Low-fat vegan diet cut 357 calories/day in trial
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- JAMA Network Open published a 16-week randomized trial in which adults with overweight on a low-fat vegan diet consumed about 357 fewer calories per day than a control group, despite eating roughly the same total weight of food.
- Hana Kahleova, MD, PhD, director of clinical research at the Physicians Committee for Responsible Medicine, led the study; neither group received a calorie target or instructions to limit how much they ate.
- The vegan diet reduced dietary energy density — calories per gram of food — by roughly 30%, while the control group's energy density remained essentially unchanged.
- Neal D. Barnard is a co-author on the paper; the intervention diet removed calorie-dense animal products like meat, dairy, and eggs while emphasizing water- and fiber-rich fruits, vegetables, grains, and legumes.
- Greater reductions in energy density were associated with greater weight loss, and that relationship held even after researchers statistically controlled for changes in calorie intake — pointing to food composition, not just volume eaten, as the driver.
- Neither group significantly changed the total weight of food they ate, meaning the vegan participants took in fewer calories without reducing how much they ate by volume.
Why it matters: For clinicians counseling patients who struggle with calorie counting, this trial reframes weight loss as a food-composition problem rather than a willpower one: a 30% drop in calories-per-gram from plant foods drove 357 fewer daily calories and weight loss without portion restriction or hunger.
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