Should you save the oatmeal until after you’ve exercised? A small randomized investigation published in the Journal of Clinical Endocrinology and Metabolism suggests that doing so can noticeably ramp up fat-burning.
The British investigators found that, among 30 men who were overweight or obese, those who exercised in the morning before eating breakfast burned twice as many fat calories during a moderately intense cycling workout as men who ate before working out. That’s because exercising after an overnight fast, when carbohydrate stores are depleted, forces the body to rely more on fat to generate the energy needed for muscle contraction.
While the men who exercised before breakfast had improved insulin sensitivity—which could offer health perks like a lower risk for diabetes—it should be noted that the eat-after group did not lose more weight than the eat-before group during the 6 weeks of the study.
What’s the takeaway? Fasted exercise may improve certain health measures like blood sugar control (at least in people who are overweight). The flip side is that performance may suffer if people can’t push the pace because they are running on fumes. And, in fact, new evidence points to improved muscle performance following a breakfast rich in carbohydrates (see “A Case for Carbs Before Morning Training” in the November–December issue of Fitness Journal). As always, personalizing a program based on the individual is paramount.
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