New Perspectives on Weight Loss and Diet Composition

Traditional weight-loss advice has often focused on eating less. Recent research offers a different approach, suggesting weight loss is possible without lowering food intake if the diet composition changes. A study in JAMA Network Open determined that individuals with overweight who adopted a low-fat vegan diet shed pounds while maintaining their daily food intake.

Dr. Hana Kahleova, the lead author and director of clinical research at the Physicians Committee for Responsible Medicine, explained the concept of energy density. This refers to the calories contained per gram of food. Kahleova noted that people tend to maintain consistent food weight or volume per meal, regardless of calorie content. Foods rich in water and fiber—such as vegetables, fruits, legumes, and whole grains—allow consumption of satisfying meal volumes with fewer calories than those based on meat, cheese, and processed foods.

The study was a secondary analysis of a 16-week randomized clinical trial involving 244 overweight adults. Participants were assigned to either a low-fat vegan diet, focusing on fruits, vegetables, grains, and legumes, or to continue their regular eating habits. No calorie limits or restrictions were imposed. Participants on the vegan diet consumed the same amount of food by weight but saw a nearly 30 percent decrease in energy density.

Vegan participants experienced an average energy intake reduction of 357 calories daily, without changing the food amount by weight. This highlights that shifting the type of food can naturally lower calorie intake.

Dr. Kahleova shared recommendations for adapting these findings without fully adopting a vegan diet. Prioritizing foods high in water and fiber and reducing calorie-dense options are key. She suggested filling half the plate with vegetables before other items, swapping meat for beans, lentils, or tofu in some meals, choosing whole fruit over juice or dried fruit, and using oils, butter, and cheese sparingly. Fat contains more than double the calories per gram compared to carbohydrates or proteins, making it the largest factor in energy density.

Participants were not required to count calories or follow specific calorie targets. Adjusting food types led naturally to reduced calorie intake.

Reference: Kahleova H, Znayenko-Miller T, Maracine C, Holubkov R, Barnard ND. Vegan Diets and Dietary Energy Density: A Secondary Analysis of a Randomized Clinical Trial. JAMA Netw Open. 2026;9(8):e2627483. doi:10.1001/jamanetworkopen.2026.27483.

Contact Newsweek editors on this study: Kara Dolman and Gray R. Thomas