Low-Fat Vegan Diet Cuts Energy Density, Enables Weight Loss Without Portion Limits

A 16-week randomized clinical trial published in *JAMA Network Open* examined adults with overweight who followed a low-fat vegan diet. Participants were allowed to eat “as much as they wanted” and received no calorie targets or portion-size instructions. A control group continued their usual diets under the same unrestricted conditions.

Newsweek

Researchers defined dietary energy density as total daily calories divided by the total weight of food consumed. Participants in the vegan arm replaced meat, dairy, and eggs with vegetables, fruits, legumes and whole grains—foods naturally higher in water and fiber, which lower calories per gram. The study measured the change in energy density over the trial period.

Newsweek

By the study’s end, the vegan group’s energy density fell by roughly 30 %, while the control group’s remained largely unchanged. Calorie intake dropped in both groups, but the vegan participants reduced intake by about 357 calories per day. Despite these reductions, the overall weight of food eaten did not change significantly, indicating participants ate similar quantities of food. The lower energy density was linked to greater weight loss, a relationship that persisted after accounting for calorie-intake changes.

Newsweek

Registered dietitian Sasha Watkins, head of health at Mindful Chef, noted that the study does not require a vegan diet; she highlighted that high-fiber plant foods such as vegetables, fruit, legumes and whole grains promote satiety. Watkins also pointed out that the Institute of Medicine recommends 19–38 g of fiber per day, yet only about 5 % of people meet this guideline.

Newsweek

• “This helps answer a question people often have about plant-based eating: How can you lose weight without counting calories or going hungry?” — Hana Kahleova

Newsweek

• “When the foods you eat are lower in energy density, your body's natural appetite signals work in your favor,” — Hana Kahleova

Newsweek