Good carbs, bad carbs

OK, the carb-bashers were right about some things. But the experts still say that low-carb isn't the way to go. Here's why:

We need carbs Your brain and all your muscles need the glucose they get from carbohydrates to keep you moving and thinking. And most of the vitamins and minerals in our diet come from this food group. That's why 40 per cent of our diet should be carbohydrates, preferably from nutrient-rich fruit, vegetables and whole grains.

The glycemic index may be misleading "There are those who question how relevant the glycemic index is because we don't eat single foods on their own," says Glanville. Combining fat or protein with a carbohydrate, for instance, may actually slow your insulin response.

It's really calories that make you fat Shanthy Bowman, a nutritionist with the United States Department of Agriculture, studied the diet and body mass index of 10,000 people and found the thinnest ate the most carbohydrates. These people also ate more fibre and consumed fewer calories. "It's not the macronutrients that make the person heavy, it's the amount they eat," says Bowman.

Ketosis is dangerous When you're eating next to no carbs, you go into ketosis. You'll lose weight, but ketosis can also lead to bad breath and kidney stones and possibly cause calcium to leach from your bones. Meanwhile, since your brain receives less of the glucose it depends on to function, your thinking could be fuzzy. When your body goes into ketosis, it also mobilizes stores of water. So you lose up to 10 pounds—of water—in a snap, but will put it right back on once you start eating normally again.

You're dieting "My biggest concern with these diets is that obesity is not a short-term problem," says Dr. Shalini Reddy, an assistant professor of medicine at the University of Chicago who has researched high-protein diets. Never mind that cutting out fibre-rich grains and certain nutrient-rich fruit and veggies is bad for your health. When you deprive yourself of that entire category of food, you're going to dive for the cookie jar and chocolate croissants the minute you stray from the diet.