One decade, we’re told to cut fat from our diets for weight loss. The next, we’re told to count calories. Then it’s all about ditching carbs. But could it be that we’ve had it wrong all along and the secret is actually already within us? More specifically, within our gut?
Tim Spector, a professor of genetic epidemiology and author of The Diet Myth [Hachette], says yes. “The more diverse your gut microbes, the more likely you are to be healthy and lean, and the more sparse your microbes, the more likely you are to be overweight,” Spector says. “This is knowledge that didn’t exist five years ago.”
Welcome to your microbiome.
Each person has up to 2kg of microbes in their stomach and together these microbes make up their unique gut microbiome. The microbes, which include trillions of bacteria, fungi and viruses, help the body produce vitamins and amino acids. They also play an important role in the digestive and immune systems, blood pressure and mental health.
Scientists first discovered that an unbalanced microbiome could lead to obesity in animals. In 2006, researchers from Washington University in the US looked at genetically engineered obese mice and identified that a class of gut microbes called firmicutes were consistently over-represented. These particular microbes were found to be too efficient at extracting energy from food and breaking down fibre, and also increased the absorption of fat.
To put their findings to the test, the team plucked firmicutes from the obese mice and tube-fed them to bacteria-free mice. The latter put on a significant amount of weight over two weeks, even though they ate less. Now there are numerous studies showing that not only are the microbiomes of obese humans lacking in diversity, they are swarming with firmicutes.
A recent study has taken it a step further with “faecal transfers” from humans to mice, which are both gross and fascinating. The study published in the journal Science in 2013 revealed that healthy mice could be made obese by transferring faecal matter, teeming with gut microbes, from obese humans. The research team also found that transferring faecal matter from lean humans prevented mice from putting on weight. . .