ByLucy Notarantonio
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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 vegandiet, 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
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“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 Newsweekthat 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.”
What the Researchers Found
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
Why Energy Density Matters
Scientists have long been interested in energy density because it can influence both hunger and calorie intake
Foods with a lower energy density typically contain more water and fiber, allowing people to eat larger portions for fewer calories: vegetables, fruits and legumes are common examples
According to the researchers, participants in the vegan group replaced calorie-dense foods such as meat, dairy and eggs with foods that provided more volume for fewer calories
“This helps answer a question people often have about plant-based eating: How can you lose weight without counting calories or going hungry?” Kahleova said. “The answer is energy density. Plant foods are rich in water and fiber, so you can fill your plate, feel full, and still take in fewer calories.”
Weight Loss Without Portion Control?
The study found that larger reductions in energy density were linked to greater weight loss. That relationship remained even after researchers accounted for changes in calorie intake
Kahleova said the findings suggest weight management may not always require strict portion control
“This isn’t about willpower or smaller portions,” she said. “It’s about choosing foods that naturally deliver fewer calories in every bite. A 30 percent reduction in energy density is a substantial shift that would be very hard to achieve and sustain through portion control alone.”
Controlled feeding studies have previously shown that lowering the energy density of meals can help people feel full while reducing overallcalorie consumption
“When the foods you eat are lower in energy density, your body‘s natural appetite signals work in your favor,” Kahleova said, adding: “You eat until you’re satisfied, and you simply end up with fewer calories. That’s a sustainable way to manage weight.”
Contact Newsweek editors on this story:Charlotte Nisbetand Cristina Diciu
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