A microscopic solution – The best gut bugs to lose weight

Scientists have identified a microscopic universe of tiny microbes in our gut that seems to have a great deal to do with our weight, as Celeste McGovern has discovered

Rob Knight used to be paunchy. He was about 80 pounds overweight, in fact, when he and his girlfriend Amanda took a trip to Peru in 2008. The couple backpacked up the Inca Trail to the Amazon, where they were beset by a nasty bout of diarrhoea. They seemed to recover, then it flared up again, and both took the same antibiotic to get rid of the bug.

When they returned home, the couple resumed their usual diet and exercise, except Knight started losing weight—a lot of it. Over the next few months he dropped nearly six stone (84 pounds) and effortlessly went from obese to a healthy body weight. While he was downsizing his trousers, Amanda lost no weight at all.

“I believe the difference was related to a radical change in my microbes,” Knight relates in his book, Follow Your Gut (Simon & Schuster, 2015). “We each responded differently to the same disease and the same course of treatment.”

It’s an educated guess. Knight, a professor at the University of California at San Diego, is an expert on human microbes, tiny single-celled organisms including bacteria and viruses. He is also co-founder of the American Gut Project, a crowd-funded endeavour that has begun to chart all those microbes residing in and on the human body. (British Gut is the UK counterpart with the same objective.)

Thanks to new DNA-sequencing technologies, scientists are able to explore what is turning out to be a vastly greater microscopic world within humans than they ever imagined. And their first glimpses are revealing that the microscopic life forms inside us are astonishingly numerous and diverse.

Our bodies comprise around 10 trillion human cells, for example, but there are about 100 trillion microbes in our ears, eyes, noses, belly buttons and especially our guts. It turns out that these microbes—collectively known as our ‘microbiota’—and their millions of genes—the ‘microbiome’—are far more important than medical textbooks have acknowledged.

Indeed, while doctors continue to cavalierly prescribe antibiotics in record numbers, a huge body of research is proving that the microbes they are attacking are crucial to our health, regulating our immune systems and preventing disease, digesting our food, manufacturing vitamins and affecting everything from our mental health to our weight.


The microbiome and its impact on obesity is one of the fastest moving areas of study, perhaps because it is one of the fastest growing epidemics of our time and linked to myriad other soaring health conditions, including heart disease, diabetes, cancer, musculoskeletal diseases, depression, anxiety and decreased life expectancy. It is estimated that obesity already costs the National Health Service (NHS) upwards of £5 billion per year and, last year, a public-health study revealed that by their eleventh year, a third of British school children are already overweight or obese…

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