on the glycemic index
A glycemic index measures the rate at which carbohydrates get into your blood. A high index food is generally bad because it overloads your blood and hormones with a huge rush of carbs all at once. Foods with a low glycemic index are healthy (even if they have the same amount of total carbs) because the carbs are introduced into the blood at a lower rate.
High amounts of carbohydrates encourages an oversupply of insulin. This is the master hormone which tells your body's cells to store fat for energy.
So, gee, is it any wonder so many of us are overweight?
In fact, given our diets, it's a tribute to our bodies that more of us are not more overweight than we are.
Lack of exercise is certainly a contributing factor. But the real villain behind our epidemic of obesity is the overabundance of high glycemic carbohydrates (generally vegetables have very low indexes, fruits somewhat higher and grains and sugar have very high glycemic indexes).
Plus that's what leads to diabetis, high blood pressures, strokes, heart attacks and possibly cancer and a whole range of chronic diseases.