Obesity has multiple health effects, including increasedTrusted Source cardiovascular risk and risk for mental health conditions such as depression and anxiety.
According to the Centers for Disease Control and Prevention (CDC), 42%Trusted Source of adults in the United States ages 20 and over are obese. What’s more, 73.6%Trusted Source of U.S. adults in the same age demographic are living with either obesity or being overweight.
Losing weight is the main goal of obesity treatments. However, recent literature reviewsTrusted Source report that following initial weight loss, weight regain is typicalTrusted Source.
In addition, a 2001 meta-analysisTrusted Source of weight loss diets found that over 50% of weight loss is regained within 2 years and that over 80% of lost weight is regained within 5 years.
Understanding how to prevent weight regain after dietary restriction could pave the way for improved obesity treatment plans.
Recently, researchers studied the effects of diets with varying protein levels on fat levels in mice following dietary restriction.
Dr. Tonia Vinton, assistant professor of internal medicine specializing in obesity at U.T. Southwestern Medical Center, not involved in the study, told Medical News Today:
“This study suggests that after a short period of dietary restriction — such as intermittent fasting or very low-calorie dieting attempts — a high-protein diet may prevent weight [regain] by increasing Lactobacillus gut bacteria, which [limits] intestinal lipid absorption.”
How dieting leads to weight regain
Prior research, such as this study from 2018Trusted Source, 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.
Effects of protein intake on weight management
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.
Limitations of mouse models
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.”