People trying to lose weight are often told to eat less, count calories and shrink their portions. But new research suggests there may be another way. A study published in JAMA Network Open found that adults with overweight lost weight while continuing to eat roughly the same amount of food by weight.
Researchers said the key difference was the number of calories packed into each bite, a concept known as energy density. The findings come from a 16-week randomized clinical trial that tested a low-fat vegan diet, with participants able to eat as much as they wanted and without being asked to count calories or restrict portions. "You don't have to eat less," Hana Kahleova, MD, PhD, director of clinical research at the Physicians Committee for Responsible Medicine and lead author, said in a statement.
"You can eat more food, feel full, and still lose weight, by choosing foods that are naturally lower in energy density," she added. According to Statista data for 2026, around 4 percent of the U.S. population follows a vegan diet. Sasha Watkins, a registered dietitian, who was not involved in the study, told Newsweek that this study doesn’t mean you have to go vegan.
Watkins, the head of health at Mindful Chef, highlighted what people are adding to their plates: vegetables, fruit, legumes and wholegrains. She said: “These foods are naturally high in fiber, so they can leave you feeling fuller for longer.” The Institute of Medicine (IOM) recommends between 19 and 38 grams of fiber per day, depending on a person's age and sex. However, research suggests that only around 5 percent of people consume enough fiber to meet those guidelines.
Watkins agrees: “It's important to shift the focus away from calorie counting, which doesn’t suit everyone and can sometimes lead to an unhelpful relationship with food.” She describes “creating more balanced plates” filled with more plants and fiber and variety as a “more sustainable and joyful approach to eating." Neither group received a calorie target or was instructed to limit how much they ate. Researchers calculated dietary energy density by dividing total daily calorie intake by the total weight of food consumed. Energy density refers to how many calories are contained in each gram of food.
By the end of the study, energy density had fallen by around 30 percent among participants following the vegan diet, while remaining largely unchanged in the control group. The researchers also found that calorie intake dropped in both groups, but the reduction was much greater among those following the vegan diet, decreasing by about 357 calories per day. It is important to note that the overall weight of food consumed did not significantly change, suggesting participants were still eating similar quantities of food despite taking in fewer calories.
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