Eating high-protein meals throughout the day may help you burn belly fat if you combine it with designated fasting days, new evidence indicates.
A protein-pacing diet combined with intermittent fasting led to more fat loss in a study than a standard heart-healthy diet, according to a presentation at ObesityWeek® 2021, the annual conference of the Obesity Society for researchers and clinicians.
Researchers at Skidmore College in New York studied 40 adults who were overweight during an eight-week weight-loss period. Half the participants were assigned a diet in which they ate high-protein meals (at least 25 to 35 grams) four times throughout the day. The meals included protein supplements provided by the research team, such as bars and shakes. Participants prepared their own meals. They were given recipes and instructed to focus on high-quality protein sources like chicken, fish, eggs, Greek yogurt, chickpeas, quinoa, and tofu.
They also fasted either once or twice a week for the first four weeks and once a week for the rest of the study.
The other participants followed a calorie-cutting heart-healthy diet, eating an average of 1,200 to 1,500 calories a day, including 20 to 30 grams of fiber, and limited their fat intake to below 35% of their daily calories. They didn't receive supplements but were given a food stipend and recipes.
While all the groups lost weight, the protein-pacing and fasting group lost significantly more weight overall, despite reducing their calories by roughly the same amount, the study said. They also lost more body fat, about 6% more of their total fat mass, on average, compared with the participants focused only on cutting calories, researchers found.
Fasting could kick-start a fat-loss diet, particularly if you eat protein throughout the day, researchers found More time fasting appeared to have additional benefits. The protein-pacing group that fasted two days a week for the first four weeks lost 27% of their abdominal fat by the end of the study, nearly twice as much as the heart-healthy-diet group and 6% more than the single-day fasting group.
The results suggest metabolic benefits from fasting combined with protein pacing, Paul Arciero, the lead researcher on the study and a professor of health at Skidmore College, told Insider.
"With intermittent fasting, people are usually told not to worry about what they're eating, just when they're eating it," he said. "If you pay more attention to the quality of the calories people eat, it's a game changer."
Some previous studies have found intermittent fasting can lead to weight loss by helping create a calorie deficit. Other evidence suggests fasting doesn't lead to more weight loss than comparable diets after accounting for average calories.
There's evidence that a high-protein diet can aid weight loss, in part, because protein takes more energy to digest than other macronutrients such as carbohydrates and fat.
Protein timing could also promote muscle retention during a diet Protein timing and fasting also led to significant increases in participants' percentage of fat-free mass, researchers found. Fat-free mass includes muscle tissue, which is important to maintain a healthy metabolism and physical strength, while becoming leaner.
"Diets don't discriminate. When we lose weight, we don't get to choose where the weight comes from," Arciero said.
Previous research has suggested protein can help you lose fat on a diet without losing muscle, which can lead to more overall benefits than a focus weight loss alone.
Eating enough protein may be particularly important for fasting, since recent evidence suggests fasting may lead to more muscle loss than other calorie-cutting diets.