Examining the role of gut microbial composition and function in weight loss

Feb. 16, 2019

Researchers know that the pathophysiology of obesity is complex, with several host genes and environmental factors playing a role. Lifestyle interventions, including a combination of dietary restrictions, physical exercise and behavioral therapy, are often the first step that providers recommend to address obesity. However, this approach fails to help many individuals achieve significant and sustained weight loss, a fact that is often attributed to patient adherence.

Taking a closer look at this phenomenon, Mayo Clinic researchers wondered if there may be other factors at work that prevent patients from responding to traditional weight-loss strategies. In a preliminary study published in Mayo Clinic Proceedings, Mayo researchers decided to test whether certain functions performed by the gut microbiota may be associated with the inability of some individuals to lose weight.

"We know that some people don't lose weight as effectively as others, despite reducing caloric consumption and increasing physical activity," says Purna C. Kashyap, M.B.B.S., a gastroenterologist at Mayo Clinic's campus in Rochester, Minnesota, and senior author of the study. "Gut bacteria have the capacity to break down complex food particles, which provides the body with additional energy," Dr. Kashyap says. "However, we hypothesized that for some individuals trying to lose weight, this process may become a hindrance."

Study methods

The Mayo Clinic research team recruited a group of 26 adults to participate in a lifestyle intervention program for weight loss. Participants had a body mass index of 27 to 39.9 kg/m2 and were enrolled in the Mayo Clinic Obesity Treatment Research Program between August and September 2013.

Exclusion criteria included:

  • Health problems preventing individuals from engaging in physical activity
  • Previous operations for managing obesity (bariatric procedures, gastric bypass)
  • Concurrent participation in another weight-loss program
  • Use of weight-loss medications within the previous 30 days
  • Use of antibiotics within the previous 30 days
  • Use of proton pump inhibitors, laxatives, statins and analgesics

The physical activity intervention involved recommendations to walk at least 10,000 steps a day or the equivalent, monitored with a pedometer. Behavioral intervention was delivered through weekly group sessions modeled after the Look AHEAD protocol and included self-monitoring, goal setting, stress reduction, social support, and so on.

Preliminary findings

Mayo researchers collected clinical, biochemical and demographic information from participants at baseline and after three months. The percent weight loss after three months was calculated on the basis of the participant's baseline body weight. Success was defined as a weight loss of at least 5 percent or more at three months.

Researchers compared clinical characteristics and gut microbial composition and function in participants who achieved weight-loss success and those who did not. Dr. Kashyap and colleagues found that gut bacteria among individuals who did not lose weight were different from gut bacteria in participants who lost weight:

  • After three months, nine of 26 participants lost at least 5 percent of their weight. The mean weight loss was 7.89 kg (95 percent confidence interval, 6.46-9.32 kg) in the group that lost more than 5 percent weight and 1.51 kg (95 percent confidence interval, 0.52-2.49 kg) in the group that did not.
  • An increased abundance of phascolarctobacterium was associated with weight-loss success.
  • An increased abundance of dialister and of genes encoding gut microbial carbohydrate-active enzymes was associated with failure to lose 5 percent body weight.

"While we are aware there are several lifestyle factors that can contribute to failure, these results suggest that gut bacteria may also be a determinant of weight loss in response to diet and lifestyle changes," Dr. Kashyap says. "More specifically, a gut microbiota with increased capability for carbohydrate metabolism appears to be associated with decreased weight loss."

Dr. Kashyap emphasizes that this is a preliminary finding in a small study, and more research is needed to confirm the role of gut bacteria in weight loss. "While we need to replicate these findings in a bigger study, we now have an important direction to pursue in terms of potentially providing more-individualized strategies for people who struggle with obesity," says Dr. Kashyap.

For more information

Pedrogo DAM, et al. Gut microbial carbohydrate metabolism hinders weight loss in overweight adults undergoing lifestyle intervention with a volumetric diet. Mayo Clinic Proceedings. 2018;93:1104.