Risk of Overweight and Obesity Among Vegetarians

There is truth in the old adage that we are what we eat. A team led by Dr. P.K. Newby recently found that women who are semi-vegetarians, lactovegetarians, and vegans have a lower risk of overweight and obesity than do omnivorous women (Am J Clin Nutr 2005;81:1267).

According to the authors, surprisingly few studies have rigorously examined the relationship between a vegetarian eating pattern and obesity. Questions also remain as to whether animal products such as lean protein and dairy foods are helpful for controlling weight. In addition, recent studies have also shown a protective effect of dietary fiber and whole grains as well as dairy products and calcium.

The study group

The cross-sectional study used data from more than 55,000 healthy women participating in the Swedish Mammography Cohort. The participants were asked whether they considered themselves to be omnivores (eating all types of foods), semi-vegetarians (mostly lactovegetarians, who sometimes consume fish or eggs), lactovegetarian (consuming no meat, poultry, or fish or eggs), or vegans (consuming no meat, poultry, fish, eggs, or dairy products).

Results: Omnivores were heavier

A small percentage of women were semi-vegetarian (1.7%), lactovegetarian (0.29%), or vegan (0.15%). The omnivorous women were significantly heavier (mean: 10.9 kg heavier) than any of the vegetarian women. Mean weight, body mass index (BMI), and prevalence of overweight and obesity were highest among omnivores compared with any of the vegetarian groups. All three vegetarian groups had average BMIs lower than those of the omnivorous women. The authors noted that the vegans may be at an even lower risk of overweight or obesity than the semi- and lactovegetarians (66% risk reduction compared with 48% and 46%, respectively).

Food and nutrient intakes were significantly different across the three groups of vegetarian women. All of the vegetarian groups had higher intakes of fruit, vegetables, and fiber and lower intakes of fat and protein than women who were omnivores.

Not all carbohydrates are alike

The authors stress that it is important to differentiate between types of carbohydrate when evaluating dietary patterns, including weight loss diets. Current fad diets that promote low carbohydrate intake ignore the fact that whole and refined carbohydrate foods evoke different metabolic responses, and have different effects on appetite and energy intake. This study and others suggest that a high-carbohydrate diet may be protective against obesity if the carbohydrate originates from fiber-rich foods such as fruit, vegetables, and whole grains.