Weight loss: Increased protein intake may prevent weight regain after a diet

Prior research, such as this study from 2018, suggests that some diets may promote weight regain by altering gut bacteria composition.

For the present study, researchers investigated how dietary restriction followed by limitless feeding affected fat mass. They found that refeeding after dietary restriction led to a quick build-up of fat.

From further experiments, they noted that increases in fat levels occurred due to increased fat absorption in the intestines as opposed to increased food intake.

Next, the researchers analyzed blood samples from mice before, during, and after short-term dietary restriction to identify potential ways to sustain weight loss.

They found that certain amino acids in the blood increased during and after dietary restriction.

To understand how protein levels may influence post-diet fat absorption, the researchers fed mice a high-protein diet, a normal-protein diet, or a low-protein diet after a short-term dietary restriction.

They found that high-protein diets were most effective in preventing quick weight regain and also partially maintained weight loss thereafter.

To understand how a high-protein diet reduces weight regain, researchers analyzed its effects on energy expenditure. Mice fed normal protein diets had higher energy expenditure than those on a high-protein diet, indicating that the benefits of a high-protein diet came from elsewhere.

From further tests, they found that high-protein diets decreased intestinal fat absorption.

The researchers next analyzed fecal samples from mice fed high amounts of protein and normal amounts of protein following dietary restriction. They found that mice on normal diets had higher levels of Lactobacillus bacteria than mice on high-protein diets.

To see whether Lactobacillus levels influenced weight regain the researchers treated mice with penicillin for a week before placing them on restrictive diets. They found that penicillin reduced Lactobacillus without affecting other bacteria and significantly reduced intestinal fat absorption afterward.

The researchers concluded that targeting Lactobacillus after dietary restriction with a high-protein diet or antibiotics could prevent obesity after dieting.

Dr. Vinton said the protein strategy used in the study could seem appealing to those who want to lose weight, but noted that data is still limited to support the approach.

When asked about the study’s limitations, John P. Thyfault, Ph.D., Professor of Cell Biology and Physiology at the University of Kansas Medical Center, not involved in the study, told MNT:

“The role of reduced bile acids and the role of increased microbiota species Lactobacillus to change lipid digestion and absorption are of interest but would need to be validated in human subjects. Moreover, using a probiotic to knockdown Lactobacillus is a non-targeted approach that could be impacting a host of other mechanisms.”

Dr. Aleem Kanji, board-certified internist and endocrinologist at Ethos Endocrinology, Houston, TX, not involved in the study, also told MNT that the results may be further limited as the mice studied were not models of obesity.

“Ideally, mice models that are obese at baseline and subsequently undergo dietary restriction and refeeding would be evaluated,” he noted.

Dr. Keta Pandit, board-certified endocrinologist, and obesity medicine specialist at Texas Diabetes and Endocrinology, Austin, Texas, also not involved in the study, told MNT that the study does not account for human behavior, which differs from that in mice.

“Behaviors such as cravings, satiation, [and] hunger play a major role in [sustained] weight loss and in weight regain. When people pursue weight loss goals, they also increase exercise,” Dr. Pandit noted.

“That has not been factored in, [however] the type of exercise is also critical in a weight loss journey.”

To keep weight off following a diet, Dr. Kanji recommends patients consume sufficient levels of protein. While this is not necessarily higher protein, he noted it is a sufficient amount based on a person’s body composition.

“Sufficient protein intake helps preserve lean body mass during the active phase of weight loss. Preservation of lean body mass promotes overall health and quality of life, particularly as we age,” said Dr. Kanji.

Krista Varady, Ph.D., professor of nutrition at the University of Illinois Chicago, not involved in the study, noted five points to keep weight off long-term:

• eating less processed foods
• eating more fruits and vegetables
• walking at least 8,000 steps per day
• knowing your calorie needs, and tracking calories using a food app
• cooking at home instead of eating at restaurants

Meanwhile, Dr. Pandit recommended patients approach obesity as a chronic medical condition as opposed to a temporary life obstacle.

Lifestyle habits, such as increasing exercise levels and eating a well-balanced meal high in protein and fiber, are crucial to maintaining weight loss, Dr. Pandit said.