Breakfast, mothers often say, is the most important meal of the day.
On an individual level that remains true, but scientists are realizing that modern breakfast habits are a major contributor to the epidemic of childhood obesity.
The North American breakfast, typically cereal or toast and jam, consists principally of refined starch and concentrated sugars. These are high-glycemic foods that cause blood glucose levels to soar, then quickly crash, leaving children hungry and fuelling a vicious cycle of overeating and weight gain. Low-glycemic foods release glucose into the body more slowly and evenly, stress the body less and avoid hunger pangs.
"After eating a high-glycemic meal, such as a breakfast cereal, blood sugar rises rapidly, and that causes an outpouring of the hormone insulin," said David Ludwig, an international obesity expert and director of the Optimal Weight for Life program at Boston Children's Hospital. "Insulin, in turn, drives the blood sugar down over the next three to four hours into the range sometimes below where it started (hypoglycemia). The body's response to low blood sugar is to secrete stress hormones and increase hunger."
Research in recent years has demonstrated this point time and time again, and renewed interest in the importance of breakfast.
Jeya Henry, a professor of human nutrition at Oxford Brookes University, in Oxford, England, demonstrated the impact of a low -glycemic breakfast on British schoolchildren in a recent study.
He found that children who ate a low-glycemic breakfast of oat porridge, Swiss-style muesli or whole-grain bread made with soybeans, remained satiated far longer than those who ate a high-glycemic breakfast of corn flakes.
What's more, Dr. Henry found that children who had the low-glycemic breakfast ate considerably less at lunch, even when they were offered an all-you-can-eat buffet.
"By manipulating the kinds of breakfasts we give our children, you can unobtrusively reduce their food intake at lunchtime," he said. "You could then think of a situation that you give them a low-glycemic lunch, which would also have an effect on their dinner, and so on."
The message to retain, Dr. Henry said, is that providing children with low-glycemic food reduces their overall food intake while actually improving their nutrition.
Dr. Ludwig did similar research with obese adolescents, offering them unlimited access to foods, but giving one group low-glycemic fare and the other more traditional high-glycemic food.
Those in the low-glycemic group, while they were not on a diet as such, ate fewer calories and saw their weight drop and their risk of diabetes fall.
Research on adults, in particular people with health conditions such as obesity, heart disease and diabetes, has found similar results.
"We know of absolutely no downside to reducing the glycemic index of our diet," Dr. Ludwig said. "In fact, the food that we recommend — fruits, veggies, nuts, legumes — have all sorts of beneficial health effects independent of glycemic index."
While the knock against the glycemic-index approach is that it is too complicated, even its most avid proponents say it is unnecessary to follow charts rigidly to know what foods have a low glycemic index.
"It's fairly easy to realize that frosted twinkles and so on that pass as breakfast cereals are going to be at the high end and be unhealthy," said David Jenkins, director of the risk behaviour modification centre at St. Michael's Hospital and a glycemic-index pioneer.
The high degree of cooking and processing of many commercial breakfast cereals, hot and cold, tends to make the starch in them more easily digestible and drives up their glycemic-index value.
"On the other hand, you also know that unprocessed, high-fibre cereals are going to be in the mid-.to low range. And, of course, nothing beats good old stick-to-your-ribs oatmeal," Dr. Jenkins said.
The researcher said that as public-health officials struggle to find solutions to the epidemic of childhood obesity, they will turn their attention to the breakfast table, because it is key to eating well. "It reinforces that breakfast is the most important meal of the day, in ways that many of us never imagined."
With reports from Avis Favaro, medical reporter at CTV News, and Jenny Wells, a CTV producer. Part two of a three-part series.
Yesterday: Glycemic index challenges the anti-carb movement.
Tomorrow: Labelling foods for the glycemic index.
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