It is now well known that gut bacteria influence our body weight and that faecal transplants can turn lean people into obese or - vice versa - they can save them obese people from otherwise incurable obesity. Specifically, christensenella gut bacteria have been found to be more common in lean people than the overweight and obese and they are also highly inheritable from parent to child. In the lab, christensenella minuta bacteria have turned obese mice into lean mice, and when they were transplanted into bacteria-free obese mice, they reversed their weight gain….