46 How’s your fibre intake?

Burn more fat by eating enough of the rough stuff to bolster the bacteria in your gut

it’s not the sexiest-sounding nutrient on the market, but fibre is essential to health and performance — and most of us aren’t getting enough. British people eat around 17g less than the recently increased 30g recommended daily allowance (RDA). Many fibrous foods contain lots of other essential nutrients; those eating a low-fibre diet tend to be missing out on some micronutrients too.

Fibre doesn’t just provide roughage to keep you regular; it’s also a prebiotic — providing food for the bacteria in the gut. Bacterial by-products from fibre, such as short-chain fatty acids, are absorbed and used as energy or even to alter our hormone levels. Without enough fibre, the diversity of bacterial species in the gut is reduced. The type of bacteria in the gut can limit your ability to access fat as fuel while cycling, which in turn may mean you use up your glycogen stores and run out of fuel more quickly. This also means the fat you eat is more likely to be stored as body fat rather than used as fuel.

Studies in mice have shown that those with a diverse bacterial population in the gut — diversity that requires varied sources of fibre — have an increased capacity for exercise compared to mice with limited diversity in their gut bacteria. Training as an endurance athlete is stressful on the body, which is one of the reasons athletes are more likely to suffer from ‘leaky gut’ syndrome, where the gut becomes inflamed and small pieces of food are able to leak through into the circulation, causing inflammation. Fibre helps prevent this from occurring.

It’s perhaps for this reason that Nigel Mitchell, head of nutrition at Cannondale Pro Cycling, has his riders drink a vegetable smoothie daily. Whereas in juices most of the fibrous bulk of ingredients is removed, smoothies contain lots of fibre without requiring riders to eat gargantuan amounts of solid vegetable matter each day.

Although fibre can be associated with bloating and other gastro-intestinal issues, this is generally only a problem if you increase the amount of fibre in your diet suddenly; usually these symptoms soon subside. Building up fibre intake slowly should prevent symptoms.