Exercising before breakfast blunts the deleterious effects of overindulging. Exercising in a fasted state induces the body to burn a greater percentage of fat for fuel during vigorous exercise, instead of relying primarily on carbohydrates. The fasting group also showed increased levels of a muscle protein that would increase insulin sensitivity and limit insulin resistance seen in type II diabetes.
A recent study by scientists in Australia found that after only three days, an extremely high-fat, high-calorie diet can lead to increased blood sugar and insulin resistance, potentially increasing the risk for Type 2 diabetes. Waistlines also can expand at this time of year, prompting self-recrimination and unrealistic New Year’s resolutions.
But a new study published in The Journal of Physiology suggests a more reliable and far simpler response. Run or bicycle before breakfast. Exercising in the morning, before eating, the study results show, seems to significantly lessen the ill effects of holiday Bacchanalias. One of the groups ate a hefty, carbohydrate-rich breakfast before exercising and continued to ingest carbohydrates, in the form of something like a sports drink, throughout their workouts. The second group worked out without eating first and drank only water during the training. They made up for their abstinence with breakfast later that morning, comparable in calories to the other group’s trencherman portions.
The experiment lasted for six weeks. At the end, the nonexercising group was, to no one’s surprise, super-sized, having packed on an average of more than six pounds. They had also developed insulin resistance — their muscles were no longer responding well to insulin and weren’t pulling sugar (or, more technically, glucose) out of the bloodstream efficiently — and they had begun storing extra fat within and between their muscle cells. Both insulin resistance and fat-marbled muscles are metabolically unhealthy conditions that can be precursors of diabetes.
The men who ate breakfast before exercising gained weight, too, although only about half as much as the control group. Like those sedentary big eaters, however, they had become more insulin-resistant and were storing a greater amount of fat in their muscles. Only the group that exercised before breakfast gained almost no weight and showed no signs of insulin resistance. They also burned the fat they were taking in more efficiently. “Our current data,” the study’s authors wrote, “indicate that exercise training in the fasted state is more effective than exercise in the carbohydrate-fed state to stimulate glucose tolerance despite a hypercaloric high-fat diet.”
Phys Ed: The Benefits of Exercising Before Breakfast