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Relative Weight, Weight Loss Efforts and Nutrient Intakes among Health-Conscious Vegetarian, Past Vegetarian and Nonvegetarian Women Ages 18 to 50.

Food, Nutrition and Health, University of British Columbia, Vancouver, British Columbia, CANADA

Address reprint requests to: S.I. Barr, PhD, Food, Nutrition and Health, University of British Columbia, 2205 East Mall, Vancouver, British Columbia, V6T 1Z4, CANADA. E-mail: sibarr{at}interchange.ubc.ca

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Objective: To compare relative weight, weight loss efforts and nutrient intakes among similarly health-conscious vegetarian, past vegetarian and nonvegetarian premenopausal women.

Methods: Demographic data, lifestyle practices and weight loss efforts (by questionnaire), body mass index (BMI;kg/m²) and dietary intake (via multiple-pass 24-hour diet recall) were compared in a convenience sample of 90 current vegetarians, 35 past vegetarians and 68 nonvegetarians.

Results: Age (31.9 ± 8.8), educational attainment, smoking status, alcohol use, physical activity and perceived health status were similar among the three groups of women. BMI did not differ by dietary pattern and averaged 23.7 ± 4.7 for all women combined. Participants had intentionally lost 10 pounds a mean of 2.1 times, and 39% of women perceived themselves to be overweight; again, no differences were observed among dietary groups. Dietary intakes of vegetarians and current nonvegetarians were consistent with current recommendations for macronutrient composition (<30% fat, <10% saturates). Compared to current nonvegetarians, current vegetarians had lower intakes of protein, saturated fat, cholesterol, niacin, vitamins B₁₂ and D, and higher fiber and magnesium intakes. Vegetarians’ mean vitamin B₁₂ and D intakes were well below recommendations.

Conclusions: Relative weight and weight loss efforts do not differ by dietary pattern among similarly health-conscious vegetarian and nonvegetarian women. The only differences in nutrient intake with potential health implications were vitamins D and B₁₂.

Key words: body mass index, diet records, health behavior, vegetarianism, weight

Abbreviations: AI = adequate intake • ANOVA = analysis of variance • BMI = body mass index • EAR = estimated average requirement • RDA = recommended dietary allowance • TFEQ = three-factor eating questionnaire • USDA = United States Department of Agriculture

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
The prevalence of vegetarianism appears to be increasing, particularly among young women [1–4]. It is likely that many factors contribute to this trend; however, it has been suggested that vegetarianism may be related in a complex manner to weight-control efforts in some young women [5,6]. Large epidemiological studies frequently report that vegetarians are leaner and lighter than nonvegetarians [e.g., 7–13], and knowledge of this association may motivate some weight-conscious young women to adopt vegetarian diets. Vegetarians in these studies, however, also differ from control subjects in other respects (e.g., higher education, higher exercise level, more health-consciousness as reflected in a lower prevalance of smoking and alcohol use) [8,10,12,13], and these differences may partially confound the observation that body weights are lower. Thus, it is difficult to determine whether differences in body weight are associated with a vegetarian dietary pattern per se or are observed because of other differences in lifestyle practices or health-consciousness.

Similarly, vegetarian diets are reported to adhere more closely to current nutrition recommendations [14,15] that emphasize lower fat and saturated fat intakes, higher fiber intakes and increased fruit and vegetable consumption [16–19]. It is possible that these differences may also be partially modulated by vegetarians’ generally healthy lifestyles.

Accordingly, the primary objective of this study was to assess the relative weight, weight loss efforts and dietary quality of health-conscious vegetarian and nonvegetarian women. We also studied women who had followed vegetarian diets in the past, but no longer did so.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Subjects
Convenience samples of premenopausal vegetarian, past vegetarian and nonvegetarian women 18 to 50 years of age were recruited to participate in the study through notices in university and community newspapers, as well as by word-of-mouth. Separate notices were developed to target vegetarian and nonvegetarian women, for whom vegetarian status was self-defined (i.e., women described themselves as currently vegetarian, as vegetarian in the past but not at present or as never vegetarian). We did not actively recruit "health-conscious" women (i.e., the only inclusion criteria were gender, age and premenopausal status), but anticipated that volunteer bias would lead to samples of vegetarians and nonvegetarians who were interested in nutrition and health [20–22]. The study protocol was approved by the University Screening Committee for Research and Other Studies Involving Human Subjects, and all subjects provided written informed consent.

Survey Instrument
Participants completed a written instrument designed to obtain information on demographics, lifestyle practices, weight loss efforts and weight perceptions, and health perceptions. Demographic data included age, ethnicity, educational attainment and student status. The lifestyle practices assessed were smoking status (current, former or never smoker), alcohol use and physical activity (perceived activity level relative to others, amount of daily walking and frequency of activity vigorous enough to lead to sweating [23]). Habitual dietary patterns were assessed using a modified food frequency questionnaire that assessed frequency of use of various protein sources (flesh foods, dairy products, eggs, beans, legumes, nuts and seeds). Weight loss efforts were assessed using questions on the number of times that 10 pounds or more had been lost (other than in association with illness or after childbirth) and on whether respondents perceived themselves to be overweight, about right or underweight. The instrument also contained the cognitive dietary restraint scale from the Three-Factor Eating questionnaire (TFEQ) [24]. This subscale assesses conscious efforts to limit food intake in an effort to control body weight. Possible scores range from 0 to 21, with higher scores reflecting higher restraint. Finally, health perceptions were assessed using a global question from Canada’s Health Promotion Survey [25] and the Mini-Duke 10-Item Health Profile scale [26]. The latter, for which possible scores range from 0 (very poor health) to 1.0 (excellent health), has been shown to correlate with days ill and physician visits in a sample of young women [26]. Before it was administered, the instrument was pilot-tested with both vegetarian and nonvegetarian women.

24-Hour Diet Recall
A trained interviewer conducted a multiple-pass 24-hour recall [27] of the previous day’s food and beverage intake. Interviews were conducted throughout a calendar year on Mondays through Fridays, reflecting intakes on Sundays through Thursdays. Three-dimensional food models were used to clarify portion size.

Height and Weight
Height (without shoes) was measured at full inspiration using a stadiometer. Weight in light indoor clothing was measured using a digital scale accurate to 0.5 kg. Measurements were done in duplicate, and, if they differed by 0.1 cm or 0.5 kg respectively, a third measurement was done and the two closest values averaged. Body mass index (BMI) was calculated as wt (kg)/ht (m²).

Data Analysis
Food intake data were analyzed using the Food Processor Plus program (Version 7.1, 1998, ESHA Research, Salem OR). The program contains a database derived from the Canadian Nutrient File as well as a large database derived from the United States Department of Agriculture (USDA) and commercial food products. Additional food and beverage items were added to the database as necessary, using information obtained from manufacturers. The USDA-derived nutrient database was used for this study, except for red meats, cereal products, milk and margarine. For these items, Canadian values were more appropriate due to differences between Canada and the U.S. in the composition of cuts of meat and in fortification practices for cereals, milk and margarine. Each entry was examined to ensure that there were no missing values for the nutrients analyzed. If nutrient information was incomplete, a food item with complete information was used (e.g., if some nutrient values were missing for a particular brand of tomato sauce, a generic tomato sauce with similar macronutrient composition and complete nutrient data was substituted).

Statistical analysis of the data was conducted using programs available in the Statistical Package for the Social Sciences (SPSS Inc., Version 8.0, 1998, Chicago IL). Data were entered and verified against original instruments. For continuous variables, differences among vegetarians, past vegetarians and nonvegetarians were examined using one-way analysis of variance (ANOVA) with post-hoc comparisons conducted with Scheffe’s test. Chi-square was calculated to test for differences in categorical variables. For comparisons between vegetarians and current nonvegetarians (past and never vegetarians combined), unpaired Student’s t tests were done. Analyses were conducted at a significance level of p<0.05, and all comparisons were two-tailed.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
Subjects
The study protocol was completed by 193 women, including 90 vegetarians, 35 past vegetarians and 68 nonvegetarians. Vegetarians had followed a vegetarian diet for almost 10 years (mean 9.7 ± 7.6, range 0.5 to 42 years). Results of the food frequency questionnaire indicated that most women who classified themselves as vegetarian excluded red meat: 95% "never" ate it, and none consumed it weekly or more often. Chicken was "never" eaten by 87% and consumed weekly by 5%, while fish was "never" eaten by 62% and eaten weekly by 12%. Past vegetarians had followed a vegetarian diet for a mean of 3.3 ± 3.6 years (range 0.1 to 13.0 years) and had resumed an omnivorous diet a mean of 7 years previously (range 0.1 to 22.5 years). Past vegetarians’ use of flesh foods (meat, poultry, fish) did not differ from nonvegetarians’ (data not shown).

Participants’ demographic characteristics are presented in Table 1. No group differences were observed in mean age, which averaged 32 years, nor in educational attainment (about 50% had completed a university degree and about 40% were current students). However, vegetarian women were significantly more likely to be Caucasian, and were less likely to have children living with them in the home.

Health Perceptions
The proportions of women who considered their health status to be "excellent," "very good," "good," "fair" and "poor" did not differ by dietary pattern and averaged 19.4%, 41.4%, 31.9%, 6.3% and 1.0%, respectively. Scores on the Mini-Duke Health Profile averaged 0.67 ± 0.11 for vegetarians, 0.61 ± 0.13 for past vegetarians and 0.64 ± 0.12 for nonvegetarians. Although vegetarians’ scores were slightly higher, the difference among groups was not significant when analyzed by ANOVA (F = 2.69, p = 0.07), nor did scores of vegetarians and nonvegetarians differ when these two groups were compared by independent sample t test (p = 0.13).

Nutrient Intakes
Initially, mean nutrient intakes were compared among vegetarians, past vegetarians and nonvegetarians using ANOVA and Scheffe’s test. However, because intakes of past vegetarians and nonvegetarians did not differ significantly for any nutrient, the data of these two groups were combined.

Table 4 displays data on energy, macronutrient, fiber and cholesterol intakes of the women. Energy intakes of vegetarians and current nonvegetarians were similar. Vegetarians had lower protein intakes in absolute terms and as a percentage of energy, and, although gram intakes of carbohydrate did not differ, vegetarians had a higher percentage of energy from carbohydrate. They also had a higher mean fiber intake. Fat intakes of the two groups did not differ, but vegetarians had significantly lower saturated fat and cholesterol intakes than nonvegetarians did.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

It was our intent to recruit groups of vegetarian and nonvegetarian women with similar lifestyle practices and with a similar degree of "health-consciousness." We did not match vegetarian and nonvegetarian subjects for these variables; instead, we simply recruited women to take part in a nutrition study and speculated that "volunteer bias" would lead to similarly health-conscious samples [20–22]. This recruitment method had both advantages and limitations. The primary advantage was, if the recruitment strategy was successful, that lifestyle practices or health-consciousness would not confound comparisons based on dietary pattern (vegetarian versus nonvegetarian). This method differs from other studies in which vegetarian subjects have recruited nonvegetarian friends to serve as the comparison group [13,16]. It could be speculated that controls selected in this manner might have had less interest in nutrition and health than their vegetarian counterparts who volunteered for the study, thus potentially biasing the results. The major limitation of our recruitment method is that the results cannot be broadly generalized to either vegetarian or nonvegetarian women. Other limitations include the small sample size and the use of self-report data. However, it should be noted that most studies of this nature rely on self-report data (thus, comparisons to other reports may be appropriate) and that reported values for height, weight and BMI in our study were directly measured.

At least as assessed by the variables monitored, we were successful in recruiting vegetarians and nonvegetarians with similar lifestyle practices. No differences by dietary pattern were observed in smoking behavior, alcohol use, physical activity, self-rated health status, age or educational attainment. The participants, however, were not representative of the general population, and thus results are limited to well educated, health-conscious women. For example, 50% had obtained a university degree, compared to 23% of Canadian women 20 to 45 years of age [29]. Fewer than 5% of participants currently smoked, while national data indicate that approximately 31% of women in this age range smoke [29]. Only 4% of the women in our study reported drinking alcohol on a daily basis, compared to about 11% of women in a national survey [29]. Physical activity levels cannot be directly compared to Canadian national data because different questions were used, but 17% to 22% of Canadian women in this age range are active in their leisure time, 22% to 26% are moderately active and 52% to 61% are inactive [29]. In our study, 46% of women perceived that they were more active than others of their age, and 49% reported walking for >30 minutes/day. Seventy-one percent reported participating in sports or vigorous physical activity "long enough to get sweaty" once or more per week; this compares to 56% of American women in this age range [30]. Taken together, these data suggest that the women who took part in this study were more physically active than were most women of their age.

A consequence of the similar lifestyle practices of the women studied is that if differences in body weight status, weight perceptions or dieting practices were detected, they could be more closely tied to dietary pattern. However, no differences in these variables were observed. Thus, in contrast to findings of epidemiological studies, among this group of women vegetarianism was not associated with a significantly greater degree of leanness or with fewer attempts to lose weight. Conversely, it was also not associated with dieting behavior or disturbed eating attitudes (as assessed by dietary restraint scores), as has been found in some studies [5,6,31], in which the degree of health-consciousness may have differed between groups. For example, it has been suggested that a vegetarian eating style may mask concerns about body weight in individuals who perceive that dieting is not socially acceptable [6]. Women with strong feminist beliefs may be such a group, as dieting is not consistent with feminist beliefs maintaining that bodies of all sizes can be attractive. In a snowball sample of 158 women, Martins et al. [6] found that weight-concerned women (assessed by high dietary restraint scores) with strong feminist values were much more likely to be vegetarian than were weight-concerned women with lower scores for feminist values. Unfortunately, their study did not obtain data on body weight or dieting practices, nor were mean values for restraint compared between vegetarians and nonvegetarians. In our study, we found restraint scores, perceptions of weight status and dieting to lose weight were similar between dietary groups. If the vegetarians we studied had higher feminist values in relation to weight than the nonvegetarians, one would anticipate that more vegetarians would have self-assessed their weight as being "about right" and fewer would have admitted to dieting for weight loss. This did not occur; accordingly, although we did not assess feminist beliefs of our participants, the results suggest that feminist beliefs as they pertain to body weight may have been similar between groups.

Vegetarian and nonvegetarian women were also compared with regard to mean nutrient intakes. Although some differences were observed between groups, what was more striking was that the macronutrient composition of both groups’ diets was consistent with current nutrition recommendations. For example, mean fat intakes were below 30% of energy and did not differ between groups (26.2% and 27.5% in vegetarians and nonvegetarians, respectively). Although vegetarians had significantly lower intakes of saturated fat in absolute terms, the percentage of energy derived from saturates did not differ (7.6% versus 8.6% of energy) and was below 10% in both groups. Cholesterol intakes were significantly lower among vegetarians, but were below 200 mg/day in both diet groups. Finally, dietary fiber intakes were higher among vegetarians, but intakes of both groups were within the recommended range of 20–35 g/day or 10–13 g/1000 kcal [32–34] and were well above mean intakes of U.S. women in the same age range [30].

Vitamin and mineral intakes were somewhat more variable, both with respect to the extent to which mean intakes approximated recommendations and with respect to differences between groups. Nutrients that may have been of concern in both groups were calcium, for which mean intakes were below the Adequate Intake (AI) [35], and zinc, for which mean intakes approximated the 1990 Canadian Recommended Nutrient Intake [14] and were less than the 1989 Recommended Dietary Allowance (RDA) [36]. Group differences were detected in the intakes of magnesium, niacin, vitamin B₁₂ and vitamin D. The differences in magnesium intake (significantly higher in vegetarians) and niacin intake (significantly higher in nonvegetarians) are likely of little physiological significance: mean magnesium intakes of both groups exceeded the RDA [35], and mean niacin intakes, even in vegetarians, were almost double the RDA [37].

The difference in vitamin B₁₂ intake is likely of greater concern. The mean vitamin B₁₂ intake of vegetarians was below the Estimated Average Requirement (EAR) of 2.0 µg for women in this age group [37]. Although inferences about nutrient adequacy of these women must be made with caution, when median intake is at the EAR, approximately 50% of individuals in a group will have inadequate intakes [37]. Our data do not include contributions from dietary supplements, which would improved intakes of some of these women. However, more than half of our participants did not use any vitamin B₁₂ containing supplements (data not shown).

The difference in vitamin D intake may also be of concern. Mean vitamin D intakes of vegetarians were only about 50% of the current AI for adult women of 200 IU [35] and were also somewhat low among nonvegetarians, although less dramatically (intake averaged almost 90% of the AI). Because of the uncertain contribution of ultraviolet irradiation, particularly at northern latitudes, dietary sources of vitamin D are recommended for maintenance of bone health [35]. Circulating levels of 25[OH]D, the transport form of the vitamin, are lower in strict vegetarians [38].

	CONCLUSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSION REFERENCES

 
We found that among health-conscious women, consuming a vegetarian diet was not associated with differences in weight status, weight perceptions or weight loss efforts. Overall, diets of both groups were generally sound, adhering to current recommendations for macronutrient distribution. Only the intakes of vitamin B₁₂ and vitamin D appeared to be of specific concern in vegetarian diets and should be addressed by supplementation if dietary sources are not adequate.

	ACKNOWLEDGMENTS

 
We greatly appreciate the assistance of Nicole Mireau and Vanessa Lam, who volunteered their time to help with locating nutrient information for foods not available in the database and with coding and verification of data. We thank Dr. Gwen Chapman and Dr. Ryna Levy-Milne for providing comments on an earlier version of this manuscript. Finally, special thanks are due to the women who took part in this study for their time, interest and enthusiasm.

This research was supported by a peer-reviewed, unrestricted research grant from the Beef Information Centre with funds obtained from the Beef Industry Development Fund, a federal/provincial initiative.

Received May 8, 2000. Accepted October 1, 2000.

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