Slimming significantly alters your microbiome and brain activity

Worldwide, more than one billion people are obese. Obesity is a risk factor for cardiovascular disease, diabetes, and some cancers. But permanently losing weight isn’t easy: complex interactions between body systems such as gut physiology, hormones, and the brain are known to work against it. One method for weight loss is intermittent energy restriction (IER), where days of relative fasting alternate with days of eating normally.

“Here we show that an IER diet changes the human brain-gut-microbiome axis. The observed changes in the gut microbiome and in the activity in addition-related brain regions during and after weight loss are highly dynamic and coupled over time,” said last author Dr Qiang Zeng, a researcher at the Health Management Institute of the PLA General Hospital in Beijing.

First, the participants underwent a ‘high-controlled fasting phase’ of 32 days where they received personalized meals designed by a dietician, with a caloric value decreasing stepwise to one quarter of their basic energy intake. They then spent 30 days in a ‘low-controlled fasting phase’, where they were given a list of recommended foods: participants who adhered perfectly to this diet would receive 500 calories per day for women and 600 calories per day for men.

By the end of the study, their body weight had decreased by an average of 7.6kg, or 7.8%. As expected, they had undergone reductions in body fat and waist circumference.

These results suggest that changes in the brain and microbiome during and after weight loss are linked – either because they cause each other, or because an unknown other factor causes both. Because the study is correlational, it can’t resolve the direction of the underlying causality.

Reference: Slimming significantly alters your microbiome and brain activity; Frontiers in Cellular and Infection Microbiology; DOI: 10.3389/fcimb.2023.1269548