in affect with greater weight losses associated with more substantial decreases in dysphoric mood (see Wing et al., 1984). Initial mood appears to be one of the strongest predictors of mood change following weight management programs, with subjects having the highest anxiety or depression scores showing the greatest improvement (Wing, Marcus, Epstein & Kupfer, 1983). The multifaceted nature of the interventions employed in behavioral weight loss programs makes it difficult to determine which specific components of the treatment are responsible for the observed improvements in mood status.
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The relationship between programmatic exercise and mood change has not been experimentally examined in behavioral weight loss programs with moderately obese individuals. While physical activity continues to be prescribed for stress-reducing effects in obese populations, the vast majority of the research on exercise and mood has been based on nonclinical populations with normal body weight. Unfortunately, many studies of chronic exercise and affective state have compared levels of emotional distress in individuals who are already fit or unfit at the time of mood assessments; without isolating the effects of training by examining changes in psychological function concomitant with changes in fitness (Folkins & S h e , 1981). The few controlled studies of improvements in fitness and impact on psychological variables suggest that increased fitness following physical training is associated with increases in positive affect (Blumenthal, Williams, Needles & Wallace, 1982; Wilson, Morley & Bird, 1980). In a study of persons of normal weight, improvements in physical fitness were associated with concomitant reductions in self-reported anxiety; with fitness-related changes even more pronounced than those obtained by a comparison group trained in cognitive-behavioral stress management (Long, 1985). Greater improvements in self-reported depression have been reported in individuals in exercise programs when compared to nonexercising control groups (Kowal, Patton & Vogal, 1978; McCann & Holmes, 1984). Research suggests that there may be sex differences in the effects of long-term fitness training on physical outcomes with women at lower levels of fitness before and after training compared to men (e.g., Folkins, Lynch, & Gardner, 1992). Sex differences have also been observed in rate of relapse from regular exercise routines (Dubbert, Terre, Rowland, Porzelius & Krug, 1988). In a group of individuals exercising on their own in the community, females were significantly more likely than males to drop out of their regular exercise program (86% versus 63%). Relapse was most likely to occur within the first 3 months, and then again after 1 year of exercise. Degree of change in fitness level following exercise training may mediate changes in psychological variables. An inpatient study of severely obese individuals (150-300 % of ideal body weight) showed that a 6 month program of physical training and hypocaloric re-
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striction (400600 kcal day) resulted in significant improvements physical fitness, substantial weight loss (47.70 kg) and concomitant decreases in Symptom Checklist-90 scores. Few mood changes were indicated in subjects in a diet, no exercise group (Lampman, Schteingart & Foss, 1985). It appears that sex, initial level of fitness, and degree of fitness improvements may all play a role in affective changes following exercise conditioning programs. The present study evaluated the psychological effects of aerobic conditioning in moderately obese, unfit women during a 12-week outpatient weight loss program. Multiple measures of mood state were employed. Subjective mood evaluated on a daily basis using eating diaries, in order to compensate for possible expectancy effects of a pre-posttreatment measure. The SCL-90-R was administered at the start and completion of the training programs. This checklist format has been used in a number of studies examining affect and eating behavior (e.g., Schlundt, Taylor, Hill, Sbrocco, Pope-Cordle, Kasser, & Arnold, 1991; Stetson, 1991). Because the supposed psychological benefits of aerobic exercise have been so well publicized, it is not possible to rule out the hypothesis that changes in subjects self-reports represent an expectancy bias rather than a real change in day-today affective experiences. The Hopkins Symptom checklist revised (SCL-90-R; Derogotis, 1977) was also selected as a self-report measure since it contains subscales tapping a variety of indices of psychological distress and was developed for use with medical populations (The normative sample included a subset of obese women participating in a weight loss program). The experimental design employed random assignment to no exercise and moderate aerobic exercise groups, each in conjunction with dietary restriction.
METHOD Subjects. Forty sedentary, moderately obese women who were 130-160% of ideal body weight, participated in the weight loss program. These participants ranged in age from 21 to 52 (X = 36.6, sd = 7.01). Subjects were recruited via flyers and newspaper advertisements circulated in the general population in Nashville, Tennessee. Subjects who smoked or who had major health
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problems such as diabetes or cardiovascular disease were excluded from the program. A 2 X 2 (diet condition by exercise condition) design was employed in which each subject was randomly assigned to one of the 4 diet and exercise conditions for a period of 12 weeks. Experimental Diets. Subjects who were randomly assigned to the constant diet condition followed a 1200 kcallday diet, based on a food group exchange system. Subjects in the alternating diet condition followed a diet which alternated between 600 and 1800 kcallday in a prescribed pattern. The average caloric intake in the alternating diet over the course of the 12 week program was 1200 kcallday. Alternating and constant diet groups met separately from each other. Sessions were conducted by investigators-with experience in behavioral psychology and nutrition. The behavioral programs were constructed to help subjects identify situations, emotions and behaviors that are associated with inappropriate eating behaviors and to learn and practice more effective strategies for responding to these situations (see Schlundt & Zimering (1988) for a discussion of a skill-training approach to weight loss). Exercise Conditions. Within each diet condition, half of the subjects were randomly assigned to a program of moderate aerobic exercise while the other half were assigned to a no exercise control group. Exercise training consisted of 10 minutes of stretching and warm-up calisthenics followed by brisk walking at a target heart rate of 60-70% of the maximum rate. Training began with 20 minutes of walking during each exercise session in the first week of the program. Aerobic activity was increased over the course of the program. Subjects progressed to 30 minutes of walking per exercise session during weeks 2-4, 40 minutes during weeks 5-7, and finally, to 50 minutes per session during weeks 8-12. Subjects in the exercise condition were required to attend 3 supervised walking sessionslweek held at the Vanderbilt University track during the first 4 weeks of the study. Required number of the supervised sessions was reduced to 2 sessionslweek during weeks 5-8 of the program and 1 supervised sessionlweek during the final 4 weeks of the study. In addition to the supervised exercise sessions, subjects were instructed to exercise on their own in order to meet the goal of 5 bouts of exercise per week. Subjects in the no exercise control - -
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group were instructed to refrain from engaging in regular exercise. The present report focus on the exercise-no exercise conditions collapsed across the 2 diet conditions. Each subject also participated in several physiological tests at the beginning of the study and at completion of the weight loss program. Description and results of the treadmill tests of maximum aerobic capacity, body composition, energy expenditure, and blood pressure are reported elsewhere (Hill, Schlundt, Sbrocco, Sharp, Pope, Stetson, Kaler, & Heim, 1989). Self Monitoring of Dietary Intake. Subjects kept baseline selfmonitoring diaries for 2 weeks prior to entry into the study. Dietary intake was continuously monitored throughout the program, with type and amount of each food recorded and coded according to food groups by each subject. Subjects employed the American Diabetes Association food exchange system (ADA, 1987) recording the number of servings from each of the five food groups (meats, milks, vegetables, starches, and fruits) consumed at each meal. Subjects were given a 28-page coding manual which listed commonly eaten foods and the number of exchanges from each food group for a specific serving size. Self-Report of Emotions and Mood State. Subjects indicated emotional, physical and cognitive antecedents to each eating episode on a checklist in the food diary. Negative emotional antecedents to eating behavior included feeling depressed, worried, irritable, nervous, afraid, stressed, bored and angry. Positive emotions included feeling excited, challenged and happy. Physical symptoms preceding eating episodes included feeling weak, tired and in pain. All subjects also completed a self-report inventory of emotional distress, the SCL-90-R (Derogotis, 1977) at baseline and posttreatment.
RESULTS Adherence to Diet and Exercise Sessions Eight of the original 40 subjects did not complete the program, yielding a 20% drop out rate. Three additional participants did not complete all follow-up questionnaires. Eighteen exercisers and 11 non exercisers completed all measures.
Self-reports recorded on the back of the food diary indicated that subjects in the exercise conditions engaged in an average of more than 5 walking sessionslweek. An average of 95% of the self-monitoring food diaries were completed and turned in to the investigators for the 32 subjects completing the intervention programs.
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Relevant Physiological Outcomes Overall, exercisers lost more weight than sedentary dieters. (8.6+1-.9 versus 6.3 +I-.9 kg; p < .05; see Hill et al., 1989). Exercisers had a greater reduction in body fat (43.0+1- 1.1% to 38.5+1-1.3%) than did sedentary dieters (from 43.8 +I-1.1% to 41.1+/-1.1%; p < .05). For exercisers, 86% of the weight loss came from fat, while for non-exercisers, 73% of weight loss came from fat. Weight loss alone led to improved V0,Max. In all subjects (from 23.7+1- .73 to 28.2+1- 1.2 mllkglminute, p < .05). Although exercise subjects tended to show a greater increase in V0,Max with training, changes were idiosyncratic within subjects &id not statistically significant between groups (from X = 24.37+/- 1.2 to 29.58+/- 1.8 mllkglminute).
Exercke and Mood Ratings
Diary data and SCL-90-R subscales were analyzed using an univariate analysis of covariance with exercise as a between subjects factor. The covariate was weight loss, since degree of weight loss might have an independent effect on changes in affect. There was a main effect for exercise on the Interpersonal Sensitivity subscale of the SCL-90-R @ < .05). None of the other SCL-90-R scales showed an effect for exercise. Following participation in the weight management programs, subjects showed significant reductions in the SCL-90-R subscales measuring: Somatization (p < .01), ObsessionlCompulsion (p < .01), Interpersonal Sensitivity @ < .001), Depression @ < .05), Paranoia (p < .05) and the Global Symptom Index (p < .01). There were no changes in Hostility, Anxiety, Phobic Anxiety or Psychoticism subscales. There were no significant effects for the weight-loss covariate on any of the SCL-90 scales indicating that
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the same results would have been obtained had we not controlled for weight loss. For purposes of analysis, the mood adjectives recorded on the eating diaries were combined to form three scales: negative mood (depressed, worried, irritable, nervous, afraid, stressed, bored and angry), positive mood (excited, challenged and happy), and physical symptoms (weak, tired and in pain). These scores reflect the average number of affective adjectives falling into each of the 3 categories checked on each diary entry either during baseline or treatment. Subjects significantly decreased the number of negative mood @ < 0.0001) and physical symptoms @ < 0.001) adjectives checked at eating episodes during treatment with no change in the rate of checking positive adjectives @ < 0.35). The specific effects of exercise were clearly absent for positive emotions @ < 0.59) and physical symptoms @ < 0.66). The main effect of exercise on negative emotions favored greater reductions in checking negative mood items for the exercise subjects but did not reach conventional levels of significance @ < 0.073). Table 1 presents the means and standard deviations of the dependent variables for the exercise and no-exercise groups.
DISCUSSION Using a randomized design, this study failed to find strong evidence for the independent benefit of exercise in the reduction of depression, anxiety, or other negative affective states. Participation in the 12-week exercise program resulted in beneficial physiological outcomes. Exercising subjects lost significantly more weight and had greater reductions in percent body fat than did non-exercisers. These physical benefits occurred even though the exercise program was of moderate duration and intensity. A walking program appears to be an easily accessible, safe and appropriate intensity level for obese, and initially unfit participants. The only SCL-90-R subscale showing a significant decrease from baseline to follow-up for exercisers was the Interpersonal Sensitivity Subscale. One potential interpretation of this change is that exercisers became less self-conscious and had improvements in body image.
Stetson et al. .-.
Table 1. Standardized Means and Standard Deviations on the SCL-PO-R and Diary Measures Exercise ,
Baseline Mean S.O.
Measure
'
No Exercise
Post Mean S.D.
Easel ine Mean S.D.
Post Mean S.D.
-35 .42 .54
.52 .44
.37 .42 .51
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SCL-SO-R
Somatiz Obsess InPerSen Oepress Anxiety Hostile Phobic A n x Paranoid Psychotic GSI
.13 .28 .23 .45 .53 .72 .41 .67 .17 .23 .24 .40 .OO .OO .ll .17 .10 .22 .23 .31
Diary
.69 .50 .82
Neg Moods Pos Moods Phys Sym
.37 .32 .28
.14 .31 .23
.72
.33 .21 .42
.27 .30 .42
' +
-----------------------------------------------------
' SCL-90-R was administered pre and posttreatment while the diary measures reflect affect during the 12 week treatment period.
.. Significant ' I
reductions in exercise group
Significant reductions following participation in weight 'management program
When the emotional impact of exercise evaluated by examining the mood checklist completed at each eating episode during baseline and treatment, there was a trend for reduced level of negative affect. This pattern of findings may suggest that daily measures of mood may have been more sensitive than the SCL-90-R. While no improvements in emotional distress (e.g., depression, anxiety) were specifically associated with exercise training, participation in the weight loss program proved psychologically beneficial, even after controlling for the effects of weight loss, with
..
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consistent reduction across SCL-90-R scores and reduction of levels of negative affect on diary measures. The finding of reductions may reflect a decrease in eating in response to negative emotions and physical symptoms on diary measures. Emotional eating was addressed as part of the skill-training interaction package. The 12-week weight management sessions were conducted in discussion-oriented group format, which may have fostered a supportive environment that participants found beneficial. In addition, specific sessions were devoted to finding alternative strategies for dealing with negative emotions which subjects may have successfully employed. Some of the findings, such as reduced interpersonal sensitivity on the SCL-90-R, may have been a direct consequence of increased self-confidence that occurred as a result of losing weight and improving appearance. The small sample size in follow-up analysis resulted in relatively low levels of statistical power to detect diet and exercise interactions. However, power was sufficient to detect changes in interpersonal sensitivity subscale scores and diary measures for exercising subjects. Follow-up research utilizing a larger sample would add to the strength of the present pattern of findings. The pattern of findings in this study raises several issues that must be considered when evaluating the psychological outcomes of exercise training in moderately obese populations. Subjects' initial SCL-90-R scores were relatively low, and absence of exerciserelated mood changes may reflect a floor effect. These subjects were clearly not exhibiting clinically significant psychological distress. It may be that subjects with clinically significant levels of emotional distress might benefit more specifically from an exercise intervention. Initial fitness levels were very low in the women who participated in the present study. Although intervention resulted in significant improvements in aerobic capacity, improvement may have been insufficient to have a significant effect on psychological mood. The exercise-related mood improvements discussed in other studies (e.g., Folkins & Sime, 1981; Lampman et al., 1985) were observed in nonobese persons with relatively high levels of fitness and in severely obese persons who had dramatic increases in fitness as a result of long-term, intensive exercise intervention. It is note-
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worthy, however, that the type and intensity of exercise used in this study was sufficient to result in differential weight loss and body composition changes. In addition, the type of moderate intensity, out-patient walking program used in this study may be the most realistic form of exercise for sedentary, obese women. Self-perceptions of competence regarding fitness and physical abilities have been linked to improved mood and self-concept as well as adherence to exercise programs (She, 1984). While dietary restriction and attempts at weight loss are familiar to many weight loss program participants, most lack any previous aerobic training experience (Brownell, Stunkard & Albaum, 1980). Further, despite physical improvements, increased confidence in exercise abilities and habitual exercise behaviors in obese dieters may require a longer training period than the standard 12-week diet and exercise program provides. Despite substantial gains in fitness, such as reduced weight and body fat, exercisers' changes in oxygen uptake were idiosyncratic and not statistically significant overall (see Hill et al., 1989). It is possible that additional physical and psychological changes might have occurred with longer or more intense training. Additional studies incorporating more long-term aerobic training programs in initially unfit subjects seem warranted. The psychological benefits of more long-term exercise programs for obese dieters is as yet unclear. The difficulty with maintaining continuous and positive exercise behavior over the long term is evidenced by high dropout rates within the first 3 months of training among nonobese, regular exercisers, particularly women. More discouraging is that overweight persons are even less likely to continue a fitness program (Dishman & Ickes, 1981; Brownell & Stunkard, 1980). However, self-reported exercise adherence was high among subjects who participated in the present study's exercise groups, at least during the 3-months of treatment. Notably, ninety percent of exercisers completed the program compared to fifty-five percent of nonexercising subjects. Exercising subjects may have found this particular aspect of the program enjoyable, enhancing their participation in the program as a whole. It is possible that the additional contact with project staff and group members available during initial walking sessions at the track increased subjects involvement and commitment to the program, promoting greater
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long-term program adherence. The utility of periodic booster sessions with novice exercisers may be an important area for exploration in exercise adherence studies conducted with sedentary women. This study differed from most evaluations of the psychological benefits of exercise by employing two very different outcome measures; self-repon questionnaires and daily measures of mood included in eating diaries. Comparison of other prospective measures of affect and exercise related cognitions may yield further information on the process of fitness training. King, Taylor, Haskell and DeBusk (1989) measured multiple psychological variables on individualized-type rating scales in a study of healthy middle aged adults who were randomized to exercising in non-exercising conditions. Only items most closely related to actual physical changes associated with exercise showed improvement. The present study replicates the findings of Wing et al. (1984) that participation in a behavioral weight control program produces beneficial psychological changes. However, we did not replicate the finding that degree of weight loss was associated with the amount of psychological benefit. More evidence is needed before exercise can be recommended as a specific anxiolytic therapy for sedentary obese. Exercise clearly has physical benefits for obese women wishing to lose weight. However, claims that aerobic exercise will also lead to reductions in anxiety, depression, or other negative affects in obese women who are not physically conditioned are not supported by these data. REFERENCES American Diabetes Association, (1987). Nutritional recommendations and principals for individuals with diabetes mcllitus: 1986. Diabetes Care, 10, 126-132. Blumenthal, J.A., W m s , S., Needel, T.L. & Wallace, A.G. (1982). Psychological and physiological effects of physical condition on the elderly. Journal of P~chosomnricResearch, 26, 505-510. Brownell, K.D. & Stunkard, A.J. (1980). Physical activity in the development and control of obesity. In A.J. Stunkani (Ed.) Obesiry. Philadelphia, PA: W.B. Saunders & Co. Brownell, K.D., Stunkard, A.J. & Albaum, J.M. (1980). Evaluation and modification of exercise palterns in the natural environment. American Journol of Psychiahy, 137, 1540-1545.
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Dahlkoetter, I., Callahan. E.J. & Linton, J. (1979). Obesity and the unbalanced energy equation: exercise versus eating habit change. Journal of Consulting and Clinical Psychology, 47, 5, 898-905. Derogotis, L.R. (197'7). The SCL-90-R: Administration, s w M g and procedures. Manual-I. Baltimore: Clinical Psychometrics Research. Dishman, R.K. & Ickes, W. (1981). Self-motivation and adherence to therapeutic exercise. Journal of Behavioral Medicine, 4, 421438. Dubbert, P.M, Tern, L., Rowland, A.K., Ponetius, J.E. &Krug, L.M. (1988). Relapse in Exercise. Presentation, Society of Behavioral Medicine Annual Convention, April, Boston MA. Folkins, C.H.,Lynch, S. & Gardner, M.M. (1972). Psychological fimess as a function of physical fitness. Archives of Physical Medicine and RehabiIitarion, 53, 503-508. Folkins, C.H. & S h e , W.R. (1981). Physical fitness training and mental health. American Psychologirl, 36, 4, 373-389. Harris, M.B., & Hallbauer, E.S. (1973). Selfdirected weight control through eating and exercise. Behavior Research and nterapy, 11, 523-529. Hill, 1.0.. Schlundt, D.G., Sbrocw, T., Sharp, Teresa, Pope, I.. Stetson. B., Kaler, M. & Heim, C. (1989). Food restriction in obese women: effects of alternating low and moderate caloric intake. Journal of Clinical Nufririon, 50, 2, 248-254. King, A.C., Taylor, C.B., Haskell, W.L.& DeBusk, R.F. (1989). Influence of regular aerobic exercise on psychological health: A randomized, controlled trial of healthy middle aged adults. Kowal, D., Patton, J. & Vogal, J. (1978). Psychological states and aerobic fitness of male and female recruits before and after basic training. Aviation, Space, and Environmental Medicine, 49, 603-606. Lampman, R.M., Schteingart, D.E.& Foss, M.L. (1985). Exercise as a p M therapy for the extremely obese. Medicine and Science in Sports and Grercise, 18, 1. 19-24. Long, B. (1985). Aerobic conditioning and stress inoculation: A comparison of stress-management interventions. Cognitive lherapy and Research, 8, 517542. McCann, I.L. & Holmes, D.S. (1984). Influence of aerobic exercise on dcpression. Journal of Perso~Iityand Social Psychology, 46, 1142-1147. Pem. M.G., McAdoo, W.G., McAlhter, D.A., Lauer, J.B. & Yancey, D.Z. (1986). Enhancing the efficacy of behavior therapy for obesity: Effects of aerobic exercise and a multicomponent maintenance program. Journal of Consulting and Clinical Psychology, 54, 5, 670-675. Schlundt, D.G.. Taylor, D., Hill, J.O., Sbrocco, T., PopaCordle. J., Kasser, T. & Arnold D. (1991). Taxonomy of obese female participants in a weight loss program. American Journal of Clinical Nutrition, 53, 1151-8. Schlundt, D.G., & Z i e M g . R.T., (1988). The dieter's inventory of eating temptations: A measure of weight control wmpetence. Addictive Behaviors, 13, 151-164.
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S h e , W.E. (1984). Rychological benefits of exercise. Advances, 1, 4, 15-29. Soenstroem, R.J. (1984). Exercise and self-esteem. Exercise and Spon Sciences Reviews, 12, 123-155. Stason, B.A. (1991). Development ond evaluation of aprobkm solving and behovioral skills troining program to promote adherence to the lDDM dietary regimen. Doctoral Thesis, Vanderbit University. Stuatt, R.B. (1975). Exercise prescription in weight management: Advantages, bhniques and obstacles. Obesiry/Boriotric Medicine, 4, 16-24. Thompson. I.K., Jarvie, G.J.,Lahey, B.B. & Curetan, K.J. (1982). Exercise and obesity: Etiology, physiology, and intervention. Psychological Bulletin, 91, 1, 55-79.
Vasterling, 1.1. (1988). Aerobic jhess, acute exercbe, and coping with stress. Unpublished Doctoral Dissertation, Vanderbiit University, Nashville, Tennessee. Wdson, V.E., Morley, N.C., & Bird,E.I. (1980). Mood profiles of marathon runners, joggers, and nonexercisers. Perceptual ond Motor SkiUs, 50, 117118.
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The Effects of Aerobic Exercise on Psychological Adjustment a
b
Barbara Stetson PhD , David G. Schlundt , Tracy Sbrocco c
d
d
BA , James O. Hill PhD , Teresa Sharp MA & Jamie PopeCordel MS, RD
c
a
Psychology, Illinois Institute of Technology, IL
b
Psychology, Vanderbilt Univeristy
c
Psychology, Vanderbilt University
d
Pediatrics, Vanderbilt University Published online: 26 Oct 2008.
To cite this article: Barbara Stetson PhD , David G. Schlundt , Tracy Sbrocco BA , James O. Hill PhD , Teresa Sharp MA & Jamie Pope-Cordel MS, RD (1993) The Effects of Aerobic Exercise on Psychological Adjustment, Women & Health, 19:4, 1-14, DOI: 10.1300/J013v19n04_01 To link to this article: http://dx.doi.org/10.1300/J013v19n04_01
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The Effects of Aerobic Exercise on Psychological Adjustment: A Randomized Study of Sedentary Obese Women Attempting Weight Loss Barbara Stetson, PhD David G. Schlundt, PhD Tracy Sbrocco, BA James 0. Hill, PhD Teresa Sharp, MA Jamie Pope-Cordel, MS, RD
ABSTRACT. This study evaluated the psychological effects of aerobic conditioning in 40 moderately obese, sedentary women participating in a 12-week behavioral weight loss program. Participants were randomly assigned to a no-exercise or moderate walking condition. Emotional impact of the treatment was assessed in two ways: (1) Subjects reported subjective mood prior to each eating episode and (2) the SCL-90-R was administered before and after the program. Exercisers lost more weight and body fat than non-exercisers. Both groups of subjects showed numerous improvements in mood as a result of participating in the weight loss program. Exercise had no specific differential effect on emotions as measured by daily mood ratings or the SCL-90-R. Exercise did not appear to add appreciably to the psychological benefits of losing weight in this Barbara Stetson is affiliated with the Department of Psychology at the Illinois Institute of Technology. David G. Schlundt and Tracy Sbmcco are affiliated with the Department of Psychology, James 0.Hill and Teresa Sharp are affiliated with the Department of Pediatrics, and Jamie Popecordel is afhlinted with the Department of Psychology at Vanderbilt University. Correspondence concerning this article should be addressed to Barbara Stetson, PhD, Department of Psychology, Life Sciences Building, Illinois Institute of Technology, IIT Center, Chicago, IL 60616. Women & Health, Vol. 19(4) 1992 0 1992 by The Haworth Press, Inc. All rights reserved.
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sedentary obese population. Future studies utilizing longer periods of aerobic exercise training, larger sample size, and exercise specific measures are recommended. The physical and psychological benefits of physical fitness are widely promoted in popular and research literature. Researchers are increasingly recognizing the potential role of exercise in the management of obesity (e.g., Thompson, Jarvie, Lahey & cureton, 1982; Hill, Schlundt, Sbrocco, Sharp, Pope-Cordle, Stetson, Kaler, & Heim, 1989). Many weight control programs routinely include aerobic training to enhance weight loss and weight maintenance. Standard outpatient programs ranging from 8 to 20 weeks have produced greater weight loss with exercise in conjunction with caloric restriction compared to reduced dietary intake alone (Dahlkoetter, Callahan & Linton, 1979; Harris & Hallbauer, 1973: Hill, Schlundt, Sbrocco, Sharp, Pope, Stetson, Kaler, & Heim, 1989). These greater weight losses appear to be maintained at follow-up contacts (Perri, McAdoo, McAllister, Lauer & Yancey, 1986). Programs incorporating moderate exercise have also produced significantly greater reductions in body fat than those employing dietary restriction alone (Hill et al., 1989; Dahlkoetter, 1979). Many clinicians and researchers also tout the psychological benefits of exercise training. A variety of claims have been made regarding the association between aerobic exercise and improved mood, self-concept and stress reduction in persons who are moderately obese (e.g., Stuart, 1975). Participation in a behavioral weight control program per se, appears to result in positive mood changes (Wing, Epstein, Marcus & Kupfer, 1984). Magnitude of weight loss may mediate changes in affect with greater weight losses associated with more substantial decreases in dysphoric mood (see Wing et al., 1984). Initial mood appears to be one of the strongest predictors of mood change following weight management programs, with subjects having the highest anxiety or depression scores showing the greatest improvement (Wing, Marcus, Epstein & Kupfer, 1983). The multifaceted nature of the interventions employed in behavioral weight loss programs makes it difficult to determine which specific components of the treatment are responsible for the observed improvements in mood status.
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Sretson er al.
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The relationship between programmatic exercise and mood change has not been experimentally examined in behavioral weight loss programs with moderately obese individuals. While physical activity continues to be prescribed for stress-reducing effects in obese populations, the vast majority of the research on exercise and mood has been based on nonclinical populations with normal body weight. Unfortunately, many studies of chronic exercise and affective state have compared levels of emotional distress in individuals who are already fit or unfit at the time of mood assessments; without isolating the effects of training by examining changes in psychological function concomitant with changes in fitness (Folkins & S h e , 1981). The few controlled studies of improvements in fitness and impact on psychological variables suggest that increased fitness following physical training is associated with increases in positive affect (Blumenthal, Williams, Needles & Wallace, 1982; Wilson, Morley & Bird, 1980). In a study of persons of normal weight, improvements in physical fitness were associated with concomitant reductions in self-reported anxiety; with fitness-related changes even more pronounced than those obtained by a comparison group trained in cognitive-behavioral stress management (Long, 1985). Greater improvements in self-reported depression have been reported in individuals in exercise programs when compared to nonexercising control groups (Kowal, Patton & Vogal, 1978; McCann & Holmes, 1984). Research suggests that there may be sex differences in the effects of long-term fitness training on physical outcomes with women at lower levels of fitness before and after training compared to men (e.g., Folkins, Lynch, & Gardner, 1992). Sex differences have also been observed in rate of relapse from regular exercise routines (Dubbert, Terre, Rowland, Porzelius & Krug, 1988). In a group of individuals exercising on their own in the community, females were significantly more likely than males to drop out of their regular exercise program (86% versus 63%). Relapse was most likely to occur within the first 3 months, and then again after 1 year of exercise. Degree of change in fitness level following exercise training may mediate changes in psychological variables. An inpatient study of severely obese individuals (150-300 % of ideal body weight) showed that a 6 month program of physical training and hypocaloric re-
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striction (400600 kcal day) resulted in significant improvements physical fitness, substantial weight loss (47.70 kg) and concomitant decreases in Symptom Checklist-90 scores. Few mood changes were indicated in subjects in a diet, no exercise group (Lampman, Schteingart & Foss, 1985). It appears that sex, initial level of fitness, and degree of fitness improvements may all play a role in affective changes following exercise conditioning programs. The present study evaluated the psychological effects of aerobic conditioning in moderately obese, unfit women during a 12-week outpatient weight loss program. Multiple measures of mood state were employed. Subjective mood evaluated on a daily basis using eating diaries, in order to compensate for possible expectancy effects of a pre-posttreatment measure. The SCL-90-R was administered at the start and completion of the training programs. This checklist format has been used in a number of studies examining affect and eating behavior (e.g., Schlundt, Taylor, Hill, Sbrocco, Pope-Cordle, Kasser, & Arnold, 1991; Stetson, 1991). Because the supposed psychological benefits of aerobic exercise have been so well publicized, it is not possible to rule out the hypothesis that changes in subjects self-reports represent an expectancy bias rather than a real change in day-today affective experiences. The Hopkins Symptom checklist revised (SCL-90-R; Derogotis, 1977) was also selected as a self-report measure since it contains subscales tapping a variety of indices of psychological distress and was developed for use with medical populations (The normative sample included a subset of obese women participating in a weight loss program). The experimental design employed random assignment to no exercise and moderate aerobic exercise groups, each in conjunction with dietary restriction.
METHOD Subjects. Forty sedentary, moderately obese women who were 130-160% of ideal body weight, participated in the weight loss program. These participants ranged in age from 21 to 52 (X = 36.6, sd = 7.01). Subjects were recruited via flyers and newspaper advertisements circulated in the general population in Nashville, Tennessee. Subjects who smoked or who had major health
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problems such as diabetes or cardiovascular disease were excluded from the program. A 2 X 2 (diet condition by exercise condition) design was employed in which each subject was randomly assigned to one of the 4 diet and exercise conditions for a period of 12 weeks. Experimental Diets. Subjects who were randomly assigned to the constant diet condition followed a 1200 kcallday diet, based on a food group exchange system. Subjects in the alternating diet condition followed a diet which alternated between 600 and 1800 kcallday in a prescribed pattern. The average caloric intake in the alternating diet over the course of the 12 week program was 1200 kcallday. Alternating and constant diet groups met separately from each other. Sessions were conducted by investigators-with experience in behavioral psychology and nutrition. The behavioral programs were constructed to help subjects identify situations, emotions and behaviors that are associated with inappropriate eating behaviors and to learn and practice more effective strategies for responding to these situations (see Schlundt & Zimering (1988) for a discussion of a skill-training approach to weight loss). Exercise Conditions. Within each diet condition, half of the subjects were randomly assigned to a program of moderate aerobic exercise while the other half were assigned to a no exercise control group. Exercise training consisted of 10 minutes of stretching and warm-up calisthenics followed by brisk walking at a target heart rate of 60-70% of the maximum rate. Training began with 20 minutes of walking during each exercise session in the first week of the program. Aerobic activity was increased over the course of the program. Subjects progressed to 30 minutes of walking per exercise session during weeks 2-4, 40 minutes during weeks 5-7, and finally, to 50 minutes per session during weeks 8-12. Subjects in the exercise condition were required to attend 3 supervised walking sessionslweek held at the Vanderbilt University track during the first 4 weeks of the study. Required number of the supervised sessions was reduced to 2 sessionslweek during weeks 5-8 of the program and 1 supervised sessionlweek during the final 4 weeks of the study. In addition to the supervised exercise sessions, subjects were instructed to exercise on their own in order to meet the goal of 5 bouts of exercise per week. Subjects in the no exercise control - -
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group were instructed to refrain from engaging in regular exercise. The present report focus on the exercise-no exercise conditions collapsed across the 2 diet conditions. Each subject also participated in several physiological tests at the beginning of the study and at completion of the weight loss program. Description and results of the treadmill tests of maximum aerobic capacity, body composition, energy expenditure, and blood pressure are reported elsewhere (Hill, Schlundt, Sbrocco, Sharp, Pope, Stetson, Kaler, & Heim, 1989). Self Monitoring of Dietary Intake. Subjects kept baseline selfmonitoring diaries for 2 weeks prior to entry into the study. Dietary intake was continuously monitored throughout the program, with type and amount of each food recorded and coded according to food groups by each subject. Subjects employed the American Diabetes Association food exchange system (ADA, 1987) recording the number of servings from each of the five food groups (meats, milks, vegetables, starches, and fruits) consumed at each meal. Subjects were given a 28-page coding manual which listed commonly eaten foods and the number of exchanges from each food group for a specific serving size. Self-Report of Emotions and Mood State. Subjects indicated emotional, physical and cognitive antecedents to each eating episode on a checklist in the food diary. Negative emotional antecedents to eating behavior included feeling depressed, worried, irritable, nervous, afraid, stressed, bored and angry. Positive emotions included feeling excited, challenged and happy. Physical symptoms preceding eating episodes included feeling weak, tired and in pain. All subjects also completed a self-report inventory of emotional distress, the SCL-90-R (Derogotis, 1977) at baseline and posttreatment.
RESULTS Adherence to Diet and Exercise Sessions Eight of the original 40 subjects did not complete the program, yielding a 20% drop out rate. Three additional participants did not complete all follow-up questionnaires. Eighteen exercisers and 11 non exercisers completed all measures.
Self-reports recorded on the back of the food diary indicated that subjects in the exercise conditions engaged in an average of more than 5 walking sessionslweek. An average of 95% of the self-monitoring food diaries were completed and turned in to the investigators for the 32 subjects completing the intervention programs.
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Relevant Physiological Outcomes Overall, exercisers lost more weight than sedentary dieters. (8.6+1-.9 versus 6.3 +I-.9 kg; p < .05; see Hill et al., 1989). Exercisers had a greater reduction in body fat (43.0+1- 1.1% to 38.5+1-1.3%) than did sedentary dieters (from 43.8 +I-1.1% to 41.1+/-1.1%; p < .05). For exercisers, 86% of the weight loss came from fat, while for non-exercisers, 73% of weight loss came from fat. Weight loss alone led to improved V0,Max. In all subjects (from 23.7+1- .73 to 28.2+1- 1.2 mllkglminute, p < .05). Although exercise subjects tended to show a greater increase in V0,Max with training, changes were idiosyncratic within subjects &id not statistically significant between groups (from X = 24.37+/- 1.2 to 29.58+/- 1.8 mllkglminute).
Exercke and Mood Ratings
Diary data and SCL-90-R subscales were analyzed using an univariate analysis of covariance with exercise as a between subjects factor. The covariate was weight loss, since degree of weight loss might have an independent effect on changes in affect. There was a main effect for exercise on the Interpersonal Sensitivity subscale of the SCL-90-R @ < .05). None of the other SCL-90-R scales showed an effect for exercise. Following participation in the weight management programs, subjects showed significant reductions in the SCL-90-R subscales measuring: Somatization (p < .01), ObsessionlCompulsion (p < .01), Interpersonal Sensitivity @ < .001), Depression @ < .05), Paranoia (p < .05) and the Global Symptom Index (p < .01). There were no changes in Hostility, Anxiety, Phobic Anxiety or Psychoticism subscales. There were no significant effects for the weight-loss covariate on any of the SCL-90 scales indicating that
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the same results would have been obtained had we not controlled for weight loss. For purposes of analysis, the mood adjectives recorded on the eating diaries were combined to form three scales: negative mood (depressed, worried, irritable, nervous, afraid, stressed, bored and angry), positive mood (excited, challenged and happy), and physical symptoms (weak, tired and in pain). These scores reflect the average number of affective adjectives falling into each of the 3 categories checked on each diary entry either during baseline or treatment. Subjects significantly decreased the number of negative mood @ < 0.0001) and physical symptoms @ < 0.001) adjectives checked at eating episodes during treatment with no change in the rate of checking positive adjectives @ < 0.35). The specific effects of exercise were clearly absent for positive emotions @ < 0.59) and physical symptoms @ < 0.66). The main effect of exercise on negative emotions favored greater reductions in checking negative mood items for the exercise subjects but did not reach conventional levels of significance @ < 0.073). Table 1 presents the means and standard deviations of the dependent variables for the exercise and no-exercise groups.
DISCUSSION Using a randomized design, this study failed to find strong evidence for the independent benefit of exercise in the reduction of depression, anxiety, or other negative affective states. Participation in the 12-week exercise program resulted in beneficial physiological outcomes. Exercising subjects lost significantly more weight and had greater reductions in percent body fat than did non-exercisers. These physical benefits occurred even though the exercise program was of moderate duration and intensity. A walking program appears to be an easily accessible, safe and appropriate intensity level for obese, and initially unfit participants. The only SCL-90-R subscale showing a significant decrease from baseline to follow-up for exercisers was the Interpersonal Sensitivity Subscale. One potential interpretation of this change is that exercisers became less self-conscious and had improvements in body image.
Stetson et al. .-.
Table 1. Standardized Means and Standard Deviations on the SCL-PO-R and Diary Measures Exercise ,
Baseline Mean S.O.
Measure
'
No Exercise
Post Mean S.D.
Easel ine Mean S.D.
Post Mean S.D.
-35 .42 .54
.52 .44
.37 .42 .51
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SCL-SO-R
Somatiz Obsess InPerSen Oepress Anxiety Hostile Phobic A n x Paranoid Psychotic GSI
.13 .28 .23 .45 .53 .72 .41 .67 .17 .23 .24 .40 .OO .OO .ll .17 .10 .22 .23 .31
Diary
.69 .50 .82
Neg Moods Pos Moods Phys Sym
.37 .32 .28
.14 .31 .23
.72
.33 .21 .42
.27 .30 .42
' +
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' SCL-90-R was administered pre and posttreatment while the diary measures reflect affect during the 12 week treatment period.
.. Significant ' I
reductions in exercise group
Significant reductions following participation in weight 'management program
When the emotional impact of exercise evaluated by examining the mood checklist completed at each eating episode during baseline and treatment, there was a trend for reduced level of negative affect. This pattern of findings may suggest that daily measures of mood may have been more sensitive than the SCL-90-R. While no improvements in emotional distress (e.g., depression, anxiety) were specifically associated with exercise training, participation in the weight loss program proved psychologically beneficial, even after controlling for the effects of weight loss, with
..
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consistent reduction across SCL-90-R scores and reduction of levels of negative affect on diary measures. The finding of reductions may reflect a decrease in eating in response to negative emotions and physical symptoms on diary measures. Emotional eating was addressed as part of the skill-training interaction package. The 12-week weight management sessions were conducted in discussion-oriented group format, which may have fostered a supportive environment that participants found beneficial. In addition, specific sessions were devoted to finding alternative strategies for dealing with negative emotions which subjects may have successfully employed. Some of the findings, such as reduced interpersonal sensitivity on the SCL-90-R, may have been a direct consequence of increased self-confidence that occurred as a result of losing weight and improving appearance. The small sample size in follow-up analysis resulted in relatively low levels of statistical power to detect diet and exercise interactions. However, power was sufficient to detect changes in interpersonal sensitivity subscale scores and diary measures for exercising subjects. Follow-up research utilizing a larger sample would add to the strength of the present pattern of findings. The pattern of findings in this study raises several issues that must be considered when evaluating the psychological outcomes of exercise training in moderately obese populations. Subjects' initial SCL-90-R scores were relatively low, and absence of exerciserelated mood changes may reflect a floor effect. These subjects were clearly not exhibiting clinically significant psychological distress. It may be that subjects with clinically significant levels of emotional distress might benefit more specifically from an exercise intervention. Initial fitness levels were very low in the women who participated in the present study. Although intervention resulted in significant improvements in aerobic capacity, improvement may have been insufficient to have a significant effect on psychological mood. The exercise-related mood improvements discussed in other studies (e.g., Folkins & Sime, 1981; Lampman et al., 1985) were observed in nonobese persons with relatively high levels of fitness and in severely obese persons who had dramatic increases in fitness as a result of long-term, intensive exercise intervention. It is note-
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worthy, however, that the type and intensity of exercise used in this study was sufficient to result in differential weight loss and body composition changes. In addition, the type of moderate intensity, out-patient walking program used in this study may be the most realistic form of exercise for sedentary, obese women. Self-perceptions of competence regarding fitness and physical abilities have been linked to improved mood and self-concept as well as adherence to exercise programs (She, 1984). While dietary restriction and attempts at weight loss are familiar to many weight loss program participants, most lack any previous aerobic training experience (Brownell, Stunkard & Albaum, 1980). Further, despite physical improvements, increased confidence in exercise abilities and habitual exercise behaviors in obese dieters may require a longer training period than the standard 12-week diet and exercise program provides. Despite substantial gains in fitness, such as reduced weight and body fat, exercisers' changes in oxygen uptake were idiosyncratic and not statistically significant overall (see Hill et al., 1989). It is possible that additional physical and psychological changes might have occurred with longer or more intense training. Additional studies incorporating more long-term aerobic training programs in initially unfit subjects seem warranted. The psychological benefits of more long-term exercise programs for obese dieters is as yet unclear. The difficulty with maintaining continuous and positive exercise behavior over the long term is evidenced by high dropout rates within the first 3 months of training among nonobese, regular exercisers, particularly women. More discouraging is that overweight persons are even less likely to continue a fitness program (Dishman & Ickes, 1981; Brownell & Stunkard, 1980). However, self-reported exercise adherence was high among subjects who participated in the present study's exercise groups, at least during the 3-months of treatment. Notably, ninety percent of exercisers completed the program compared to fifty-five percent of nonexercising subjects. Exercising subjects may have found this particular aspect of the program enjoyable, enhancing their participation in the program as a whole. It is possible that the additional contact with project staff and group members available during initial walking sessions at the track increased subjects involvement and commitment to the program, promoting greater
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long-term program adherence. The utility of periodic booster sessions with novice exercisers may be an important area for exploration in exercise adherence studies conducted with sedentary women. This study differed from most evaluations of the psychological benefits of exercise by employing two very different outcome measures; self-repon questionnaires and daily measures of mood included in eating diaries. Comparison of other prospective measures of affect and exercise related cognitions may yield further information on the process of fitness training. King, Taylor, Haskell and DeBusk (1989) measured multiple psychological variables on individualized-type rating scales in a study of healthy middle aged adults who were randomized to exercising in non-exercising conditions. Only items most closely related to actual physical changes associated with exercise showed improvement. The present study replicates the findings of Wing et al. (1984) that participation in a behavioral weight control program produces beneficial psychological changes. However, we did not replicate the finding that degree of weight loss was associated with the amount of psychological benefit. More evidence is needed before exercise can be recommended as a specific anxiolytic therapy for sedentary obese. Exercise clearly has physical benefits for obese women wishing to lose weight. However, claims that aerobic exercise will also lead to reductions in anxiety, depression, or other negative affects in obese women who are not physically conditioned are not supported by these data. REFERENCES American Diabetes Association, (1987). Nutritional recommendations and principals for individuals with diabetes mcllitus: 1986. Diabetes Care, 10, 126-132. Blumenthal, J.A., W m s , S., Needel, T.L. & Wallace, A.G. (1982). Psychological and physiological effects of physical condition on the elderly. Journal of P~chosomnricResearch, 26, 505-510. Brownell, K.D. & Stunkard, A.J. (1980). Physical activity in the development and control of obesity. In A.J. Stunkani (Ed.) Obesiry. Philadelphia, PA: W.B. Saunders & Co. Brownell, K.D., Stunkard, A.J. & Albaum, J.M. (1980). Evaluation and modification of exercise palterns in the natural environment. American Journol of Psychiahy, 137, 1540-1545.
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Dahlkoetter, I., Callahan. E.J. & Linton, J. (1979). Obesity and the unbalanced energy equation: exercise versus eating habit change. Journal of Consulting and Clinical Psychology, 47, 5, 898-905. Derogotis, L.R. (197'7). The SCL-90-R: Administration, s w M g and procedures. Manual-I. Baltimore: Clinical Psychometrics Research. Dishman, R.K. & Ickes, W. (1981). Self-motivation and adherence to therapeutic exercise. Journal of Behavioral Medicine, 4, 421438. Dubbert, P.M, Tern, L., Rowland, A.K., Ponetius, J.E. &Krug, L.M. (1988). Relapse in Exercise. Presentation, Society of Behavioral Medicine Annual Convention, April, Boston MA. Folkins, C.H.,Lynch, S. & Gardner, M.M. (1972). Psychological fimess as a function of physical fitness. Archives of Physical Medicine and RehabiIitarion, 53, 503-508. Folkins, C.H. & S h e , W.R. (1981). Physical fitness training and mental health. American Psychologirl, 36, 4, 373-389. Harris, M.B., & Hallbauer, E.S. (1973). Selfdirected weight control through eating and exercise. Behavior Research and nterapy, 11, 523-529. Hill, 1.0.. Schlundt, D.G., Sbrocw, T., Sharp, Teresa, Pope, I.. Stetson. B., Kaler, M. & Heim, C. (1989). Food restriction in obese women: effects of alternating low and moderate caloric intake. Journal of Clinical Nufririon, 50, 2, 248-254. King, A.C., Taylor, C.B., Haskell, W.L.& DeBusk, R.F. (1989). Influence of regular aerobic exercise on psychological health: A randomized, controlled trial of healthy middle aged adults. Kowal, D., Patton, J. & Vogal, J. (1978). Psychological states and aerobic fitness of male and female recruits before and after basic training. Aviation, Space, and Environmental Medicine, 49, 603-606. Lampman, R.M., Schteingart, D.E.& Foss, M.L. (1985). Exercise as a p M therapy for the extremely obese. Medicine and Science in Sports and Grercise, 18, 1. 19-24. Long, B. (1985). Aerobic conditioning and stress inoculation: A comparison of stress-management interventions. Cognitive lherapy and Research, 8, 517542. McCann, I.L. & Holmes, D.S. (1984). Influence of aerobic exercise on dcpression. Journal of Perso~Iityand Social Psychology, 46, 1142-1147. Pem. M.G., McAdoo, W.G., McAlhter, D.A., Lauer, J.B. & Yancey, D.Z. (1986). Enhancing the efficacy of behavior therapy for obesity: Effects of aerobic exercise and a multicomponent maintenance program. Journal of Consulting and Clinical Psychology, 54, 5, 670-675. Schlundt, D.G.. Taylor, D., Hill, J.O., Sbrocco, T., PopaCordle. J., Kasser, T. & Arnold D. (1991). Taxonomy of obese female participants in a weight loss program. American Journal of Clinical Nutrition, 53, 1151-8. Schlundt, D.G., & Z i e M g . R.T., (1988). The dieter's inventory of eating temptations: A measure of weight control wmpetence. Addictive Behaviors, 13, 151-164.
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S h e , W.E. (1984). Rychological benefits of exercise. Advances, 1, 4, 15-29. Soenstroem, R.J. (1984). Exercise and self-esteem. Exercise and Spon Sciences Reviews, 12, 123-155. Stason, B.A. (1991). Development ond evaluation of aprobkm solving and behovioral skills troining program to promote adherence to the lDDM dietary regimen. Doctoral Thesis, Vanderbit University. Stuatt, R.B. (1975). Exercise prescription in weight management: Advantages, bhniques and obstacles. Obesiry/Boriotric Medicine, 4, 16-24. Thompson. I.K., Jarvie, G.J.,Lahey, B.B. & Curetan, K.J. (1982). Exercise and obesity: Etiology, physiology, and intervention. Psychological Bulletin, 91, 1, 55-79.
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