Eating Behaviors 19 (2015) 33–38
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Eating Behaviors
Dietary adherence and acceptability of five different diets, including vegan and vegetarian diets, for weight loss: The New DIETs study Wendy J. Moore a,1, Michael E. McGrievy b,2, Gabrielle M. Turner-McGrievy c,⁎ a b c
University of South Carolina, Arnold School of Public Health, Health Promotion, Education, and Behavior, Discovery I, 915 Greene Street, Room 535, Columbia, SC 29208, United States University of Akron, Department of Statistics, 302 East Buchtel Avenue, Akron, OH 44325, United States University of South Carolina, Arnold School of Public Health, Health Promotion, Education, and Behavior, Discovery I, 915 Greene Street, Room 529, Columbia, SC 29208, United States
a r t i c l e
i n f o
Article history: Received 6 March 2015 Received in revised form 12 May 2015 Accepted 24 June 2015 Available online 2 July 2015 Keywords: Vegan Vegetarian Adherence Acceptability Diets Weight loss
a b s t r a c t The goal of the present study was to examine dietary adherence and acceptability among participants from the New DIETs study who were randomized to one of four plant-based diets (vegan, vegetarian, pesco-vegetarian, semi-vegetarian) or an omnivore diet. Primary outcomes at two- and six months included dietary adherence (24-hour dietary recalls), weight loss and changes in animal product intake (mg cholesterol) by adherence status, Three-Factor Eating Questionnaire (TFEQ), Power of Food Scale (PFS), dietary acceptability (Food Acceptability Questionnaire), and impact of diet preference on adherence. No differences were found in dietary adherence or changes in FAQ, TFEQ, or PFS among the groups. At six months, non-adherent vegan and vegetarian participants (n = 16) had a significantly greater decrease in cholesterol intake (− 190.2 ± 199.2 mg) than nonadherent pesco-vegetarian/semi-vegetarian (n = 15, − 2.3 ± 200.3 mg, P = 0.02) or omnivore participants (n = 7, 17.0 ± 36.0, P = 0.04). Non-adherent vegan/vegetarian participants lost significantly more weight at six months (−6.0 ± 6.7%) than non-adherent omnivore participants (−0.4 ± 0.6%, P = 0.04). Dietary preference had no impact on adherence at six months. Due to equal rates of adherence and acceptability among the diet groups, instructing participants to follow vegan or vegetarian diets may have a greater impact on weight loss and animal product intake than providing instruction in more moderate approaches even among nonadherent participants. © 2015 Elsevier Ltd. All rights reserved.
1. Introduction Several factors, such as self-efficacy, outcome expectation and perceived value, and social support, can affect adherence to health promotion or dietary interventions (Shay, 2008). In addition, acceptability of the diets prescribed during the intervention may also impact adherence (Barnard et al., 2009). Eating behavior, specifically cognitive restraint (Three Factor Eating Questionnaire (TFEQ) (Stunkard & Messick, 1985)), may also have an effect on adherence levels to dietary change interventions (Barnard et al., 2009; Westerterp-Plantenga, Kempen, & Saris, 1998). Individuals who report high susceptibility for food (Power of Food Scale (PFS)) (Lowe et al., 2009), may have a more difficult time using behavioral coping strategies during a dietary intervention (Forman et al., 2007; Lowe et al., 2009). While prior studies have examined dietary adherence/acceptability between vegan diets and standard diets (Barnard, Gloede, et al., 2009; ⁎ Corresponding author. Tel.: +1 803 777 3932; fax: +1 803 777 9007. E-mail addresses: [email protected] (W.J. Moore), [email protected] (M.E. McGrievy), [email protected] (G.M. Turner-McGrievy). 1 Tel.: +1 706 455 4464; fax: +1 803 777 9007. 2 Tel.: +1 330 972 6886.
http://dx.doi.org/10.1016/j.eatbeh.2015.06.011 1471-0153/© 2015 Elsevier Ltd. All rights reserved.
N. D. Barnard, Scialli, Bertron, Hurlock, & Edmonds, 2000; Barnard, Scialli, Turner-McGrievy, & Lanou, 2004; Turner-McGrievy, Barnard, & Scialli, 2007), no studies to date have compared adherence/acceptability among groups assigned to follow a variety of plant-based diets. The present study had the following research questions: 1. What is the difference in dietary adherence/acceptability, TFEQ, and PFS scores among participants randomized to one of four plantbased diets or an omnivorous diet at two months (after an initial intensive intervention) and six months (maintenance)? a. We hypothesized that there would be no differences in dietary adherence/acceptability, TFEQ, or PFS among the five diet groups at either two- or six-months. 2. How does dietary adherence impact weight loss and changes in consumption of animal products (mg cholesterol/day) among participants assigned to meat-free, moderate meat, or unrestricted meat diets? a. We hypothesized that weight loss and animal product intake would not differ among adherent participants but that nonadherent participants assigned to a meat-free diet (vegan or vegetarian) would have greater weight loss and decreases in
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W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
animal product intake at six months compared to those assigned to diets recommending moderate levels of animal intake (pescovegetarian or semi-vegetarian) or an omnivorous diet. 3. How do baseline dietary preference and PFS score impact dietary adherence? a. We hypothesized that neither dietary preference nor dislike would be related to dietary adherence but that having higher baseline PFS scores would be associated with non-adherence to the assigned diet at six months.
have previously reported on our methods for handling missing data for body weight and dietary intake (Turner-McGrievy, Davidson, Wingard, Wilcox, & Frongillo, 2014; Turner-McGrievy, Wirth, et al., 2014). Chi-square test of independence was used to examine differences in dietary adherence, being matched for diet preference, and being matched for the diet disliked among the five groups. All analyses were conducted using SPSS 22.0 for Windows software with a p value of 0.05 used to indicate statistically significant differences (2014. Chicago: SPSS Inc.).
3. Results 2. Materials and methods The methods for conducting the New DIETs study, including description of the groups, are found in detail elsewhere (Turner-McGrievy, Davidson, Wingard, Wilcox, & Frongillo, 2014; Turner-McGrievy, et al., 2014). Overweight and obese adults (n = 63; Body Mass Index (BMI) 25–49.9 kg/m2) were randomly assigned to five different diets: Vegan, Vegetarian (veg), Pesco-vegetarian (pesco-veg), Semi-vegetarian (semi-veg), and Omnivore (omni). The dietary intervention consisted of a two-month intensive dietary intervention with a four-month maintenance phase. At each time point, participants completed two days of unannounced 24-hour dietary recalls collected using the Automated Self-administered 24-hour Dietary Recall (ASA24™) (Subar et al., 2010). In addition, participants completed the Food Acceptability Questionnaire (FAQ) (Barnard et al., 2004), TFEQ, and PFS. The TFEQ (Karlsson, Persson, Sjostrom, & Sullivan, 2000), FAQ (Barnard et al., 2000), and PFS (Cappelleri et al., 2009) have demonstrated validity in prior studies. Prior to the beginning of the study, participants also indicated which diet they wanted and did not want. Dietary adherence was measured as the absence of any proscribed foods from the dietary recalls at each time point. For the omni group, they were considered to be adherent if their energy from fat was ≤ 40%. This method of assessing dietary adherence has been used in previous studies (Barnard, Gloede, et al., 2009; Turner-McGrievy et al., 2007). Percent weight loss at six months among participants who were adherent to their diets (n = 25) and those who were nonadherent (n = 37) was examined among participants instructed to follow a meat-free diet (vegan or veg groups), a diet that allowed moderate intake of meat (pesco-veg or semi-veg), or a diet with unrestricted animal product intake (omni) at six months. 2.1. Statistical analysis One-way ANOVA with post hoc Tukey's test was used to examine changes in main variables at two months and six months among the five diets or the collapsed three diets (no meat, moderate meat, or omnivorous groups). For questionnaire outcomes, only participants who had data at each time point were included in the analyses. We
Baseline demographics and study completion rates have been presented elsewhere (Turner-McGrievy, Davidson, & Wilcox, 2014; Turner-McGrievy, Davidson, Wingard, Wilcox, & Frongillo, 2015). Participants had a mean age (± SD) of 48.5 ± 8.3 years and were mostly white (79%), college educated (98%) females (73%).
3.1. Adherence Table 1 presents the adherence rates for each group at two and six months as well as the actual diets participants were following. No differences in dietary adherence among the five groups were found at two (χ2 = 5.2, P = 0.27) or six months (χ2 = 0.47, P = 0.98). Examining non-adherent participants, vegan and veg participants (n = 16 nonadherent) had a significantly greater decrease in cholesterol intake at six months (− 190.2 ± 199.2 mg) as compared to non-adherent pesco-veg and semi-veg participants (n = 15, −2.3 ± 200.3 mg, P = 0.02) or omni participants (n = 7, 17.0 ± 36.0, P = 0.04). Examining adherent participants only, changes in cholesterol intake were not significantly different (F = 1.68; P = 0.21) among adherent vegan/ veg (n = 9, −232.0 ± 233.4), pesco-veg/semi-veg (n = 11, −81.8 ± 152.4), or omni participants (n = 5, −116.2 ± 152.3).
3.2. Weight loss One participant (vegan group) was diagnosed with insulin-resistant polycystic ovary syndrome and hypothyroidism during the first month of the study and began treatment with levothyroxine and metformin, which excluded her from weight loss analyses. Non-adherent vegan and veg participants lost significantly more weight at six months (n = 15; −6.0 ± 6.7%) compared to non-adherent omni participants (n = 7; −0.4 ± 0.6%, P = 0.04) and was approaching significance for differences between the non-adherent vegan/veg and pesco-veg/semiveg group (n = 15; −1.9 ± 3.1%, P = 0.06). There was no difference in weight loss (F = 2.78, P = 0.08) among adherent vegan and veg participants (n = 9, − 8.3 ± 3.1%), pesco-veg/semi-veg (n = 11, −5.0 ± 3.5%), or omni participants (n = 5, −6.9 ± 1.7%).
Table 1 Dietary pattern followed at each time point by each group during a six month, randomized, weight loss intervention. Randomized groups Vegan (n = 12)
Vegetarian (n = 13)
Pesco-veg (n = 13)
Semi-veg (n = 13)
Omni (n = 12)
Diet participants were following at each time point based on dietary recalls
2 mo.
6 mo.
2 mo.
6 mo.
2 mo.
6 mo.
2 mo.
6 mo.
2 mo.
6 mo.
Vegan Vegetarian Pesco-veg Semi-veg Omnivore Non-adherent No data
6 (50%) 6 (50%) 0 0 0 0 0
4 (33%) 1 (8%) 1 (8%) 2 (17%) 2 (17 %) 1 (8%) 1 (8%)
0 12 (92%) 1 (8%) 0 0 0 0
0 5 (38%) 2 (15%) 1 (8%) 2 (15%) 0 3 (24%)
0 6 (46%) 7 (54%) 0 0 0 0
0 1 (8%) 4 (31%) 4 (31%) 2 (15%) 0 2 (15%)
0 0 0 8 (62%) 0 1 (8%) 4 (30%)
0 0 0 6 (46%) 2 (15%) 1 (8%) 4 (30%)
0 0 0 3 (26%) 1 (8%) 4 (33%) 4 (33%)
0 0 0 3 (26%) 2 (17%) 2 (17%) 5 (40%)
Percentage of participants who were adherent to their diets at two and six months is bolded for each group.
W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
3.3. Dietary acceptability and other questionnaires No differences among the five groups were found for dietary adherence or changes in FAQ, TFEQ, and PFS at either two- or six months (Table 2). Regardless of diet assignment, collapsing all groups together, participants reported improvements in the appearance of their diet (P = 0.01), meal satisfaction (P = 0.002), and overall dietary satisfaction (P b 0.001) on the FAQ. For the TFEQ, participants reported increases in cognitive control (P b 0.001), decreases in disinhibition (P b 0.001), and decreases in hunger (P = 0.003). For the PFS, participants improved scores for food availability and food present (P b 0.001), food tasted (P = 0.005), and total change (P b 0.001). 3.4. Factors impacting dietary adherence For preference and dislike, 54% (n = 34) of participants were assigned the diet they preferred and 40% (n = 25) of participants were assigned to a diet they did not prefer. More people in the omni (n = 6, 50% of omni group) and vegan groups (n = 8; 73% of vegan) were assigned the diet they disliked as compared to the other groups (χ2 = 14.02, P = 0.01). There was no difference among the groups for being assigned to their preferred diet (χ2 = 2.27, P = 0.69). Dietary adherence at six months did not differ between those who received their preferred diet and those who did not (χ2 = 0.20; P = 0.66) or between those who received their disliked diet and those who did not (χ2 = 0.02; P = 0.90). Also, counter to our hypothesis that having higher baseline PFS scores would be associated with reduced dietary adherence, none of the domains of the PFS (food tasted, P = 0.94; food present, P = 0.37; food available, P = 0.56) were associated with adherence at six months. 4. Discussion The present study examined dietary adherence and acceptability, as well as other food-related domains, such as dietary restraint, hunger, and the power of food. There were no significant differences among the five groups in dietary adherence or acceptability, TFEQ, or PFS, which is similar to findings of other studies examining adherence and acceptability of plant-based diets (Barnard, Gloede, et al., 2009; Barnard et al., 2000; Barnard et al., 2004; Berkow, Barnard, Eckart, & Katcher, 2010). The present study also did not find any baseline factors that were predictive of dietary adherence, such as dietary preference or baseline PFS scores. The findings of this study suggest that counseling overweight individuals to follow plant-based approaches, such as vegan and vegetarian diets, may allow for greater weight loss and decreases in animal product intake as compared to approaches that include meat, even in the absence of 100% adherence to the diets. While dietary adherence and acceptability are often thought of as important factors that allow plant-based approaches to be successful, the present study suggests that these factors may not need to be of critical concern. All groups had similar adherence/acceptability. Similar results were found in a review paper that examined adherence rates among participants in interventions examining vegan, vegetarian, and omnivorous diets lasting more than a year, with adherence rates ranging from 51% to 61% for vegan and vegetarian diets and 20% to 55% for omnivorous diets, with no differences in acceptability across diets (Berkow et al., 2010). Despite the low adherence rates among participants, non-adherent vegan and vegetarian participants still had diets that contained fewer animal products than non-adherent pesco-vegetarian or semivegetarian participants and omnivorous participants. Non-adherent vegan and vegetarian participants also experienced greater weight loss than non-adherent omni participants. Even if it is expected that participants will not be completely adherent to plant-based approaches, instructing participants to following diets that are often viewed as more
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extreme (Cole, 2008) could be a way to promote more plant-based dietary eating patterns and weight loss. Improvements in TEFQ scores were observed for the group as a whole and similar to other studies where restraint scores increased (Barnard, Cohen, et al., 2009; Westerterp-Plantenga et al., 1998) and disinhibition and hunger scores decreased (Barnard, Cohen, et al., 2009). Examining the PFS, the group as a whole reported becoming more capable of resisting foods in their immediate environment that violated their assigned diet, avoiding foods that are present and available but not allowed by their assigned diet, and avoiding further consumption of foods that violated their assigned diet even after it was tasted. Contrary to what other studies have found (Forman et al., 2007; Lowe, 2003), the present study did not find having higher baseline PFS score to be associated with reduced dietary adherence. While dietary preference has demonstrated to have an impact on adherence and weight loss (Mendonca & Brehm, 1983), the present study, as well as others (Burke et al., 2008) have found no impact of baseline dietary preference and treatment outcomes. One study found that participants who were not assigned to their preferred diet were more successful than those who had the diet they preferred (Burke et al., 2008). Participant willingness to succeed and/or the fact that participants simply forgot their preference over the duration of the trial were attributed to explaining the findings (Burke et al., 2008). The present study has several strengths. It is one of the first randomized, controlled trials to examine adherence, acceptability, and other diet-related factors among four different plant-based diets plus an omnivorous diet. The study also used validated measures to assess dietrelated behaviors and dietary intake, which was collected by two unannounced, 24-hr recalls and is considered to be an accurate way to measure overall dietary intake (Field et al., 1998; Kristal, Peters, & Potter, 2005; Lagerros et al., 2006). There are also limitations, including the short duration and a small sample that was mostly White and educated. In addition, neither participants nor study personnel were blinded to diet assignment. Future studies should examine longer-term dietary adherence and acceptability, beyond the six-month time frame. 5. Conclusions In conclusion, low dietary adherence and acceptability are often thought of as a concern over using more plant-based diets for weight loss and other health outcomes as demonstrated by the US News and World Report 2015 Best Diets Ranking report, which said of the Ornish diet (a primarily vegan diet) that “most people have trouble sticking to restrictive diets” (U.S.News&WorldReport (Producer)., 2015). The present study found similar dietary adherence/acceptability across five different diets. Because non-adherent individuals randomized into meatfree diets (vegan or vegetarian groups) still had greater decreases in animal product intake (dietary cholesterol intake) and weight loss compared to their counterparts who were assigned to groups that allowed meat (pesco-veg/semi-vegetarian and omnivorous groups), and dietary adherence/acceptability are similar across groups, instructing participants to follow plant-based approaches for weight loss may have greater benefits than providing instruction in approaches that contain meat. Role of funding sources Funding for this study was provided by internal start-up funds to the Principal Investigator. The funders had no role in the study design, collection, analysis or interpretation of the data, writing the manuscript, or the decision to submit the paper for publication.
Contributors GTM designed the study and wrote the protocol. MEM conducted the statistical analysis. WJM wrote the first draft of the manuscript and all authors contributed to and have approved the final manuscript.
Conflict of interest All authors declare that they have no conflicts of interest.
36 Table 2 Baseline scores and differences from baseline to two- and six-months for the Food Acceptability Questionnaire (FAQ), Three Factor Eating Questionnaire (TFEQ), and Power of Food Scale (PFS) for each group during a six month, randomized, weight loss intervention. Vegetarian
Pesco-vegetarian
Semi-vegetarian
Omnivorous
P-value for difference among groups
12
13
13
13
12
5.83 ± 0.24 −0.42 ± 0.23 0.09 ± 0.29
5.69 ± 0.21 −0.31 ± 0.38 0.20 ± 0.3
5.58 ± 0.38 0.00 ± 0.49 0.25 ± 0.59
5.00 ± 0.41 0.86 ± 0.60 1.14 ± 0.53
5.17 ± 0.37 0.44 ± 0.34 0.14 ± 0.55
P = 0.33 P = 0.23 P = 0.52
5.75 ± 0.22 −0.25 ± 0.22 0.00 ± 0.20
5.77 ± 0.23 −0.54 ± 0.43 0.00 ± 0.30
5.75 ± 0.37 −0.25 ± 0.41 0.25 ± 0.59
5.08 ± 0.43 0.71 ± 0.64 0.71 ± 0.52
5.00 ± 0.37 0.67 ± 0.37 0.29 ± 0.42
P = 0.25 P = 0.15 P = 0.75
5.50 ± 0.26 0.00 ± 0.39 0.36 ± 0.36
5.08 ± 0.28 0.15 ± 0.48 0.70 ± 0.34
5.25 ± 0.33 0.33 ± 0.41 0.63 ± 0.71
4.75 ± 0.37 0.86 ± 0.51 1.14 ± 0.55
5.00 ± 0.37 0.22 ± 0.43 0.29 ± 0.84
P = 0.58 P = 0.80 P = 0.84
2.67 ± 0.36 1.33 ± 0.56 −0.18 ± 0.46
3.31 ± 0.31 −0.46 ± 0.45 0.00 ± 0.65
3.58 ± 0.45 0.25 ± 0.71 −0.13 ± 0.94
3.92 ± 0.40 −0.86 ± 0.74 −0.86 ± 0.91
4.18 ± 0.66 −0.75 ± 1.03 −1.14 ± 1.28
P = 0.15 P = 0.14 P = 0.83
5.50 ± 0.38 −0.08 ± 0.40 0.00 ± 0.47
5.00 ± 0.34 0.54 ± 0.27 0.80 ± 0.63
5.58 ± 0.34 −0.25 ± 0.48 0.13 ± 0.40
4.45 ± 0.64 −1.00 ± 0.85 −0.71 ± 0.61
5.00 ± 0.37 0.00 ± 0.80 −0.71 ± 0.75
P = 0.35 P = 0.43 P = 0.32
5.83 ± 0.37 −0.67 ± 0.43 −0.60 ± 0.52
5.85 ± 0.27 −0.92 ± 0.51 −0.60 ± 0.52
5.92 ± 0.26 0.08 ± 0.38 0.38 ± 0.57
5.42 ± 0.34 −0.43 ± 0.65 −0.29 ± 0.75
5.58 ± 0.36 0.11 ± 0.46 −0.57 ± 0.72
P = 0.79 P = 0.43 P = 0.75
4.17 ± 0.67 −0.42 ± 0.73 −0.81 ± 0.90
4.23 ± 0.53 1.23 ± 0.76 0.90 ± 0.86
4.58 ± 0.34 1.00 ± 0.56 0.00 ± 0.63
3.42 ± 0.58 1.43 ± 0.78 0.86 ± 1.06
4.00 ± 0.67 −1.22 ± 0.74 −0.86 ± 0.63
P = 0.70 P = 0.07 P = 0.60
5.58 ± 0.47 −1.25 ± 0.75 −1.09 ± 0.53
3.85 ± 0.49 0.92 ± 0.79 0.60 ± 0.82
4.42 ± 0.54 0.58 ± 0.40 0.25 ± 0.70
4.42 ± 0.57 −0.71 ± 0.97 −1.57 ± 0.90
3.58 ± 0.67 −0.11 ± 0.70 −0.14 ± 1.08
P = 0.12 P = 0.17 P = 0.27
W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
Randomized to each group (n) Food Acceptability Questionnaire How well do you like these foods? (1 not at all, 7 extremely) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How well do you like the taste of these foods? (1 not at all, 7 extremely) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How appealing or unappealing do you find the appearance of these foods? (1 extremely unappealing, 7 extremely appealing) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How boring are these foods? (1 not at all, 7 extremely) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How easy or difficult has it been for you to prepare these foods? (1 extremely difficult, 7 extremely easy) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How easy or difficult has it been for you to purchase these foods? (1 extremely difficult, 7 extremely easy) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How easy or difficult has it been for you to maintain your current diet at restaurants? (1 extremely difficult, 7 extremely easy) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How much effort does it take for you to stay on this diet? (1 more effort than is possible, 7 no effort at all) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months
Vegan
4.83 ± 0.30 0.83 ± 0.39 0.46 ± 0.49
4.54 ± 0.37 1.42 ± 0.51 0.50 ± 0.62
4.17 ± 0.41 1.75 ± 0.54 1.63 ± 0.75
4.45 ± 0.37 1.29 ± 0.92 1.67 ± 0.49
4.73 ± 0.60 0.78 ± 0.52 0.50 ± 0.43
P = 0.81 P = 0.67 P = 0.39
3.83 ± 0.41 2.08 ± 0.53 2.273 ± 0.45
3.31 ± 0.26 2.46 ± 0.40 2.60 ± 0.43
3.08 ± 0.34 3.08 ± 0.50 2.25 ± 0.75
3.55 ± 0.41 2.43 ± 0.78 2.50 ± 0.56
3.64 ± 0.62 1.67 ± 0.82 1.67 ± 0.79
P = 0.73 P = 0.51 P = 0.54
9.67 ± 1.28 22.50 ± 1.71 3.82 ± 1.27
9.23 ± 1.07 20.00 ± 1.09 4.80 ± 1.43
9.38 ± 0.84 22.69 ± 0.80 3.78 ± 1.06
8.23 ± 0.74 17.00 ± 2.73 3.22 ± 1.14
9.25 ± 0.75 18.00 ± 2.53 4.00 ± 1.07
P = 0.86 P = 0.10 P = 0.93
8.25 ± 0.89 2.00 ± 1.13 −3.00 ± 0.94
6.77 ± 0.87 2.77 ± 0.84 −2.80 ± 1.04
8.08 ± 0.54 1.23 ± 0.86 −3.44 ± 0.77
9.08 ± 0.89 2.11 ± 1.90 −1.67 ± 0.85
9.25 ± 0.89 2.50 ± 1.11 −2.71 ± 1.54
P = 0.56 P = 0.88 P = 0.80
5.75 ± 1.18 4.92 ± 1.12 −1.55 ± 0.98
5.31 ± 0.89 6.62 ± 0.68 −1.50 ± 0.76
5.31 ± 1.01 6.69 ± 0.97 −1.89 ± 0.92
5.92 ± 0.82 4.78 ± 2.34 −0.89 ± 1.05
5.17 ± 1.00 6.40 ± 1.35 0.00 ± 0.66
P = 0.98 P = 0.67 P = 0.69
23.67 ± 2.29 29.42 ± 1.40 −0.73 ± 1.00
24.31 ± 1.96 29.39 ± 1.39 0.50 ± 1.78
22.77 ± 1.35 30.62 ± 1.45 −1.56 ± 1.49
23.23 ± 1.23 23.89 ± 6.10 0.67 ± 2.22
23.67 ± 1.64 26.90 ± 3.78 1.29 ± 1.55
P = 0.98 P = 0.54 P = 0.76
13.50 ± 2.12 −3.83 ± 1.58 −4.00 ± 1.56
13.23 ± 1.50 −2.39 ± 0.96 −3.20 ± 1.45
12.23 ± 1.59 −3.08 ± 1.57 −.056 ± 1.16
12.39 ± 1.62 −2.00 ± 1.24 −1.13 ± 0.61
15.08 ± 1.49 −4.89 ± 2.73 −4.14 ± 2.42
P = 0.77 P = 0.79 P = 0.33
11.92 ± 1.25 −4.50 ± 1.40 −4.55 ± 1.30
11.92 ± 1.09 −3.23 ± 1.33 −4.80 ± 1.16
10.92 ± 1.17 −4.23 ± 1.05 −2.22 ± 0.78
12.00 ± 0.93 −3.00 ± 0.54 −2.63 ± 0.71
11.83 ± 0.88 −3.22 ± 1.63 −3.00 ± 2.04
P = 0.95 P = 0.89 P = 0.46
13.58 ± 1.69 −2.17 ± 1.26 −2.36 ± 0.94
12.54 ± 0.94 −0.62 ± 0.93 −1.30 ± 0.90
11.92 ± 1.02 −1.23 ± 0.96 −0.11 ± 0.99
11.39 ± 1.13 0.25 ± 0.75 −0.88 ± 0.77
13.33 ± 1.01 −1.44 ± 1.20 −2.14 ± 1.74
P = 0.65 P = 0.63 P = 0.54
39.00 ± 4.68 −10.50 ± 4.03 −10.91 ± 3.22
37.69 ± 3.10 −6.23 ± 2.77 −9.30 ± 3.23
35.08 ± 3.56 −8.54 ± 3.14 −2.89 ± 2.16
35.77 ± 3.40 −4.75 ± 1.90 −4.63 ± 1.48
40.25 ± 2.92 −9.56 ± 5.32 −7.58 ± 5.85
P = 0.83 P = 0.81 P = 0.37
W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
How satisfied or dissatisfied do you feel after eating a meal on this diet? (1 extremely dissatisfied, 7 extremely satisfied) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Overall, how satisfied or dissatisfied are you with the diet? (1 extremely dissatisfied, 7 extremely satisfied) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months TFEQ: Restraint, Disinhibition, and Hunger Dietary Restraint (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Disinhibition (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Hunger (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Eating Inventory, Total Score (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months PFS Score Power of Food Scale, Food Available: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Power of Food Scale, Food Present: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Power of Food Scale, Food Tasted: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Power of Food Scale, Total Score: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months
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Lagerros, Y. T., Mucci, L. A., Bellocco, R., Nyren, O., Balter, O., & Balter, K. A. (2006). Validity and reliability of self-reported total energy expenditure using a novel instrument. European Journal of Epidemiology, 21(3), 227–236. http://dx.doi.org/10.1007/ s10654-006-0013-y. Lowe, M. R. (2003). Self-regulation of energy intake in the prevention and treatment of obesity: Is it feasible? Obesity Research, 11(Suppl.), 44S–59S. http://dx.doi.org/10. 1038/oby.2003.223. Lowe, M. R., Butryn, M. L., Didie, E. R., Annunziato, R. A., Thomas, J. G., Crerand, C. E., & Halford, J. (2009). The Power of Food Scale. A new measure of the psychological influence of the food environment. Appetite, 53(1), 114–118. http://dx.doi.org/10. 1016/j.appet.2009.05.016. Mendonca, P. J., & Brehm, S. S. (1983). Effects of choice on behavioral treatment of overweight children. Journal of Social and Clinical Psychology, 1(4), 343–358. Shay, L. E. (2008). A concept analysis: Adherence and weight loss. Nursing Forum, 43(1), 42–52. http://dx.doi.org/10.1111/j.1744-6198.2008.00095.x. Stunkard, A. J., & Messick, S. (1985). The three-factor eating questionnaire to measure dietary restraint, disinhibition and hunger. Journal of Psychosomatic Research, 29(1), 71–83. Subar, A. F., Crafts, J., Zimmerman, T. P., Wilson, M., Mittl, B., Islam, N. G., & Thompson, F. E. (2010). Assessment of the accuracy of portion size reports using computer-based food photographs aids in the development of an automated self-administered 24-hour recall. Journal of the American Dietetic Association, 110(1), 55–64 doi: S0002-8223(09)01683-6 [pii] 10.1016/j.jada.2009.10.007. Turner-McGrievy, G. M., Barnard, N. D., & Scialli, A. R. (2007). A two-year randomized weight loss trial comparing a vegan diet to a more moderate low-fat diet. Obesity (Silver Spring), 15(9), 2276–2281 doi: 15/9/2276 [pii] 10.1038/oby.2007.270. Turner-McGrievy, G. M., Davidson, C. R., & Wilcox, S. (2014). Does the type of weight loss diet affect who participates in a behavioral weight loss intervention? A comparison of participants for a plant-based diet versus a standard diet trial. Appetite, 73, 156–162. http://dx.doi.org/10.1016/j.appet.2013.11.008. Turner-McGrievy, G. M., Davidson, C. R., Wingard, E. E., Wilcox, S., & Frongillo, E. A. (2015). Comparative effectiveness of plant-based diets for weight loss: A randomized controlled trial of five different diets. Nutrition, 31(2), 350–358. http://dx.doi.org/10. 1016/j.nut.2014.09.002. Turner-McGrievy, G. M., Wirth, M. D., Shivappa, N., Wingard, E. E., Fayad, R., Wilcox, S., & Hébert, J. R. (2014). Randomization to plant-based dietary approaches leads to larger short-term improvements in Dietary Inflammatory Index scores and macronutrient intake compared with diets that contain meat. Nutrition Research (New York), 35(2), 97–106. http://dx.doi.org/10.1016/j.nutres.2014.11.007. U.S.News&WorldReport (Producer). (2015). Easiest diets to follow. U.S. News & World Report Health. Retrieved from http://health.usnews.com/best-diet/best-easy-diets? page=3. Westerterp-Plantenga, M. S., Kempen, K. P., & Saris, W. H. (1998). Determinants of weight maintenance in women after diet-induced weight reduction. International Journal of Obesity and Related Metabolic Disorders, 22(1), 1–6.
Contents lists available at ScienceDirect
Eating Behaviors
Dietary adherence and acceptability of five different diets, including vegan and vegetarian diets, for weight loss: The New DIETs study Wendy J. Moore a,1, Michael E. McGrievy b,2, Gabrielle M. Turner-McGrievy c,⁎ a b c
University of South Carolina, Arnold School of Public Health, Health Promotion, Education, and Behavior, Discovery I, 915 Greene Street, Room 535, Columbia, SC 29208, United States University of Akron, Department of Statistics, 302 East Buchtel Avenue, Akron, OH 44325, United States University of South Carolina, Arnold School of Public Health, Health Promotion, Education, and Behavior, Discovery I, 915 Greene Street, Room 529, Columbia, SC 29208, United States
a r t i c l e
i n f o
Article history: Received 6 March 2015 Received in revised form 12 May 2015 Accepted 24 June 2015 Available online 2 July 2015 Keywords: Vegan Vegetarian Adherence Acceptability Diets Weight loss
a b s t r a c t The goal of the present study was to examine dietary adherence and acceptability among participants from the New DIETs study who were randomized to one of four plant-based diets (vegan, vegetarian, pesco-vegetarian, semi-vegetarian) or an omnivore diet. Primary outcomes at two- and six months included dietary adherence (24-hour dietary recalls), weight loss and changes in animal product intake (mg cholesterol) by adherence status, Three-Factor Eating Questionnaire (TFEQ), Power of Food Scale (PFS), dietary acceptability (Food Acceptability Questionnaire), and impact of diet preference on adherence. No differences were found in dietary adherence or changes in FAQ, TFEQ, or PFS among the groups. At six months, non-adherent vegan and vegetarian participants (n = 16) had a significantly greater decrease in cholesterol intake (− 190.2 ± 199.2 mg) than nonadherent pesco-vegetarian/semi-vegetarian (n = 15, − 2.3 ± 200.3 mg, P = 0.02) or omnivore participants (n = 7, 17.0 ± 36.0, P = 0.04). Non-adherent vegan/vegetarian participants lost significantly more weight at six months (−6.0 ± 6.7%) than non-adherent omnivore participants (−0.4 ± 0.6%, P = 0.04). Dietary preference had no impact on adherence at six months. Due to equal rates of adherence and acceptability among the diet groups, instructing participants to follow vegan or vegetarian diets may have a greater impact on weight loss and animal product intake than providing instruction in more moderate approaches even among nonadherent participants. © 2015 Elsevier Ltd. All rights reserved.
1. Introduction Several factors, such as self-efficacy, outcome expectation and perceived value, and social support, can affect adherence to health promotion or dietary interventions (Shay, 2008). In addition, acceptability of the diets prescribed during the intervention may also impact adherence (Barnard et al., 2009). Eating behavior, specifically cognitive restraint (Three Factor Eating Questionnaire (TFEQ) (Stunkard & Messick, 1985)), may also have an effect on adherence levels to dietary change interventions (Barnard et al., 2009; Westerterp-Plantenga, Kempen, & Saris, 1998). Individuals who report high susceptibility for food (Power of Food Scale (PFS)) (Lowe et al., 2009), may have a more difficult time using behavioral coping strategies during a dietary intervention (Forman et al., 2007; Lowe et al., 2009). While prior studies have examined dietary adherence/acceptability between vegan diets and standard diets (Barnard, Gloede, et al., 2009; ⁎ Corresponding author. Tel.: +1 803 777 3932; fax: +1 803 777 9007. E-mail addresses: [email protected] (W.J. Moore), [email protected] (M.E. McGrievy), [email protected] (G.M. Turner-McGrievy). 1 Tel.: +1 706 455 4464; fax: +1 803 777 9007. 2 Tel.: +1 330 972 6886.
http://dx.doi.org/10.1016/j.eatbeh.2015.06.011 1471-0153/© 2015 Elsevier Ltd. All rights reserved.
N. D. Barnard, Scialli, Bertron, Hurlock, & Edmonds, 2000; Barnard, Scialli, Turner-McGrievy, & Lanou, 2004; Turner-McGrievy, Barnard, & Scialli, 2007), no studies to date have compared adherence/acceptability among groups assigned to follow a variety of plant-based diets. The present study had the following research questions: 1. What is the difference in dietary adherence/acceptability, TFEQ, and PFS scores among participants randomized to one of four plantbased diets or an omnivorous diet at two months (after an initial intensive intervention) and six months (maintenance)? a. We hypothesized that there would be no differences in dietary adherence/acceptability, TFEQ, or PFS among the five diet groups at either two- or six-months. 2. How does dietary adherence impact weight loss and changes in consumption of animal products (mg cholesterol/day) among participants assigned to meat-free, moderate meat, or unrestricted meat diets? a. We hypothesized that weight loss and animal product intake would not differ among adherent participants but that nonadherent participants assigned to a meat-free diet (vegan or vegetarian) would have greater weight loss and decreases in
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W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
animal product intake at six months compared to those assigned to diets recommending moderate levels of animal intake (pescovegetarian or semi-vegetarian) or an omnivorous diet. 3. How do baseline dietary preference and PFS score impact dietary adherence? a. We hypothesized that neither dietary preference nor dislike would be related to dietary adherence but that having higher baseline PFS scores would be associated with non-adherence to the assigned diet at six months.
have previously reported on our methods for handling missing data for body weight and dietary intake (Turner-McGrievy, Davidson, Wingard, Wilcox, & Frongillo, 2014; Turner-McGrievy, Wirth, et al., 2014). Chi-square test of independence was used to examine differences in dietary adherence, being matched for diet preference, and being matched for the diet disliked among the five groups. All analyses were conducted using SPSS 22.0 for Windows software with a p value of 0.05 used to indicate statistically significant differences (2014. Chicago: SPSS Inc.).
3. Results 2. Materials and methods The methods for conducting the New DIETs study, including description of the groups, are found in detail elsewhere (Turner-McGrievy, Davidson, Wingard, Wilcox, & Frongillo, 2014; Turner-McGrievy, et al., 2014). Overweight and obese adults (n = 63; Body Mass Index (BMI) 25–49.9 kg/m2) were randomly assigned to five different diets: Vegan, Vegetarian (veg), Pesco-vegetarian (pesco-veg), Semi-vegetarian (semi-veg), and Omnivore (omni). The dietary intervention consisted of a two-month intensive dietary intervention with a four-month maintenance phase. At each time point, participants completed two days of unannounced 24-hour dietary recalls collected using the Automated Self-administered 24-hour Dietary Recall (ASA24™) (Subar et al., 2010). In addition, participants completed the Food Acceptability Questionnaire (FAQ) (Barnard et al., 2004), TFEQ, and PFS. The TFEQ (Karlsson, Persson, Sjostrom, & Sullivan, 2000), FAQ (Barnard et al., 2000), and PFS (Cappelleri et al., 2009) have demonstrated validity in prior studies. Prior to the beginning of the study, participants also indicated which diet they wanted and did not want. Dietary adherence was measured as the absence of any proscribed foods from the dietary recalls at each time point. For the omni group, they were considered to be adherent if their energy from fat was ≤ 40%. This method of assessing dietary adherence has been used in previous studies (Barnard, Gloede, et al., 2009; Turner-McGrievy et al., 2007). Percent weight loss at six months among participants who were adherent to their diets (n = 25) and those who were nonadherent (n = 37) was examined among participants instructed to follow a meat-free diet (vegan or veg groups), a diet that allowed moderate intake of meat (pesco-veg or semi-veg), or a diet with unrestricted animal product intake (omni) at six months. 2.1. Statistical analysis One-way ANOVA with post hoc Tukey's test was used to examine changes in main variables at two months and six months among the five diets or the collapsed three diets (no meat, moderate meat, or omnivorous groups). For questionnaire outcomes, only participants who had data at each time point were included in the analyses. We
Baseline demographics and study completion rates have been presented elsewhere (Turner-McGrievy, Davidson, & Wilcox, 2014; Turner-McGrievy, Davidson, Wingard, Wilcox, & Frongillo, 2015). Participants had a mean age (± SD) of 48.5 ± 8.3 years and were mostly white (79%), college educated (98%) females (73%).
3.1. Adherence Table 1 presents the adherence rates for each group at two and six months as well as the actual diets participants were following. No differences in dietary adherence among the five groups were found at two (χ2 = 5.2, P = 0.27) or six months (χ2 = 0.47, P = 0.98). Examining non-adherent participants, vegan and veg participants (n = 16 nonadherent) had a significantly greater decrease in cholesterol intake at six months (− 190.2 ± 199.2 mg) as compared to non-adherent pesco-veg and semi-veg participants (n = 15, −2.3 ± 200.3 mg, P = 0.02) or omni participants (n = 7, 17.0 ± 36.0, P = 0.04). Examining adherent participants only, changes in cholesterol intake were not significantly different (F = 1.68; P = 0.21) among adherent vegan/ veg (n = 9, −232.0 ± 233.4), pesco-veg/semi-veg (n = 11, −81.8 ± 152.4), or omni participants (n = 5, −116.2 ± 152.3).
3.2. Weight loss One participant (vegan group) was diagnosed with insulin-resistant polycystic ovary syndrome and hypothyroidism during the first month of the study and began treatment with levothyroxine and metformin, which excluded her from weight loss analyses. Non-adherent vegan and veg participants lost significantly more weight at six months (n = 15; −6.0 ± 6.7%) compared to non-adherent omni participants (n = 7; −0.4 ± 0.6%, P = 0.04) and was approaching significance for differences between the non-adherent vegan/veg and pesco-veg/semiveg group (n = 15; −1.9 ± 3.1%, P = 0.06). There was no difference in weight loss (F = 2.78, P = 0.08) among adherent vegan and veg participants (n = 9, − 8.3 ± 3.1%), pesco-veg/semi-veg (n = 11, −5.0 ± 3.5%), or omni participants (n = 5, −6.9 ± 1.7%).
Table 1 Dietary pattern followed at each time point by each group during a six month, randomized, weight loss intervention. Randomized groups Vegan (n = 12)
Vegetarian (n = 13)
Pesco-veg (n = 13)
Semi-veg (n = 13)
Omni (n = 12)
Diet participants were following at each time point based on dietary recalls
2 mo.
6 mo.
2 mo.
6 mo.
2 mo.
6 mo.
2 mo.
6 mo.
2 mo.
6 mo.
Vegan Vegetarian Pesco-veg Semi-veg Omnivore Non-adherent No data
6 (50%) 6 (50%) 0 0 0 0 0
4 (33%) 1 (8%) 1 (8%) 2 (17%) 2 (17 %) 1 (8%) 1 (8%)
0 12 (92%) 1 (8%) 0 0 0 0
0 5 (38%) 2 (15%) 1 (8%) 2 (15%) 0 3 (24%)
0 6 (46%) 7 (54%) 0 0 0 0
0 1 (8%) 4 (31%) 4 (31%) 2 (15%) 0 2 (15%)
0 0 0 8 (62%) 0 1 (8%) 4 (30%)
0 0 0 6 (46%) 2 (15%) 1 (8%) 4 (30%)
0 0 0 3 (26%) 1 (8%) 4 (33%) 4 (33%)
0 0 0 3 (26%) 2 (17%) 2 (17%) 5 (40%)
Percentage of participants who were adherent to their diets at two and six months is bolded for each group.
W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
3.3. Dietary acceptability and other questionnaires No differences among the five groups were found for dietary adherence or changes in FAQ, TFEQ, and PFS at either two- or six months (Table 2). Regardless of diet assignment, collapsing all groups together, participants reported improvements in the appearance of their diet (P = 0.01), meal satisfaction (P = 0.002), and overall dietary satisfaction (P b 0.001) on the FAQ. For the TFEQ, participants reported increases in cognitive control (P b 0.001), decreases in disinhibition (P b 0.001), and decreases in hunger (P = 0.003). For the PFS, participants improved scores for food availability and food present (P b 0.001), food tasted (P = 0.005), and total change (P b 0.001). 3.4. Factors impacting dietary adherence For preference and dislike, 54% (n = 34) of participants were assigned the diet they preferred and 40% (n = 25) of participants were assigned to a diet they did not prefer. More people in the omni (n = 6, 50% of omni group) and vegan groups (n = 8; 73% of vegan) were assigned the diet they disliked as compared to the other groups (χ2 = 14.02, P = 0.01). There was no difference among the groups for being assigned to their preferred diet (χ2 = 2.27, P = 0.69). Dietary adherence at six months did not differ between those who received their preferred diet and those who did not (χ2 = 0.20; P = 0.66) or between those who received their disliked diet and those who did not (χ2 = 0.02; P = 0.90). Also, counter to our hypothesis that having higher baseline PFS scores would be associated with reduced dietary adherence, none of the domains of the PFS (food tasted, P = 0.94; food present, P = 0.37; food available, P = 0.56) were associated with adherence at six months. 4. Discussion The present study examined dietary adherence and acceptability, as well as other food-related domains, such as dietary restraint, hunger, and the power of food. There were no significant differences among the five groups in dietary adherence or acceptability, TFEQ, or PFS, which is similar to findings of other studies examining adherence and acceptability of plant-based diets (Barnard, Gloede, et al., 2009; Barnard et al., 2000; Barnard et al., 2004; Berkow, Barnard, Eckart, & Katcher, 2010). The present study also did not find any baseline factors that were predictive of dietary adherence, such as dietary preference or baseline PFS scores. The findings of this study suggest that counseling overweight individuals to follow plant-based approaches, such as vegan and vegetarian diets, may allow for greater weight loss and decreases in animal product intake as compared to approaches that include meat, even in the absence of 100% adherence to the diets. While dietary adherence and acceptability are often thought of as important factors that allow plant-based approaches to be successful, the present study suggests that these factors may not need to be of critical concern. All groups had similar adherence/acceptability. Similar results were found in a review paper that examined adherence rates among participants in interventions examining vegan, vegetarian, and omnivorous diets lasting more than a year, with adherence rates ranging from 51% to 61% for vegan and vegetarian diets and 20% to 55% for omnivorous diets, with no differences in acceptability across diets (Berkow et al., 2010). Despite the low adherence rates among participants, non-adherent vegan and vegetarian participants still had diets that contained fewer animal products than non-adherent pesco-vegetarian or semivegetarian participants and omnivorous participants. Non-adherent vegan and vegetarian participants also experienced greater weight loss than non-adherent omni participants. Even if it is expected that participants will not be completely adherent to plant-based approaches, instructing participants to following diets that are often viewed as more
35
extreme (Cole, 2008) could be a way to promote more plant-based dietary eating patterns and weight loss. Improvements in TEFQ scores were observed for the group as a whole and similar to other studies where restraint scores increased (Barnard, Cohen, et al., 2009; Westerterp-Plantenga et al., 1998) and disinhibition and hunger scores decreased (Barnard, Cohen, et al., 2009). Examining the PFS, the group as a whole reported becoming more capable of resisting foods in their immediate environment that violated their assigned diet, avoiding foods that are present and available but not allowed by their assigned diet, and avoiding further consumption of foods that violated their assigned diet even after it was tasted. Contrary to what other studies have found (Forman et al., 2007; Lowe, 2003), the present study did not find having higher baseline PFS score to be associated with reduced dietary adherence. While dietary preference has demonstrated to have an impact on adherence and weight loss (Mendonca & Brehm, 1983), the present study, as well as others (Burke et al., 2008) have found no impact of baseline dietary preference and treatment outcomes. One study found that participants who were not assigned to their preferred diet were more successful than those who had the diet they preferred (Burke et al., 2008). Participant willingness to succeed and/or the fact that participants simply forgot their preference over the duration of the trial were attributed to explaining the findings (Burke et al., 2008). The present study has several strengths. It is one of the first randomized, controlled trials to examine adherence, acceptability, and other diet-related factors among four different plant-based diets plus an omnivorous diet. The study also used validated measures to assess dietrelated behaviors and dietary intake, which was collected by two unannounced, 24-hr recalls and is considered to be an accurate way to measure overall dietary intake (Field et al., 1998; Kristal, Peters, & Potter, 2005; Lagerros et al., 2006). There are also limitations, including the short duration and a small sample that was mostly White and educated. In addition, neither participants nor study personnel were blinded to diet assignment. Future studies should examine longer-term dietary adherence and acceptability, beyond the six-month time frame. 5. Conclusions In conclusion, low dietary adherence and acceptability are often thought of as a concern over using more plant-based diets for weight loss and other health outcomes as demonstrated by the US News and World Report 2015 Best Diets Ranking report, which said of the Ornish diet (a primarily vegan diet) that “most people have trouble sticking to restrictive diets” (U.S.News&WorldReport (Producer)., 2015). The present study found similar dietary adherence/acceptability across five different diets. Because non-adherent individuals randomized into meatfree diets (vegan or vegetarian groups) still had greater decreases in animal product intake (dietary cholesterol intake) and weight loss compared to their counterparts who were assigned to groups that allowed meat (pesco-veg/semi-vegetarian and omnivorous groups), and dietary adherence/acceptability are similar across groups, instructing participants to follow plant-based approaches for weight loss may have greater benefits than providing instruction in approaches that contain meat. Role of funding sources Funding for this study was provided by internal start-up funds to the Principal Investigator. The funders had no role in the study design, collection, analysis or interpretation of the data, writing the manuscript, or the decision to submit the paper for publication.
Contributors GTM designed the study and wrote the protocol. MEM conducted the statistical analysis. WJM wrote the first draft of the manuscript and all authors contributed to and have approved the final manuscript.
Conflict of interest All authors declare that they have no conflicts of interest.
36 Table 2 Baseline scores and differences from baseline to two- and six-months for the Food Acceptability Questionnaire (FAQ), Three Factor Eating Questionnaire (TFEQ), and Power of Food Scale (PFS) for each group during a six month, randomized, weight loss intervention. Vegetarian
Pesco-vegetarian
Semi-vegetarian
Omnivorous
P-value for difference among groups
12
13
13
13
12
5.83 ± 0.24 −0.42 ± 0.23 0.09 ± 0.29
5.69 ± 0.21 −0.31 ± 0.38 0.20 ± 0.3
5.58 ± 0.38 0.00 ± 0.49 0.25 ± 0.59
5.00 ± 0.41 0.86 ± 0.60 1.14 ± 0.53
5.17 ± 0.37 0.44 ± 0.34 0.14 ± 0.55
P = 0.33 P = 0.23 P = 0.52
5.75 ± 0.22 −0.25 ± 0.22 0.00 ± 0.20
5.77 ± 0.23 −0.54 ± 0.43 0.00 ± 0.30
5.75 ± 0.37 −0.25 ± 0.41 0.25 ± 0.59
5.08 ± 0.43 0.71 ± 0.64 0.71 ± 0.52
5.00 ± 0.37 0.67 ± 0.37 0.29 ± 0.42
P = 0.25 P = 0.15 P = 0.75
5.50 ± 0.26 0.00 ± 0.39 0.36 ± 0.36
5.08 ± 0.28 0.15 ± 0.48 0.70 ± 0.34
5.25 ± 0.33 0.33 ± 0.41 0.63 ± 0.71
4.75 ± 0.37 0.86 ± 0.51 1.14 ± 0.55
5.00 ± 0.37 0.22 ± 0.43 0.29 ± 0.84
P = 0.58 P = 0.80 P = 0.84
2.67 ± 0.36 1.33 ± 0.56 −0.18 ± 0.46
3.31 ± 0.31 −0.46 ± 0.45 0.00 ± 0.65
3.58 ± 0.45 0.25 ± 0.71 −0.13 ± 0.94
3.92 ± 0.40 −0.86 ± 0.74 −0.86 ± 0.91
4.18 ± 0.66 −0.75 ± 1.03 −1.14 ± 1.28
P = 0.15 P = 0.14 P = 0.83
5.50 ± 0.38 −0.08 ± 0.40 0.00 ± 0.47
5.00 ± 0.34 0.54 ± 0.27 0.80 ± 0.63
5.58 ± 0.34 −0.25 ± 0.48 0.13 ± 0.40
4.45 ± 0.64 −1.00 ± 0.85 −0.71 ± 0.61
5.00 ± 0.37 0.00 ± 0.80 −0.71 ± 0.75
P = 0.35 P = 0.43 P = 0.32
5.83 ± 0.37 −0.67 ± 0.43 −0.60 ± 0.52
5.85 ± 0.27 −0.92 ± 0.51 −0.60 ± 0.52
5.92 ± 0.26 0.08 ± 0.38 0.38 ± 0.57
5.42 ± 0.34 −0.43 ± 0.65 −0.29 ± 0.75
5.58 ± 0.36 0.11 ± 0.46 −0.57 ± 0.72
P = 0.79 P = 0.43 P = 0.75
4.17 ± 0.67 −0.42 ± 0.73 −0.81 ± 0.90
4.23 ± 0.53 1.23 ± 0.76 0.90 ± 0.86
4.58 ± 0.34 1.00 ± 0.56 0.00 ± 0.63
3.42 ± 0.58 1.43 ± 0.78 0.86 ± 1.06
4.00 ± 0.67 −1.22 ± 0.74 −0.86 ± 0.63
P = 0.70 P = 0.07 P = 0.60
5.58 ± 0.47 −1.25 ± 0.75 −1.09 ± 0.53
3.85 ± 0.49 0.92 ± 0.79 0.60 ± 0.82
4.42 ± 0.54 0.58 ± 0.40 0.25 ± 0.70
4.42 ± 0.57 −0.71 ± 0.97 −1.57 ± 0.90
3.58 ± 0.67 −0.11 ± 0.70 −0.14 ± 1.08
P = 0.12 P = 0.17 P = 0.27
W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
Randomized to each group (n) Food Acceptability Questionnaire How well do you like these foods? (1 not at all, 7 extremely) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How well do you like the taste of these foods? (1 not at all, 7 extremely) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How appealing or unappealing do you find the appearance of these foods? (1 extremely unappealing, 7 extremely appealing) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How boring are these foods? (1 not at all, 7 extremely) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How easy or difficult has it been for you to prepare these foods? (1 extremely difficult, 7 extremely easy) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How easy or difficult has it been for you to purchase these foods? (1 extremely difficult, 7 extremely easy) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How easy or difficult has it been for you to maintain your current diet at restaurants? (1 extremely difficult, 7 extremely easy) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months How much effort does it take for you to stay on this diet? (1 more effort than is possible, 7 no effort at all) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months
Vegan
4.83 ± 0.30 0.83 ± 0.39 0.46 ± 0.49
4.54 ± 0.37 1.42 ± 0.51 0.50 ± 0.62
4.17 ± 0.41 1.75 ± 0.54 1.63 ± 0.75
4.45 ± 0.37 1.29 ± 0.92 1.67 ± 0.49
4.73 ± 0.60 0.78 ± 0.52 0.50 ± 0.43
P = 0.81 P = 0.67 P = 0.39
3.83 ± 0.41 2.08 ± 0.53 2.273 ± 0.45
3.31 ± 0.26 2.46 ± 0.40 2.60 ± 0.43
3.08 ± 0.34 3.08 ± 0.50 2.25 ± 0.75
3.55 ± 0.41 2.43 ± 0.78 2.50 ± 0.56
3.64 ± 0.62 1.67 ± 0.82 1.67 ± 0.79
P = 0.73 P = 0.51 P = 0.54
9.67 ± 1.28 22.50 ± 1.71 3.82 ± 1.27
9.23 ± 1.07 20.00 ± 1.09 4.80 ± 1.43
9.38 ± 0.84 22.69 ± 0.80 3.78 ± 1.06
8.23 ± 0.74 17.00 ± 2.73 3.22 ± 1.14
9.25 ± 0.75 18.00 ± 2.53 4.00 ± 1.07
P = 0.86 P = 0.10 P = 0.93
8.25 ± 0.89 2.00 ± 1.13 −3.00 ± 0.94
6.77 ± 0.87 2.77 ± 0.84 −2.80 ± 1.04
8.08 ± 0.54 1.23 ± 0.86 −3.44 ± 0.77
9.08 ± 0.89 2.11 ± 1.90 −1.67 ± 0.85
9.25 ± 0.89 2.50 ± 1.11 −2.71 ± 1.54
P = 0.56 P = 0.88 P = 0.80
5.75 ± 1.18 4.92 ± 1.12 −1.55 ± 0.98
5.31 ± 0.89 6.62 ± 0.68 −1.50 ± 0.76
5.31 ± 1.01 6.69 ± 0.97 −1.89 ± 0.92
5.92 ± 0.82 4.78 ± 2.34 −0.89 ± 1.05
5.17 ± 1.00 6.40 ± 1.35 0.00 ± 0.66
P = 0.98 P = 0.67 P = 0.69
23.67 ± 2.29 29.42 ± 1.40 −0.73 ± 1.00
24.31 ± 1.96 29.39 ± 1.39 0.50 ± 1.78
22.77 ± 1.35 30.62 ± 1.45 −1.56 ± 1.49
23.23 ± 1.23 23.89 ± 6.10 0.67 ± 2.22
23.67 ± 1.64 26.90 ± 3.78 1.29 ± 1.55
P = 0.98 P = 0.54 P = 0.76
13.50 ± 2.12 −3.83 ± 1.58 −4.00 ± 1.56
13.23 ± 1.50 −2.39 ± 0.96 −3.20 ± 1.45
12.23 ± 1.59 −3.08 ± 1.57 −.056 ± 1.16
12.39 ± 1.62 −2.00 ± 1.24 −1.13 ± 0.61
15.08 ± 1.49 −4.89 ± 2.73 −4.14 ± 2.42
P = 0.77 P = 0.79 P = 0.33
11.92 ± 1.25 −4.50 ± 1.40 −4.55 ± 1.30
11.92 ± 1.09 −3.23 ± 1.33 −4.80 ± 1.16
10.92 ± 1.17 −4.23 ± 1.05 −2.22 ± 0.78
12.00 ± 0.93 −3.00 ± 0.54 −2.63 ± 0.71
11.83 ± 0.88 −3.22 ± 1.63 −3.00 ± 2.04
P = 0.95 P = 0.89 P = 0.46
13.58 ± 1.69 −2.17 ± 1.26 −2.36 ± 0.94
12.54 ± 0.94 −0.62 ± 0.93 −1.30 ± 0.90
11.92 ± 1.02 −1.23 ± 0.96 −0.11 ± 0.99
11.39 ± 1.13 0.25 ± 0.75 −0.88 ± 0.77
13.33 ± 1.01 −1.44 ± 1.20 −2.14 ± 1.74
P = 0.65 P = 0.63 P = 0.54
39.00 ± 4.68 −10.50 ± 4.03 −10.91 ± 3.22
37.69 ± 3.10 −6.23 ± 2.77 −9.30 ± 3.23
35.08 ± 3.56 −8.54 ± 3.14 −2.89 ± 2.16
35.77 ± 3.40 −4.75 ± 1.90 −4.63 ± 1.48
40.25 ± 2.92 −9.56 ± 5.32 −7.58 ± 5.85
P = 0.83 P = 0.81 P = 0.37
W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
How satisfied or dissatisfied do you feel after eating a meal on this diet? (1 extremely dissatisfied, 7 extremely satisfied) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Overall, how satisfied or dissatisfied are you with the diet? (1 extremely dissatisfied, 7 extremely satisfied) (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months TFEQ: Restraint, Disinhibition, and Hunger Dietary Restraint (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Disinhibition (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Hunger (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Eating Inventory, Total Score (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months PFS Score Power of Food Scale, Food Available: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Power of Food Scale, Food Present: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Power of Food Scale, Food Tasted: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months Power of Food Scale, Total Score: (mean ± SE) Baseline Change from baseline to two months Change from baseline to six months
37
38
W.J. Moore et al. / Eating Behaviors 19 (2015) 33–38
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