健康：タバコをやめた後の体重増加に腸内微生物相が関係していた

Changes in the gut microbiota after discontinued exposure to cigarette smoke may underlie excessive body weight gain, suggests a mouse study published in Nature. The findings could improve our understanding of why weight gain often occurs after people stop smoking, but further research in humans is now needed to verify the association.

Cigarette smoking is a leading cause of disease and preventable death in humans globally. Most smokers report a desire or recent attempt to quit, but for many, gaining weight (referred to as smoking cessation–associated weight gain, SCWG) is a major obstacle for long-term abstinence. Previous research has suggested a link between current and past smoking, and gut microbiota changes, but the relevance of such changes for SCWG remains poorly understood.

Eran Elinav and colleagues examined the gut microbiota of mice exposed to cigarette smoke for three weeks, and compared them to those of unexposed mice. The authors found that exposure to smoke remodels the microbiota, which is further altered—but not restored to normal—after smoke exposure ceases. These compositional changes enhanced energy retrieval from the gut and altered the levels of bacterial metabolites, resulting in weight gain even when calorie intake was restricted. Depletion of the gut microbiota with antibiotics prevented SCWG, indicating that weight gain was dependent on the microbiota, while further experiments suggest that non-nicotine components of tobacco are responsible for the effects observed. Similar changes in gut microbiota composition and metabolites were observed in a small group of humans, but this preliminary trial requires confirmation in larger, controlled studies.

The authors suggest that the discovery of this microbiota-dependent mechanism of weight gain following smoking cessation may guide interventions to improve smoking-cessation success, although large trials to establish the relevance of this mechanism in human smokers are now needed.