EFFECT OF ABDOMINAL RESISTANCE EXERCISE ON ABDOMINAL SUBCUTANEOUS FAT OF OBESE WOMEN: A RANDOMIZED CONTROLLED TRIAL USING ULTRASOUND IMAGING ASSESSMENTS Ramin Kordi, MD, MS, PhD, a Saeed Dehghani, MD, b Pardis Noormohammadpour, MD, c
Mohsen Rostami, MD, d and Mohammad Ali Mansournia, MD, MPH, PhD e ABSTRACT
Objectives: The aim of this study was to compare the effect of diet and an abdominal resistance training program to diet alone on abdominal subcutaneous fat thickness and waist circumference of overweight and obese women. Methods: This randomized clinical trial included 40 overweight and obese women randomly divided into 2 groups: diet only and diet combined with 12 weeks of abdominal resistance training. Waist and hip circumferences and abdominal skin folds of the subjects were measured at the beginning and 12 weeks after the interventions. In addition, abdominal subcutaneous fat thickness of the subjects was measured using ultrasonography. Percentage body fat and lean body mass of all the subjects were also measured using a bioelectric impedance device. Results: After 12 weeks of intervention, the weight of participants in both groups decreased; but the difference between the 2 groups was not significant (P = .45). Similarly, other variables including abdominal subcutaneous fat, waist circumference, hip circumference, body mass index, body fat percentage, and skin fold thickness were reduced in both groups; but there were no significant differences between the groups. Conclusions: This study found that abdominal resistance training besides diet did not reduce abdominal subcutaneous fat thickness compared to diet alone in overweight or obese women. (J Manipulative Physiol Ther 2014;xx:1-7) Key Indexing Terms: Obesity; Ultrasonography; Resistance Training; Subcutaneous Fat; Abdomen
O
besity is a risk factor for numerous chronic diseases, such as coronary artery disease, diabetes mellitus, some cancers, and musculoskeletal
a Associate Professor, Sports Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Spine Division, Noorafshar Rehabilitation & Sports Medicine Hospital, Tehran, Iran. b Sports Medicine Specialist, Sports Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. c Assistant Professor, Sports Medicine Research Center, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Spine Division, Noorafshar Rehabilitation and Sports Medicine Hospital, Tehran, Iran. d General Practitioner, Sports Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. e Assistant Professor, Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Submit requests for reprints to: Ramin Kordi, MD, MS, PhD, Sport Medicine Research Center, No. 7 Al-e-Ahmad Hwy, Tehran, IR Iran, PO Box: 14395-578. (e-mail: [email protected]). Paper submitted February 25, 2014; in revised form December 8, 2014; accepted December 12, 2014. 0161-4754 Copyright © 2014 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2014.12.004
problems. 1,2 Recent studies have reported an association between body fat distribution and metabolic and circulatory diseases in obesity. 3,4 Studies on this topic showed that people with high waist-to-hip ratio had higher blood pressure, reduced carbohydrate tolerance, higher plasma insulin concentration, and higher risk for stroke and ischemic heart disease. 4–8 Diet and physical activity are suggested as the major tools for the prevention and treatment of obesity. 9 Aerobic activities have been widely studied and recommended for the prevention and treatment of obesity and its comorbidities. 9 In parallel, some authors have investigated the effects of both general and local resistance trainings on obesity. According to these findings, it is reported that general resistance training might increase the lean body mass (LBM) and muscle strength and also could decrease the percentage of body fat (PBF), waist circumference, and visceral and subcutaneous abdominal fat and thigh fat thicknesses. 10–13 However, our finding regarding the effect of local resistance training on the fat reduction of the subjects is limited to a few studies. Kostek et al 14 reported a significant spot fat reduction in arms of male subjects who were asked to perform an upper-body resistance training program. However, analyzing the results of all the subjects (male and female), they found no significant relation. Therefore, they
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concluded that resistance training could not lead to spot fat reduction in the subjects. Some have suggested that the minimum thickness of the abdominal subcutaneous fat layer is significantly related to the femoral artery atherosclerosis. 15 This finding suggests that fat reduction in local areas of the body, particularly in the abdomen, might have importance. According to anecdotal findings, local abdominal resistance training might affect the abdominal subcutaneous fat and therefore could be a part of the management of abdominal obesity. However, to our knowledge, no study has tested this hypothesis. Respecting the higher prevalence of overweightness and obesity in women compared to men, 16 the current study was performed to compare the effect of diet alone (DIET) and diet combined with 12 weeks of abdominal resistance training (DIET + EXE) on abdominal subcutaneous fat thickness in overweight and obese women.
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At the beginning of the study, we estimated subjects’ daily energy (caloric) requirements based on their basal metabolic rate (BMR) and physical activity level. We used the HarrisBenedict equation to calculate BMR. 17 Then, we created 10 kcal/kg (41860 J/Kg) of body weight calorie deficit for each subject. This value of calorie deficit was constant during the study. We calculated the number of food units based on 3 major nutrient groups (55%-65% carbohydrate, 12%-20% proteins, and 20%-35% fat) for each subject. Finally, our nutrition specialist taught subjects the food units and the selection methods among them according to the calculations. In a home-based program, subjects in the DIET + EXE group performed 12 weeks of abdominal resistance training in 3 nonconsecutive days per week. After a light warm-up, subjects performed 2 sets of 8 repetitions of the abdominal crunch, right/ left oblique crunch, abdominal drawing-in, and abdominal bracing. Subjects were instructed to hold each contraction for 5 seconds, and a 2-minute rest followed each set.
METHODS The design of the study was single-blind randomized controlled trial.
Participants The inclusion criteria were as follows: (1) adult women with age of 18 years or more; (2) overweight or obese subjects (body mass index [BMI] N 25 kg/m 2); (3) no history of regular endurance or resistance training during the last 180 days; (4) not pregnant; (5) no smoking history in the recent 6 months; (6) no systemic diseases that might affect the diet, resistance training, or musculoskeletal functions; and (7) no significant weight loss in the recent 6 months (N 10% body weight). In addition, the exclusion criteria were as follows: (1) using products that might affect the body weight or abdominal subcutaneous fat such as laser, vacuum, ultrasound modality, acupuncture, cream products, gel products, massage, and drugs; (2) any sicknesses that could affect the diet or resistance training; (3) getting pregnant during the study. This study was performed at Sports Medicine Research Center at Tehran University of Medical Sciences. This study was approved by the ethics committee of Vice Chancellor of Research of Tehran University of Medical Sciences. The study was registered as number “IRCT138812182973N2” at a registry of nationally and privately supported clinical trials (ie, Irct.ir). Participants provided consent to be a part of this study.
Interventions Subjects were randomly recruited into 2 groups using a computer-generated random number list. Our clinical assessor was not aware of the allocation of the subjects in the study groups. Subjects were randomly allocated into the 2 following groups: DIET and DIET + EXE.
Outcomes We measured subject’s height, body weight, waist circumference, PBF, abdominal subcutaneous fat, and skin fold thickness in the first visit and 12 weeks later. 18 The subjects were asked to take and hold a deep breath; and while they were barefoot and looking straight ahead, the assessor recorded their height in centimeters. We also measured the body weight of the subjects with an accuracy of 0.1 kg by a digital scale. We measured the waist circumference at the smallest area of the waist between the lower costal border and the iliac crest while the subjects were standing upright and relaxed. In addition, we measured the hip circumference around the largest area of the hips and buttocks. The measured values were recorded at the end of a normal exhalation without pulling the tape tightly. The PBF was measured for all subjects using the bioelectrical impedance analysis method (AVIS33 body composition analyzer; Jawon Medical Co Ltd, Kyungsang Bukdo, South Korea). Under the standard protocol for use of body composition analyzer, the subjects were asked not to drink or eat anything during the last 4 hours before the test. They were also asked to perform no exercise and receive no diuretics during the 12 hours before the test. In addition, immediately before the tests, the subjects were asked to empty their bladder. 19 Abdominal subcutaneous fat thickness was measured while the subject was placed in a supine position, keeping her shoulders, buttocks, and heels in touch with the table. 4,12,20 As ultrasonography has been accepted to be an appropriate noninvasive and reliable device for measuring abdominal subcutaneous fat, 21,22 we used ultrasound assessment of the subjects to measure their subcutaneous fat thickness. A Sonosite MicroMaxx ultrasound machine (Sonosite Inc, Bothell, WA) and a linear transducer (HFL38/6-13 MHz) were used to record the abdominal subcutaneous fat thicknesses in B-mode format. The transducer was positioned in transverse plane, and measurement of subcutaneous fat
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thickness was made at the center point of the image using the caliper of the machine. The distance between the top of inferior facial layer and bottom of cutaneous layer was considered as subcutaneous fat thickness. The transducer position was 2.5 cm toward the right lateral side of the umbilicus (midpoint of the navel). 23 The angle of probe was perpendicular to the skin. Adequate water-soluble ultrasound gel was applied to the transducer head to increase the area of contact, and then the transducer head was placed at the skin as lightly as possible to avoid compression of fat layers. 4 Skin fold thickness was measured by a standard skin fold caliper (Harpenden caliper; British Indicators Ltd, Burgess Hill, UK; with 0.1-mm accuracy). 24 For measurement of the skin fold thickness, while subjects were relaxed and standing upright, a well-experienced tester grasped a fold of skin tightly between the thumb and index finger of his left hand and lifted it away from the body. He rolled the fold to ensure that subcutaneous tissue (not muscles) were being measured; then the jaws of the caliper were positioned over the skin fold just 1 cm under his fingers. After releasing the grip, the tester waited 1 to 2 seconds and then read the caliper. The measurement was performed at the abdominal site in a raised vertical fold 2 cm toward the right lateral side of the umbilicus (midpoint of the navel). The tester carried out the measurement for 3 times; and in case of variations of more than 3 mm in the 3 mentioned values, measurement for the fourth time was performed. 25
Statistical Methods Sample size calculation of the study was done based on the detection of 1.5-cm difference in waist circumference (α= 0.05 and β= 0.2) of the subjects. It was calculated that 14 subjects were required in each group of the study; and considering a 30% dropout probability, 20 subjects were finally recruited in each group of the study (40 participants). Mean values and standard deviations were calculated for age, weight, height, waist circumference, hip circumference, BMI, PBF, abdominal subcutaneous fat thickness, skin fold thickness, and LBM. To decrease the effects of confounding factors such as age and height on the analysis of obtained alterations in the mentioned physical variables between the groups, using analysis of covariance test, the results of the comparison between the groups were statistically adjusted for these variables. A P value less than .05 was considered as significant.
RESULTS In total, 52 volunteer overweight or obese women initially enrolled in the study. Twelve subjects did not meet the inclusion criteria (Fig 1). Forty subjects were randomly assigned equally to 2 groups of the study. During the follow-up, 4 individuals from the DIET group and 6 participants from the DIET + EXE group withdrew from the study. Regarding the number of participants who discontinue the study, there was no significant difference between
Kordi et al Effect of Abdominal Exercise on Fat
the groups. The remaining 30 participants including 16 subjects in the DIET group and 14 in the DIET + EXE group finished the 12-week course of the study, and their data were included in the final analysis. The demographic data of participants are provided in Table 1. There were no considerable differences among the basic characteristics of participants in the 2 groups. The measured physical variables of subjects at the baseline and after the course of the study are presented in Table 2. Changes of the measured physical variables of subjects during the course of study are presented in Table 3. It is shown that weight, abdominal subcutaneous fat, waist circumference, hip circumference, BMI, PBF, and skin fold thickness were reduced in both groups, but there was no significant difference between the groups. The subjects reported no important adverse events or side effects during the course of study.
DISCUSSION Body fat distribution has a considerable role in the management of obesity and its complications. 7,8 It has been reported that general resistance training besides caloric restriction would be an effective strategy to mobilize trunk fat mass and particularly abdominal subcutaneous fat mass. 26 However, our results indicated that, after 12 weeks of intervention, reductions of some variables including weight, abdominal subcutaneous fat thickness, BMI, waist circumference, skin fold thickness, and PBF in the diet plus local abdominal resistance exercise group were more than those in the diet-only group, but these differences were not significant. Therefore, when abdominal resistance training is added to diet in the short term, it could not effectively decrease abdominal subcutaneous fat thickness compared to diet alone.
Weight and BMI Effect of resistance training on weight reduction of overweight and obese people is a controversial topic. Concerning the effect of general resistance training programs, some studies have reported significant reduction in weight and BMI in overweight and obese patients after these exercises. 27–29 However, other studies 10–12,30–32 did not find a significant reduction in weight and BMI of the subjects using these exercise programs, which might be due to replacement of some part of the fat by the LBM. Regarding local resistance training, to our knowledge, no study has reported the effect of these exercises on weight and BMI reduction. Our study results showed that abdominal resistance training has no significant effect on weight and BMI reduction. This might be because abdominal muscles are mainly stabilizer muscles and therefore their training could lead to small effects on BMR, energy expenditure, and weight. On the other hand, prior to puberty, females and
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Fig 1. Flow diagram of the progress through the phases of the study. males have similar muscle mass and strength; and after puberty, girls’ strength and muscle mass do not change appreciably, probably because of hormonal mechanisms. 33 Therefore, local resistance training might have small effects on muscle mass in women.
Abdominal Subcutaneous Fat Thickness and Skin Fold Thickness Kostek et al 14 reported that as a result of local resistance training in a region, spot fat reduction does not occur. Similarly, we did not find a significant effect of abdominal resistance training on abdominal subcutaneous fat thickness reduction. However, Brochu et al 26observed significant decreases in the trunk subcutaneous fat thickness (superficial and deep layers) among caloric restriction and general resistance training group in overweight and obese postmenopausal women.
Waist and Hip Circumference About waist and hip circumference, Brochu et al 26 have shown that the group with caloric restriction in combination with general resistance training displayed significantly greater decrease for hip and waist circumference compared with the caloric restriction–only group. In this study, subjects in the DIET + EXE group had a greater reduction in the waist circumference and lesser reduction in hip circumference compared with the DIET group; however, the difference between the groups was not significant.
Table 1. The Basic Characteristics of Recruited Participants in the Study Group Age, y
DIET DIET + EXE Height, cm DIET DIET + EXE
Number Mean
Standard Deviation Min-Max
16 14 16 14
15.1 14.4 6.7 5.0
43.0 42.2 158.2 157.4
21-72 18-62 150-173 167-145
DIET, diet only group; DIET+EXE, diet combined with abdominal resistance training. The differences between none of the values were statistically significant.
PBF and LBM Reduction of PBF by general resistance training has been shown in a number of studies. 26,29,34 However, finding no significant relation in the PBF of the subjects in this study might be because of a small amount of abdominal muscle that was involved in the prescribed resistance trainings compared with previous studies that used a general resistance training for their subjects. 32 In some studies, 29,35 an increased LBM after general resistance training is reported; however, in other studies, 26,32 LBM has not been changed by these exercise trainings. In addition, Campbell et al 36 and Hunter et al 37 reported that LBM decreased in the control group and was unchanged in those who participated in a resistance training program. We found no significant difference in the decrease of the LBM between the 2 groups of the study.
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Table 2. Measured Variables at the Baseline and 12th Week in the DIET Group and DIET + EXE Group Variable
Group
Week 0 Mean (SD)
Week 12 Mean (SD)
P Value
Weight (kg)
DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE
78.7 (12.6) 76.8 (9.7) 93.8 (14.5) 96.7 (10.9) 109.8 (9.2) 106.6 (7.1) 0.9 (0.09) 0.9 (0.09) 31.5 (4.4) 31.6 (4.7) 38.7 (4.2) 39.2 (4.2) 47.9 (5.9) 47.1 (5.0) 33.5 (9.6) 36.4 (12.4) 41.4 (13.6) 42.7 (10.0)
76.6 (13.4) 74.1 (10.0) 89.4 (14.0) 90.9 (8.4) 106.2 (6.2) 103.6 (7.1) 0.83 (0.09) 0.87 (0.07) 30.4 (4.7) 29.9 (3.8) 37.0 (4.3) 37.0 (3.5) 47.9 (6.5) 46.1 (4.7) 30.2 (8.1) 33.0 (16.1) 38.3 (14.0) 37.5 (8.8)
.003 a b .001 a .001 a .013 a .016 a .007 a .27 .054 .000 a .020 a b .001 a .003 a .91 .058 .048 a .098 .042 a .031 a
Waist circumference (cm) Hip circumference (cm) Waist-to-hip ratio BMI (kg/m2) PBF Percentage of LBM Abdominal subcutaneous fat thickness (mm) Skin fold thickness measured by caliper (mm)
BMI, body mass index; DIET, diet only group; DIET+EXE, diet combined with abdominal resistance training; LBM, lean body mass; PBF, percent body fat. a Statistically significant.
Table 3. Comparison Between the Changes of Physical Variables During the Study (Weeks 0 and 12) Among the Participants in 2 Groups. Variables
DIET DIET + EXE Mean Dif (SD) a Mean Dif (SD) a P Value
Weight (kg) − 2.1±2.3 Waist circumference (cm) − 4.3±4.3 Hip circumference (cm) − 3.5±5.2 − 1.0±0.9 BMI (kg/m2) PBF − 1.7±1.2 Abdominal subcutaneous − 2.7±4.7 fat thickness (mm) Skin fold thickness (mm) − 3.1±5.6 − 0.05±1.8 LBM (kg/m2)
− 2.7±2.0 − 5.7±7.4 − 2.9±3.4 − 1.6±2.4 − 2.2±2.2 − 3.7±7.2
.44 .49 .43 .29 .49 .60
− 5.1±8.0 − 0.9±1.6
.34 .15
BMI, body mass index; DIET, diet only group; DIET+EXE, diet combined with abdominal resistance training; LBM, lean body mass; PBF, percent body fat. a Difference between the mean of variables at the baseline and after 12 weeks of the study.
LIMITATIONS There are limitations to this study, which limit the generalizability of the study findings. The muscle size and strength of the subjects were not considered in the outcome measurements of the study. In addition, there was no control on the level of physical activity of the subjects in the study period. The small sample size of the study can also be considered as another limitation of the study. Finally, 10 subjects (25%) left the study, which is a high rate of loss to follow-up.
CONCLUSION This study showed that when abdominal resistance training is added to diet, there were no short-term effects on
abdominal subcutaneous fat thickness compared to diet alone for overweight or obese women.
FUNDING SOURCES AND POTENTIAL CONFLICTS OF INTEREST This research was supported by a Tehran University of Medical Sciences & Health Services grant. No conflicts of interest were reported for this study.
CONTRIBUTORSHIP INFORMATION Concept development (provided idea for the research): R.K., P.N., S.D. Design (planned the methods to generate the results): R.K., P.N., S.D. Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): R.K., P.N., S.D. Data collection/processing (responsible for experiments, patient management, organization, or reporting data): P.N., S.D., M.R., M.A.M. Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): S.D., M.R., M.A.M. Literature search (performed the literature search): P.N., S.D., M.R. Writing (responsible for writing a substantive part of the manuscript): P.N., M.R. Critical review (revised manuscript for intellectual content; this does not relate to spelling and grammar checking): P.N., M.R.
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Practical Application • This study showed that short-term abdominal resistance training in addition to diet it did not reduce abdominal subcutaneous fat thickness compared to diet alone in overweight or obese women.
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13. Park SK, Park JH, Kwon YC, Kim HS, Yoon MS, Park HT. The effect of combined aerobic and resistance exercise training on abdominal fat in obese middle-aged women. J Physiol Anthropol Appl Human Sci 2003;22(3):129-35. 14. Kostek MA, Pescatello LS, Seip RL, et al. Subcutaneous fat alterations resulting from an upper-body resistance training program. Med Sci Sports Exerc 2007;39(7):1177-85. 15. Tsitsilonis S, Vlachos IS, Bampali A, Revenas K, Votteas V, Perrea DN. Sonographic measurements of subcutaneous fat in obese individuals may correlate better with peripheral artery disease indices. J Clin Ultrasound 2009;37(5):263-9. 16. Rashidy-Pour A, Malek M, Eskandarian R, Ghorbani R. Obesity in the Iranian population. Obes Rev 2009;10(1):2-6. 17. Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci U S A 1918;4(12):370-3. 18. Armstrong L, Whaley M, Brubaker P, Otto R. Health-related physical fitness testing and interpretation. In: ACSM’s Guidelines for Exercise Testing and Prescription. Philadelphia, PA: Lippincott Williams and Wilkins; 2006. p. 55-92. 19. Ratamess N. Body composition status and assessment. In: Ehrman JK, deJong A, Sanderson B, Swain D, Swank A, Womack C, editors. ACSM’s Resource Manual for Guidelines for Exercise Testing and Prescription. Philadelphia, PA: Lippincott Williams & Wilkins; 2010. p. 264-81. 20. Armellini F, Zamboni M, Rigo L, et al. The contribution of sonography to the measurement of intra-abdominal fat. J Clin Ultrasound 1990;18:563-7. 21. Fanelli MT, Kuczmarski RJ. Ultrasound as an approach to assessing body composition. Am J Clin Nutr 1984;39(5):703-9. 22. Armellini F, Zamboni M, Rigo L, et al. Sonography detection of small intra-abdominal fat variations. Int J Obes 1991;15: 847-52. 23. Saito K, Nakaji S, Umeda T, Shimoyama T, Sugawara K, Yamamoto Y. Development of predictive equations for body density of sumo wrestlers using B-mode ultrasound for the determination of subcutaneous fat thickness. Br J Sports Med 2003;37(2):144-8. 24. Yajnik CS, Lubree HG, Rege SS, et al. Adiposity and hyperinsulinemia in Indians are present at birth. J Clin Endocrinol Metab 2002;87(12):5575-80. 25. Ratamess N. Body composition status and assessment. In: Swain DP, editor. ACSM’s Resource Manual for Guidelines for Exercise Testing and Prescription. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2014. p. 287-308. 26. Brochu M, Malita MF, Messier V, et al. Resistance training does not contribute to improving the metabolic profile after a 6-month weight loss program in overweight and obese postmenopausal women. J Clin Endocrinol Metab 2009; 94(9):3226-33. 27. Winnick JJ, Gaillard T, Schuster DP. Resistance training differentially affects weight loss and glucose metabolism of white and African American patients with type 2 diabetes mellitus. Ethn Dis 2008;18(2):152-6. 28. Wycherley TP, Noakes M, Clifton PM, Cleanthous X, Keogh JB, Brinkworth GD. A high-protein diet with resistance exercise training improves weight loss and body composition in overweight and obese patients with type 2 diabetes. Diabetes Care 2010;33(5):969-76. 29. Daly RM, Dunstan DW, Owen N, Jolley D, Shaw JE, Zimmet PZ. Does high-intensity resistance training maintain bone mass during moderate weight loss in older overweight adults with type 2 diabetes? Osteoporos Int 2005;16(12):1703-12. 30. Gornall J, Villani RG. Short-term changes in body composition and metabolism with severe dieting and resistance exercise. Int J Sport Nutr 1996;6(3):285-94.
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31. Avila JJ, Gutierres JA, Sheehy ME, Lofgren IE, Delmonico MJ. Effect of moderate intensity resistance training during weight loss on body composition and physical performance in overweight older adults. Eur J Appl Physiol 2010;109(3):517-25. 32. Joseph LJ, Trappe TA, Farrell PA, et al. Short-term moderate weight loss and resistance training do not affect insulinstimulated glucose disposal in postmenopausal women. Diabetes Care 2001;24(11):1863-9. 33. Birrer RB, O'Connor FG. Sports Medicine for the Primary Care Physician. 3rd ed. Boca Raton, LA: Taylor and Francis; 2004. 34. Nakata Y, Ohkawara K, Lee DJ, Okura T, Tanaka K. Effects of additional resistance training during diet-induced weight
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loss on bone mineral density in overweight premenopausal women. J Bone Miner Metab 2008;26(2):172-7. 35. Castaneda C, Layne JE, Munoz-Orians L, et al. A randomized controlled trial of resistance exercise training to improve glycemic control in older adults with type 2 diabetes. Diabetes Care 2002;25(12):2335-41. 36. Campbell WW, Haub MD, Wolfe RR, et al. Resistance training preserves fat-free mass without impacting changes in protein metabolism after weight loss in older women. Obesity (Silver Spring) 2009;17(7):1332-9. 37. Hunter GR, Byrne NM, Sirikul B, et al. Resistance training conserves fat-free mass and resting energy expenditure following weight loss. Obesity (Silver Spring) 2008;16(5):1045-51.
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Mohsen Rostami, MD, d and Mohammad Ali Mansournia, MD, MPH, PhD e ABSTRACT
Objectives: The aim of this study was to compare the effect of diet and an abdominal resistance training program to diet alone on abdominal subcutaneous fat thickness and waist circumference of overweight and obese women. Methods: This randomized clinical trial included 40 overweight and obese women randomly divided into 2 groups: diet only and diet combined with 12 weeks of abdominal resistance training. Waist and hip circumferences and abdominal skin folds of the subjects were measured at the beginning and 12 weeks after the interventions. In addition, abdominal subcutaneous fat thickness of the subjects was measured using ultrasonography. Percentage body fat and lean body mass of all the subjects were also measured using a bioelectric impedance device. Results: After 12 weeks of intervention, the weight of participants in both groups decreased; but the difference between the 2 groups was not significant (P = .45). Similarly, other variables including abdominal subcutaneous fat, waist circumference, hip circumference, body mass index, body fat percentage, and skin fold thickness were reduced in both groups; but there were no significant differences between the groups. Conclusions: This study found that abdominal resistance training besides diet did not reduce abdominal subcutaneous fat thickness compared to diet alone in overweight or obese women. (J Manipulative Physiol Ther 2014;xx:1-7) Key Indexing Terms: Obesity; Ultrasonography; Resistance Training; Subcutaneous Fat; Abdomen
O
besity is a risk factor for numerous chronic diseases, such as coronary artery disease, diabetes mellitus, some cancers, and musculoskeletal
a Associate Professor, Sports Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran; Spine Division, Noorafshar Rehabilitation & Sports Medicine Hospital, Tehran, Iran. b Sports Medicine Specialist, Sports Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. c Assistant Professor, Sports Medicine Research Center, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran; Spine Division, Noorafshar Rehabilitation and Sports Medicine Hospital, Tehran, Iran. d General Practitioner, Sports Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. e Assistant Professor, Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. Submit requests for reprints to: Ramin Kordi, MD, MS, PhD, Sport Medicine Research Center, No. 7 Al-e-Ahmad Hwy, Tehran, IR Iran, PO Box: 14395-578. (e-mail: [email protected]). Paper submitted February 25, 2014; in revised form December 8, 2014; accepted December 12, 2014. 0161-4754 Copyright © 2014 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2014.12.004
problems. 1,2 Recent studies have reported an association between body fat distribution and metabolic and circulatory diseases in obesity. 3,4 Studies on this topic showed that people with high waist-to-hip ratio had higher blood pressure, reduced carbohydrate tolerance, higher plasma insulin concentration, and higher risk for stroke and ischemic heart disease. 4–8 Diet and physical activity are suggested as the major tools for the prevention and treatment of obesity. 9 Aerobic activities have been widely studied and recommended for the prevention and treatment of obesity and its comorbidities. 9 In parallel, some authors have investigated the effects of both general and local resistance trainings on obesity. According to these findings, it is reported that general resistance training might increase the lean body mass (LBM) and muscle strength and also could decrease the percentage of body fat (PBF), waist circumference, and visceral and subcutaneous abdominal fat and thigh fat thicknesses. 10–13 However, our finding regarding the effect of local resistance training on the fat reduction of the subjects is limited to a few studies. Kostek et al 14 reported a significant spot fat reduction in arms of male subjects who were asked to perform an upper-body resistance training program. However, analyzing the results of all the subjects (male and female), they found no significant relation. Therefore, they
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concluded that resistance training could not lead to spot fat reduction in the subjects. Some have suggested that the minimum thickness of the abdominal subcutaneous fat layer is significantly related to the femoral artery atherosclerosis. 15 This finding suggests that fat reduction in local areas of the body, particularly in the abdomen, might have importance. According to anecdotal findings, local abdominal resistance training might affect the abdominal subcutaneous fat and therefore could be a part of the management of abdominal obesity. However, to our knowledge, no study has tested this hypothesis. Respecting the higher prevalence of overweightness and obesity in women compared to men, 16 the current study was performed to compare the effect of diet alone (DIET) and diet combined with 12 weeks of abdominal resistance training (DIET + EXE) on abdominal subcutaneous fat thickness in overweight and obese women.
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At the beginning of the study, we estimated subjects’ daily energy (caloric) requirements based on their basal metabolic rate (BMR) and physical activity level. We used the HarrisBenedict equation to calculate BMR. 17 Then, we created 10 kcal/kg (41860 J/Kg) of body weight calorie deficit for each subject. This value of calorie deficit was constant during the study. We calculated the number of food units based on 3 major nutrient groups (55%-65% carbohydrate, 12%-20% proteins, and 20%-35% fat) for each subject. Finally, our nutrition specialist taught subjects the food units and the selection methods among them according to the calculations. In a home-based program, subjects in the DIET + EXE group performed 12 weeks of abdominal resistance training in 3 nonconsecutive days per week. After a light warm-up, subjects performed 2 sets of 8 repetitions of the abdominal crunch, right/ left oblique crunch, abdominal drawing-in, and abdominal bracing. Subjects were instructed to hold each contraction for 5 seconds, and a 2-minute rest followed each set.
METHODS The design of the study was single-blind randomized controlled trial.
Participants The inclusion criteria were as follows: (1) adult women with age of 18 years or more; (2) overweight or obese subjects (body mass index [BMI] N 25 kg/m 2); (3) no history of regular endurance or resistance training during the last 180 days; (4) not pregnant; (5) no smoking history in the recent 6 months; (6) no systemic diseases that might affect the diet, resistance training, or musculoskeletal functions; and (7) no significant weight loss in the recent 6 months (N 10% body weight). In addition, the exclusion criteria were as follows: (1) using products that might affect the body weight or abdominal subcutaneous fat such as laser, vacuum, ultrasound modality, acupuncture, cream products, gel products, massage, and drugs; (2) any sicknesses that could affect the diet or resistance training; (3) getting pregnant during the study. This study was performed at Sports Medicine Research Center at Tehran University of Medical Sciences. This study was approved by the ethics committee of Vice Chancellor of Research of Tehran University of Medical Sciences. The study was registered as number “IRCT138812182973N2” at a registry of nationally and privately supported clinical trials (ie, Irct.ir). Participants provided consent to be a part of this study.
Interventions Subjects were randomly recruited into 2 groups using a computer-generated random number list. Our clinical assessor was not aware of the allocation of the subjects in the study groups. Subjects were randomly allocated into the 2 following groups: DIET and DIET + EXE.
Outcomes We measured subject’s height, body weight, waist circumference, PBF, abdominal subcutaneous fat, and skin fold thickness in the first visit and 12 weeks later. 18 The subjects were asked to take and hold a deep breath; and while they were barefoot and looking straight ahead, the assessor recorded their height in centimeters. We also measured the body weight of the subjects with an accuracy of 0.1 kg by a digital scale. We measured the waist circumference at the smallest area of the waist between the lower costal border and the iliac crest while the subjects were standing upright and relaxed. In addition, we measured the hip circumference around the largest area of the hips and buttocks. The measured values were recorded at the end of a normal exhalation without pulling the tape tightly. The PBF was measured for all subjects using the bioelectrical impedance analysis method (AVIS33 body composition analyzer; Jawon Medical Co Ltd, Kyungsang Bukdo, South Korea). Under the standard protocol for use of body composition analyzer, the subjects were asked not to drink or eat anything during the last 4 hours before the test. They were also asked to perform no exercise and receive no diuretics during the 12 hours before the test. In addition, immediately before the tests, the subjects were asked to empty their bladder. 19 Abdominal subcutaneous fat thickness was measured while the subject was placed in a supine position, keeping her shoulders, buttocks, and heels in touch with the table. 4,12,20 As ultrasonography has been accepted to be an appropriate noninvasive and reliable device for measuring abdominal subcutaneous fat, 21,22 we used ultrasound assessment of the subjects to measure their subcutaneous fat thickness. A Sonosite MicroMaxx ultrasound machine (Sonosite Inc, Bothell, WA) and a linear transducer (HFL38/6-13 MHz) were used to record the abdominal subcutaneous fat thicknesses in B-mode format. The transducer was positioned in transverse plane, and measurement of subcutaneous fat
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thickness was made at the center point of the image using the caliper of the machine. The distance between the top of inferior facial layer and bottom of cutaneous layer was considered as subcutaneous fat thickness. The transducer position was 2.5 cm toward the right lateral side of the umbilicus (midpoint of the navel). 23 The angle of probe was perpendicular to the skin. Adequate water-soluble ultrasound gel was applied to the transducer head to increase the area of contact, and then the transducer head was placed at the skin as lightly as possible to avoid compression of fat layers. 4 Skin fold thickness was measured by a standard skin fold caliper (Harpenden caliper; British Indicators Ltd, Burgess Hill, UK; with 0.1-mm accuracy). 24 For measurement of the skin fold thickness, while subjects were relaxed and standing upright, a well-experienced tester grasped a fold of skin tightly between the thumb and index finger of his left hand and lifted it away from the body. He rolled the fold to ensure that subcutaneous tissue (not muscles) were being measured; then the jaws of the caliper were positioned over the skin fold just 1 cm under his fingers. After releasing the grip, the tester waited 1 to 2 seconds and then read the caliper. The measurement was performed at the abdominal site in a raised vertical fold 2 cm toward the right lateral side of the umbilicus (midpoint of the navel). The tester carried out the measurement for 3 times; and in case of variations of more than 3 mm in the 3 mentioned values, measurement for the fourth time was performed. 25
Statistical Methods Sample size calculation of the study was done based on the detection of 1.5-cm difference in waist circumference (α= 0.05 and β= 0.2) of the subjects. It was calculated that 14 subjects were required in each group of the study; and considering a 30% dropout probability, 20 subjects were finally recruited in each group of the study (40 participants). Mean values and standard deviations were calculated for age, weight, height, waist circumference, hip circumference, BMI, PBF, abdominal subcutaneous fat thickness, skin fold thickness, and LBM. To decrease the effects of confounding factors such as age and height on the analysis of obtained alterations in the mentioned physical variables between the groups, using analysis of covariance test, the results of the comparison between the groups were statistically adjusted for these variables. A P value less than .05 was considered as significant.
RESULTS In total, 52 volunteer overweight or obese women initially enrolled in the study. Twelve subjects did not meet the inclusion criteria (Fig 1). Forty subjects were randomly assigned equally to 2 groups of the study. During the follow-up, 4 individuals from the DIET group and 6 participants from the DIET + EXE group withdrew from the study. Regarding the number of participants who discontinue the study, there was no significant difference between
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the groups. The remaining 30 participants including 16 subjects in the DIET group and 14 in the DIET + EXE group finished the 12-week course of the study, and their data were included in the final analysis. The demographic data of participants are provided in Table 1. There were no considerable differences among the basic characteristics of participants in the 2 groups. The measured physical variables of subjects at the baseline and after the course of the study are presented in Table 2. Changes of the measured physical variables of subjects during the course of study are presented in Table 3. It is shown that weight, abdominal subcutaneous fat, waist circumference, hip circumference, BMI, PBF, and skin fold thickness were reduced in both groups, but there was no significant difference between the groups. The subjects reported no important adverse events or side effects during the course of study.
DISCUSSION Body fat distribution has a considerable role in the management of obesity and its complications. 7,8 It has been reported that general resistance training besides caloric restriction would be an effective strategy to mobilize trunk fat mass and particularly abdominal subcutaneous fat mass. 26 However, our results indicated that, after 12 weeks of intervention, reductions of some variables including weight, abdominal subcutaneous fat thickness, BMI, waist circumference, skin fold thickness, and PBF in the diet plus local abdominal resistance exercise group were more than those in the diet-only group, but these differences were not significant. Therefore, when abdominal resistance training is added to diet in the short term, it could not effectively decrease abdominal subcutaneous fat thickness compared to diet alone.
Weight and BMI Effect of resistance training on weight reduction of overweight and obese people is a controversial topic. Concerning the effect of general resistance training programs, some studies have reported significant reduction in weight and BMI in overweight and obese patients after these exercises. 27–29 However, other studies 10–12,30–32 did not find a significant reduction in weight and BMI of the subjects using these exercise programs, which might be due to replacement of some part of the fat by the LBM. Regarding local resistance training, to our knowledge, no study has reported the effect of these exercises on weight and BMI reduction. Our study results showed that abdominal resistance training has no significant effect on weight and BMI reduction. This might be because abdominal muscles are mainly stabilizer muscles and therefore their training could lead to small effects on BMR, energy expenditure, and weight. On the other hand, prior to puberty, females and
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Fig 1. Flow diagram of the progress through the phases of the study. males have similar muscle mass and strength; and after puberty, girls’ strength and muscle mass do not change appreciably, probably because of hormonal mechanisms. 33 Therefore, local resistance training might have small effects on muscle mass in women.
Abdominal Subcutaneous Fat Thickness and Skin Fold Thickness Kostek et al 14 reported that as a result of local resistance training in a region, spot fat reduction does not occur. Similarly, we did not find a significant effect of abdominal resistance training on abdominal subcutaneous fat thickness reduction. However, Brochu et al 26observed significant decreases in the trunk subcutaneous fat thickness (superficial and deep layers) among caloric restriction and general resistance training group in overweight and obese postmenopausal women.
Waist and Hip Circumference About waist and hip circumference, Brochu et al 26 have shown that the group with caloric restriction in combination with general resistance training displayed significantly greater decrease for hip and waist circumference compared with the caloric restriction–only group. In this study, subjects in the DIET + EXE group had a greater reduction in the waist circumference and lesser reduction in hip circumference compared with the DIET group; however, the difference between the groups was not significant.
Table 1. The Basic Characteristics of Recruited Participants in the Study Group Age, y
DIET DIET + EXE Height, cm DIET DIET + EXE
Number Mean
Standard Deviation Min-Max
16 14 16 14
15.1 14.4 6.7 5.0
43.0 42.2 158.2 157.4
21-72 18-62 150-173 167-145
DIET, diet only group; DIET+EXE, diet combined with abdominal resistance training. The differences between none of the values were statistically significant.
PBF and LBM Reduction of PBF by general resistance training has been shown in a number of studies. 26,29,34 However, finding no significant relation in the PBF of the subjects in this study might be because of a small amount of abdominal muscle that was involved in the prescribed resistance trainings compared with previous studies that used a general resistance training for their subjects. 32 In some studies, 29,35 an increased LBM after general resistance training is reported; however, in other studies, 26,32 LBM has not been changed by these exercise trainings. In addition, Campbell et al 36 and Hunter et al 37 reported that LBM decreased in the control group and was unchanged in those who participated in a resistance training program. We found no significant difference in the decrease of the LBM between the 2 groups of the study.
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Table 2. Measured Variables at the Baseline and 12th Week in the DIET Group and DIET + EXE Group Variable
Group
Week 0 Mean (SD)
Week 12 Mean (SD)
P Value
Weight (kg)
DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE DIET DIET + EXE
78.7 (12.6) 76.8 (9.7) 93.8 (14.5) 96.7 (10.9) 109.8 (9.2) 106.6 (7.1) 0.9 (0.09) 0.9 (0.09) 31.5 (4.4) 31.6 (4.7) 38.7 (4.2) 39.2 (4.2) 47.9 (5.9) 47.1 (5.0) 33.5 (9.6) 36.4 (12.4) 41.4 (13.6) 42.7 (10.0)
76.6 (13.4) 74.1 (10.0) 89.4 (14.0) 90.9 (8.4) 106.2 (6.2) 103.6 (7.1) 0.83 (0.09) 0.87 (0.07) 30.4 (4.7) 29.9 (3.8) 37.0 (4.3) 37.0 (3.5) 47.9 (6.5) 46.1 (4.7) 30.2 (8.1) 33.0 (16.1) 38.3 (14.0) 37.5 (8.8)
.003 a b .001 a .001 a .013 a .016 a .007 a .27 .054 .000 a .020 a b .001 a .003 a .91 .058 .048 a .098 .042 a .031 a
Waist circumference (cm) Hip circumference (cm) Waist-to-hip ratio BMI (kg/m2) PBF Percentage of LBM Abdominal subcutaneous fat thickness (mm) Skin fold thickness measured by caliper (mm)
BMI, body mass index; DIET, diet only group; DIET+EXE, diet combined with abdominal resistance training; LBM, lean body mass; PBF, percent body fat. a Statistically significant.
Table 3. Comparison Between the Changes of Physical Variables During the Study (Weeks 0 and 12) Among the Participants in 2 Groups. Variables
DIET DIET + EXE Mean Dif (SD) a Mean Dif (SD) a P Value
Weight (kg) − 2.1±2.3 Waist circumference (cm) − 4.3±4.3 Hip circumference (cm) − 3.5±5.2 − 1.0±0.9 BMI (kg/m2) PBF − 1.7±1.2 Abdominal subcutaneous − 2.7±4.7 fat thickness (mm) Skin fold thickness (mm) − 3.1±5.6 − 0.05±1.8 LBM (kg/m2)
− 2.7±2.0 − 5.7±7.4 − 2.9±3.4 − 1.6±2.4 − 2.2±2.2 − 3.7±7.2
.44 .49 .43 .29 .49 .60
− 5.1±8.0 − 0.9±1.6
.34 .15
BMI, body mass index; DIET, diet only group; DIET+EXE, diet combined with abdominal resistance training; LBM, lean body mass; PBF, percent body fat. a Difference between the mean of variables at the baseline and after 12 weeks of the study.
LIMITATIONS There are limitations to this study, which limit the generalizability of the study findings. The muscle size and strength of the subjects were not considered in the outcome measurements of the study. In addition, there was no control on the level of physical activity of the subjects in the study period. The small sample size of the study can also be considered as another limitation of the study. Finally, 10 subjects (25%) left the study, which is a high rate of loss to follow-up.
CONCLUSION This study showed that when abdominal resistance training is added to diet, there were no short-term effects on
abdominal subcutaneous fat thickness compared to diet alone for overweight or obese women.
FUNDING SOURCES AND POTENTIAL CONFLICTS OF INTEREST This research was supported by a Tehran University of Medical Sciences & Health Services grant. No conflicts of interest were reported for this study.
CONTRIBUTORSHIP INFORMATION Concept development (provided idea for the research): R.K., P.N., S.D. Design (planned the methods to generate the results): R.K., P.N., S.D. Supervision (provided oversight, responsible for organization and implementation, writing of the manuscript): R.K., P.N., S.D. Data collection/processing (responsible for experiments, patient management, organization, or reporting data): P.N., S.D., M.R., M.A.M. Analysis/interpretation (responsible for statistical analysis, evaluation, and presentation of the results): S.D., M.R., M.A.M. Literature search (performed the literature search): P.N., S.D., M.R. Writing (responsible for writing a substantive part of the manuscript): P.N., M.R. Critical review (revised manuscript for intellectual content; this does not relate to spelling and grammar checking): P.N., M.R.
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Practical Application • This study showed that short-term abdominal resistance training in addition to diet it did not reduce abdominal subcutaneous fat thickness compared to diet alone in overweight or obese women.
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31. Avila JJ, Gutierres JA, Sheehy ME, Lofgren IE, Delmonico MJ. Effect of moderate intensity resistance training during weight loss on body composition and physical performance in overweight older adults. Eur J Appl Physiol 2010;109(3):517-25. 32. Joseph LJ, Trappe TA, Farrell PA, et al. Short-term moderate weight loss and resistance training do not affect insulinstimulated glucose disposal in postmenopausal women. Diabetes Care 2001;24(11):1863-9. 33. Birrer RB, O'Connor FG. Sports Medicine for the Primary Care Physician. 3rd ed. Boca Raton, LA: Taylor and Francis; 2004. 34. Nakata Y, Ohkawara K, Lee DJ, Okura T, Tanaka K. Effects of additional resistance training during diet-induced weight
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loss on bone mineral density in overweight premenopausal women. J Bone Miner Metab 2008;26(2):172-7. 35. Castaneda C, Layne JE, Munoz-Orians L, et al. A randomized controlled trial of resistance exercise training to improve glycemic control in older adults with type 2 diabetes. Diabetes Care 2002;25(12):2335-41. 36. Campbell WW, Haub MD, Wolfe RR, et al. Resistance training preserves fat-free mass without impacting changes in protein metabolism after weight loss in older women. Obesity (Silver Spring) 2009;17(7):1332-9. 37. Hunter GR, Byrne NM, Sirikul B, et al. Resistance training conserves fat-free mass and resting energy expenditure following weight loss. Obesity (Silver Spring) 2008;16(5):1045-51.
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