The claim: A growling belly during your workout may be a sign you’re cheating yourself out of a greater calorie burn, according to new research published in the Journal of Science and Medicine in Sport.
The research: Ten “recreationally active” (non athletes) college-age women of normal body weight were given a high protein meal (45% protein), low protein meal (15%), or no food at all before walking on a treadmill. The women who ate the high protein meal an hour prior to working out burned more calories per minute than women who ate nothing. (No difference was found between the low-protein group and the fasting women.) The additional calorie burn amounted to 185 calories over the following 24-hour period.
What it means: “The body will use more calories when you have additional calories to expend (i.e. after eating),” says lead study author Ashley Binns, a PhD student. Assuming you ate the same amount of total daily calories, the additional calorie burn could add up to a 15-pound weight loss over the course of a year. Although fasting before exercise has been used as a method for weight loss, the body breaks down muscle and/or fat as fuel sources if we do not eat food prior to exercising, says Binns. “This could potentially result in muscle weight loss.” And less muscle means less calorie burn.
The bottom line: Plan to eat a high-protein snack an hour before your workout to burn more calories during exercise. The exact recommended amount of protein is still up for debate, however, says Binns. “Many studies suggest consumption of upward of 30 grams of protein spread throughout the day across three meals is ideal for maintenance of weight and/or weight loss.” Good high-protein foods include protein drinks, egg whites, peanut butter, or Greek yogurt. An example of a breakfast that meets the 45% protein used in the study: one whole egg and two egg whites, plus two pieces of toast with butter, and orange juice.