With three young children, his spouse working full-time, and shift work to juggle, Mark Stewart has a busy life. So there is little hesitation when it's his turn to prepare dinner: He gets the water boiling, cuts the vegetables for the sauce, and has a big batch of spaghetti on the table in no time.
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In this anti-carbohydrate era, when it has become gospel that carbs are the express lane to obesity, these are the words of a heretic: doubly so because he shuns red meat and more than half his diet consists of carbs including pasta, whole-wheat breads and fresh fruits and vegetables.
But Mr. Stewart, a Toronto firefighter, has many things that the Atkinsites, the South Beachers, the Zonies and followers of other trendy diets can only long for: a trim, buff body, boundless energy, good blood pressure and rock-bottom cholesterol.
What he has realized is that carbohydrates are not the monolithic evil they are made out to be: There are good carbs and bad carbs.
The good ones are those that break down slowly in the body and provide a steady source of energy. The bad ones give you a quick rush and leave you feeling hungry again not long after.
What he is doing, almost unwittingly, is choosing food based on its glycemic index, a measure of the speed at which food is digested and converted into glucose, the body's source of energy. It is a Canadian theory that has a devoted and growing following in scientific circles, and that is now entering the mainstream as a counterbalance to carbless mania.
GI has also spawned some of the hottest new entries in the diet book wars, with titles including The New Glucose Revolution, by University of Toronto professor Tom Wolever, and The GI Diet, by Rick Gallop, past president of the Heart and Stroke Foundation. What distinguishes GI from its competitors, however, is that it is more a scientific theory than a weight-loss fad.
"It's not a diet; it's a way of thinking of food," said David Jenkins, a world-renowned nutritional scientist and director of the Risk Factor Modification Centre at St. Michael's Hospital in Toronto.
He published the first research on the glycemic index in 1981, but, in his words, "it sank like a stone." Over the years, however, the evidence slowly accumulated as Dr. Jenkins and others published groundbreaking work on how dietary choices influenced rising rates of obesity, diabetes, heart disease and some forms of cancer.
Today, the GI approach is being hailed as the missing piece of the nutritional puzzle, the underlying explanation for why the high-carb, low-fat and carb-free approaches have all failed.
"This is emerging as one of the most promising, if not the most promising nutritional development ever," said Simin Liu, an assistant professor in the department of epidemiology at the Harvard School of Public Health.
The body converts all carbohydrates -- bread and sugar alike -- into sugar molecules that are burned or stored. The faster carbs are broken down by the digestive system, the quicker blood sugar goes up and the higher the GI of a given food. The GI value of pure glucose is set at 100, and every other food is ranked on a scale of 0 to 100 based on the actual effect on blood glucose levels.
Almonds rate a 0, apple juice 30, spaghetti 38, cheese pizza 60, Coca-Cola 63, a white bagel 72, a baked potato 85, and a fruit roll-up 99.
The blast of sugar that comes from high GI foods makes insulin levels go up and stresses the pancreas, our body's insulin factory. Insulin is a hormone that activates cells to absorb sugar in the form of glucose. This, in turn, leads to insulin resistance, a precursor of diabetes and heart disease.
"At least 25 per cent of the population is insulin-resistant, and half are overweight or obese," Dr. Liu said. "This indicates they can't handle the high glycemic load."
