Should You Eat (or Not) Before Exercising?Food is fuel. Fuel is needed for exercise. So should you eat or fast before hitting the gym or going out for a long run?
The answer: fast.
In the first study of its kind, researchers from the University of Bath in the United Kingdom showed the effects of eating--or not--before exercise on gene expression in adipose tissue (that is, fat issue).
That is, what role does your body fat play in powering your body during exercise?
The study: Two tests were conducted. In the first test, a group of overweight men walked for 60 minutes at 60 percent maximum oxygen consumption on an empty stomach. On a different occasion, the same group of men consumed a high-calorie, carbohydrate-rich breakfast, waited two hours and did the same walk as they did in the first test. In addition to taking multiple blood samples after eating or fasting and after exercising, the researchers collected adipose (fat) tissue samples immediately before and one hour after walking.
The results: Gene expression in the adipose tissue differed significantly in the two trials. The expression of two genes, PDK4 and HSL, increased when the men fasted and exercised and decreased when they ate before exercising. The rise in PDK4 likely indicates that stored fat was used to fuel metabolism during exercise instead of carbohydrates from the recent meal. HSL typically increases when adipose tissue uses stored energy to support increased activity, such as during exercise, explained Dylan Thompson, corresponding author of the study.
Translation: If you eat before you exercise, your fat tissue is so busy responding to the meal you have consumed that it won't have the same positive effect on that fat tissue while you exercise. That means that you should exercise on an empty stomach for the most favorable changes in fat tissue and for the best long-term health benefits.
The study findings were published in the American Journal of Physiology--Endocrinology and Metabolism.
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