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A new study suggests following a Mediterranean diet and getting regular exercise may benefit gut health and lead to weight loss. Darina Kopcok/Stocksy
  • A new study shows adherence to a Mediterranean diet and regular exercise benefited the diversity and composition of the gut microbiome and led to weight loss.
  • The study may point toward a new avenue of research exploring the impact of diet and exercise on gut health.
  • Despite the promising results, experts say the study’s design may have yielded a less definitive finding, and more research is needed.

A new study investigated the effects of combining a Mediterranean diet with exercise and how that impacts the gut microbiome.

The findings show changes in gut microbiota in participants who closely adhered to the Mediterranean diet and engaged in an exercise program compared to those who ate a Mediterranean diet alone.

The people in the diet and exercise group also lost more weight.

A high quality diet and regular exercise are known to benefit overall health.

However, experts say diet is key to weight loss, while exercise benefits cardiovascular, metabolic, and cognitive health, as well as strength and balance.

This would be the first study to suggest a synergistic benefit of diet and exercise for gut health and weight loss if its findings are confirmed.

The study was recently published in The American Journal of Clinical Nutrition.

For the 1-year study, 400 participants ages 55–75 at high cardiovascular risk were divided into two groups of 200 individuals each.

Before the trial, researchers collected dietary information, body measurements, blood samples, and stool samples for microbiota analysis using liquid chromatography-tandem mass spectrometry. Information was collected again at the end of the trial.

The first group, the lifestyle intervention group, was placed on an energy-reduced Mediterranean diet and received personal training advice from a dietitian.

Participants were encouraged to take brisk walks, or the equivalent, for 45 minutes daily and perform specific strength, balance, and flexibility exercises.

In addition, members of the lifestyle intervention group received two monthly visits from researchers, consisting of one group session, one individual session, and one individual phone call.

The second control group was given recommendations for following a Mediterranean diet in two group sessions over the course of the year without any advice regarding physical activity. As a result, their degree of adherence to the Mediterranean diet was up to them, or as the study terms it, ad libitum.

After a year, the researchers found changes in the levels of four metabolites in the stool samples belonging to the lifestyle intervention group compared to the control group.

Levels of two of these metabolites, DPA and adrenic acid, had decreased, while levels of oleic acid and 3-MAA had increased. A reduction of Eubacterium hallii and Dorea microbes was also observed.

The researchers note that some of these differences are associated with changes in some cardiovascular risk factors. Also of interest to the researchers were the metabolic processes, or subnetworks, initiated by these metabolites.

“It has been observed that physical activity has beneficial effects on gut microbiota composition by increasing the abundance of butyrate-producing bacteria or by decreasing the abundance of harmful species,” senior investigator Dr. Jordi Salas-Salvadó, a professor in the Department of Biochemistry and Biotechnology at the University of Southern Catalonia, Spain, explained to Medical News Today.

Despite the promising findings, the different dietary approaches for the lifestyle intervention and control groups make drawing definitive conclusions difficult.

Both groups were supposed to be following the same energy-deficient or calorie-deficient diet.

“If you look at the characteristics and study the results, and look at [their] Mediterranean diet adherence score, it was significantly different [between the two groups], Dr. Babak Firoozi, a board certified gastroenterologist with MemorialCare Medical Group in California, told MNT. Dr. Firoozi was not involved in the study.

“In other words, the control group did not stick to the diet the way the intervention group did,” Dr. Firoozi explained.

Dr. Salas-Salvadó agreed, noting: “The ad libitum nature of the [control group’s] diet could have significantly affected the difference between the microbiota results of the two groups more than the physical activity intervention.”

“An unrestricted diet may introduce variability in nutrient intake, impacting the gut microbiota composition differently than exercise alone. This variability in diet could overshadow the specific effects of physical activity on the gut microbiome, making it challenging to isolate the sole influence of exercise on microbial outcomes.”

— Dr. Jordi Salas-Salvadó, senior study investigator

Dr. Firoozi proposed the study may signal a need for further investigations of the interplay between diet and exercise, although it would need to be structured differently.

He said the findings on the effects of exercise are different from what he believes to be conventional wisdom for gut health.

“I don’t think [the authors] can conclusively say [it was exercise that made the difference], but it definitely is interesting to at least postulate,” Dr. Firoozi said.

Michelle Routhenstein, cardiology dietitian and preventive cardiology nutritionist at EntirelyNourished, not involved in the study, said some evidence has shown that exercise “may help with improving microflora diversity and positively changing the Bacteroidetes: Firmicutes ratio in the gut.”

Still, Routhenstein agreed that further studies are needed.

“In my practice, I encounter individuals who have been lifelong athletes yet suffer from advanced coronary artery disease. Many admit to neglecting their nutrition, prioritizing exercise, and assuming their appearance reflected good cardiometabolic health,” Routhenstein said.

“I believe it’s time to shift our focus away from debating the importance of either exercise or nutrition on cardiometabolic health and instead recognize the significance of both. It’s crucial to understand that optimal heart, gut, brain, and overall health and longevity require a balanced emphasis on both exercise and nutrition.”

— Michelle Routhenstein, registered dietitian nutritionist