The 811 people who took part in the trial were split into four groups. One was assigned to follow a diet that was low in fat and protein. Another followed a diet that was high in fat and protein. The third group adhered to a diet that was high in fat but low in protein, and the fourth group ate a diet that was low in fat but high in protein. The four groups were assigned to consume varying amounts of carbs, ranging from 35 percent of the calories in their diet all the way up to a diet that was 65 percent carbohydrates. All four diets were low in calories and saturated fat.
The research was conducted by Pennington Biomedical Research Center, the Harvard T.H. Chan School of Public Health, and Brigham and Women’s Hospital in Boston.
At the end of the two-year-long trial, the researchers found that the members of each diet group lost a similar amount of weight, averaging about 6.6 to 8 pounds.
But the researchers found that the overweight and obese adults who lost the most weight during the study had several things in common.
They ate more protein.
People who significantly increased the amount of protein they ate lost much more weight than people who did not. By the end of the trial, the high-protein consumers had lost an average of 16.5 pounds – triple the amount that people in the lowest protein group lost.
The reasons? Eating more protein is thermogenic. Our bodies spend a lot of calories digesting and absorbing protein compared with fat and carbs. Protein also increases satiety. When you increase your protein intake, you end up consuming less food, said George A. Bray, a co-author of the study and emeritus director of the Pennington Biomedical Research Center in Louisiana.
They consumed more fiber.
People who increased their fiber intake the most during the first six months of the study lost roughly 23 pounds – nearly double the amount of weight loss seen in people who added the least amount of fiber to their diets.
Fiber causes food to travel more slowly from your stomach to your intestines, which helps you feel full. It also stimulates the release of appetite-suppressing hormones like GLP-1, the hormone that’s mimicked by Ozempic and Wegovy, the popular diabetes and weight loss drugs.
They cut back on ultra-processed foods.
People who consumed the fewest ultra-processed foods lost an average of 18.2 pounds during the study, while those who ate the most ultra-processed foods lost about 11.6 pounds. Previous research has shown that people tend to eat significantly more calories when they’re fed a diet of ultra-processed foods – like cookies, sugary breakfast cereals and soft drinks.
Ultra-processed foods contain additives that can cause people to overeat, and they are less nutritious than fruits and vegetables, grains, beans, and other whole foods.
They embraced variety.
The researchers found that people who ate a wider range of nutritious foods lost significantly more weight and had larger reductions in their waistlines and body fat. These participants increased their intake of foods like whole grains, berries, melons and citrus fruits, as well as low-fat milk, yogurt, and dark-green and orange vegetables. The researchers speculated that people who ate a greater variety of healthful foods were better able to stick with their diets because they experienced more enjoyment and fewer feelings of deprivation.
They walked and exercised more.
Every person in the study was given a pedometer and encouraged to exercise. The researchers found that the more people increased their daily step counts the more weight and body fat they lost. People who had the largest increases in physical activity maintained their weight loss throughout the two-year trial, while those who had the smallest increases in physical activity ended up regaining lost weight.
They got better sleep.
People who struggled with insomnia and other sleep problems had triple the likelihood of failing to lose weight. Previous research has shown that when we lose sleep it can trigger brain and hormonal changes that drive us to crave and overeat junk foods rich in fat and sugar.
The findings from the POUNDS Lost trial demonstrate that these behavioral changes can have powerful effects on your health by sharply reducing your weight, shrinking your waistline and lowering your body fat levels.
The researchers were encouraged when they found that the people who were most successful at losing weight and keeping it off had behaviors in common. Bray said that the relatively straightforward nutrition and lifestyle changes they identified can be implemented by just about anyone and applied to a variety of different diets.
“One of the important points of this paper is that any diet can work for you if you follow it," he said. “There are a few big things that can help make a difference, like eating more protein and fiber and avoiding ultra-processed foods.”
Do you have a question about healthy eating? Email EatingLab@washpost.com and we may answer your question in a future column.
