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By Clare Wilson


photka / Alamy

Carbohydrates are one of the three main constituents of the food we eat, along with fat and protein. Carbohydrates can be further divided into sugars, starches and fibre, also known as roughage. Chemically, sugars are small simple molecules, such as glucose and fructose. Starches are built from chains of sugar molecules strung together, while indigestible fibre is made of more complex cross-linked chains.

Dietary guidelines generally advise that we try to get most of our energy from starch, by eating foods such as potatoes, bread, pasta and rice. The thinking is that fat makes us put on weight as it has more calories, and saturated fats found in meat and dairy are particularly bad for us as they increase blood cholesterol levels, which blocks our arteries and causes heart attacks.

But some dieticians are increasingly advocating that we try to limit our dietary carbohydrates and fill up on foods high in protein and fat instead. The strategy has gone under various names, including Atkins, paleo, keto, and Banting, and more recently, “low-carbing”.

A low-carb diet seems to be helpful for people with diabetes, a condition where blood sugar levels are not regulated properly, because starches are quickly digested into their constituent sugars. Low-carbing is now recommended by doctors of several diabetes organisations, such as the American Diabetes Association.

It has also been found to be helpful for weight loss, with some randomised trials finding it works as well, if not slightly better, than traditional low-fat diets.