Phys Ed: The Benefits of Exercising Before Breakfast

The holiday season brings many joys and, unfortunately, many countervailing dietary pitfalls. Even the fittest and most disciplined of us can succumb, indulging in more fat and calories than at any other time of the year. The health consequences, if the behavior is unchecked, can be swift and worrying. 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.

For the study, researchers in Belgium recruited 28 healthy, active young men and began stuffing them with a truly lousy diet, composed of 50 percent fat and 30 percent more calories, overall, than the men had been consuming. Some of the men agreed not to exercise during the experiment. The rest were assigned to one of two exercise groups. The groups’ regimens were identical and exhausting. The men worked out four times a week in the mornings, running and cycling at a strenuous intensity. Two of the sessions lasted 90 minutes, the others, an hour. All of the workouts were supervised, so the energy expenditure of the two groups was identical.


Their early-morning routines, however, were not. 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.

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