AJM theme issue: Obesity and diabetes
Clinical research study
The effects of a low-fat, plant-based dietary intervention on body weight, metabolism, and insulin sensitivity

https://doi.org/10.1016/j.amjmed.2005.03.039Get rights and content

Abstract

Purpose

This study investigated the effect of a low-fat, plant-based diet on body weight, metabolism, and insulin sensitivity, while controlling for exercise in free-living individuals.

Subjects and methods

In an outpatient setting, 64 overweight, postmenopausal women were randomly assigned to a low-fat, vegan diet or a control diet based on National Cholesterol Education Program guidelines, without energy intake limits, and were asked to maintain exercise unchanged. Dietary intake, body weight and composition, resting metabolic rate, thermic effect of food, and insulin sensitivity were measured at baseline and 14 weeks.

Results

Mean ± standard deviation intervention-group body weight decreased 5.8 ± 3.2 kg, compared with 3.8 ± 2.8 kg in the control group (P = .012). In a regression model of predictors of weight change, including diet group and changes in energy intake, thermic effect of food, resting metabolic rate, and reported energy expenditure, significant effects were found for diet group (P < .05), thermic effect of food (P < .05), and resting metabolic rate (P < .001). An index of insulin sensitivity increased from 4.6 ± 2.9 to 5.7 ± 3.9 (P = .017) in the intervention group, but the difference between groups was not significant (P = .17).

Conclusion

Adoption of a low-fat, vegan diet was associated with significant weight loss in overweight postmenopausal women, despite the absence of prescribed limits on portion size or energy intake.

Section snippets

Methods

The study methods have been reported.6, 7 Briefly, 64 overweight or obese (body mass index [BMI] = 26-44 kg/m2) postmenopausal women were recruited through newspaper advertisements in the Washington, DC, area. Premenopausal women were excluded because of possible hormonal effects on metabolic measures.8 Additional exclusionary criteria included unstable medical status, history of eating disorder or substance abuse, severe mental illness, previously diagnosed diabetes, physical conditions

Results

Of the 64 volunteers meeting the participation criteria, 59 completed the study (Table 1). One intervention group participant did not begin the diet, and 2 participants dropped out during the trial. (One could not attend meetings, and the other did not want to continue the diet.) Two control group participants dropped out, both for unspecified reasons. None of the differences between the groups or between completers and noncompleters in baseline body weight or any demographic, anthropometric,

Discussion

Adoption of an ad libitum low-fat, vegan diet in postmenopausal women was associated with a mean weight loss of 5.8 kg in 14 weeks, or 0.4 kg per week, which was significantly greater than that associated with the control diet. This magnitude of weight loss is similar to that observed with reduced-energy (eg, 1200 kcal/day) diets,20 but occurred with no prescribed portion sizes, limits on energy intake, or exercise requirement.

The increased fiber intake and reduced fat intake of the vegan diet

Acknowledgment

The authors thank Paul Poppen, PhD, for the statistical analyses.

References (36)

  • A.H. Lichtenstein et al.

    Relationship of dietary fat to glucose metabolism

    Atherosclerosis

    (2000)
  • P.N. Appleby et al.

    Low body mass index in non-meat eatersthe possible roles of animal fat, dietary fibre and alcohol

    Int J Obes Relat Metab Disord.

    (1998)
  • D. Ornish et al.

    Intensive lifestyle changes for reversal of coronary heart disease

    JAMA

    (1998)
  • N.D. Barnard et al.

    Acceptability of a very-low-fat, vegan diet compares favorably to a more moderate low-fat diet in a randomized, controlled trial

    J Cardiopulm Rehabil.

    (2004)
  • C.J. Henry et al.

    Intra-individual variation in resting metabolic rate during the menstrual cycle

    Br J Nutr.

    (2003)
  • Summary of the second report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel II)

    JAMA

    (1993)
  • Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). National Cholesterol Education Program, National Heart, Lung, and Blood Institute, National Institutes of Health

    (2002)
  • F.E. Thompson et al.

    Dietary assessment resource manual

    J Nutr.

    (1994)
  • Cited by (0)

    The study was funded by The Cancer Project, Washington, DC.

    View full text