You’ve probably heard the claim that exercising on an empty stomach helps boost fat loss. But is there any truth to it? While the answer depends on who you talk to (and what book you read — so many weight-loss books promote the practice), most research studies and exercise science experts agree that fasting before working out is counterproductive.
Working out on an empty stomach makes sense — in theory. Proponents say that you’ll burn more fat because your body doesn’t have carbohydrates to use as energy since you haven’t eaten. However, a February 2019 report published in Strength and Conditioning Journal found that to be untrue. Researchers found that when you don’t have proper fuel in your body, your body has less energy and therefore your exercise intensity and number of calories burned suffers. During intense workouts, your body may actually pull protein from your muscle for fuel — definitely counterproductive since muscle helps to rev metabolism.
In addition, another study from 2002 published in the International Journal of Sport Nutrition and Exercise Metabolism found that women who ate 45 grams of carbohydrates before a workout actually ending up eating less throughout the rest of the day than those who didn’t have a pre-workout meal or snack. Personal trainer and owner of Fitness 121 in Roseland, New Jersey, Francesca Pucher says that finding the right meal or snack before a workout is key for optimal fat burn.
“Now I don’t recommend eating a fatty BLT or a greasy Egg McMuffin, but something small that your body can digest properly, and still give you energy — like a piece of whole-grain toast and natural peanut butter, or a Greek yogurt or even a natural energy bar,” Pucher says. “But exercising on an empty stomach will just cause you to overeat when the workout is complete, and if we are looking to burn fat, that is not the answer.”
Jenny Skoog, fitness expert and owner of SkoogFit, agrees, adding that when you eat your meal is important, too.
“Simply put, the body needs energy to burn energy and you get a higher quality workout with a little foresight,” Skoog says. “My suggestion? Have a 150-calorie snack an hour before working out, like half of a banana and one tablespoon of almond butter or half of an energy bar.”
What you eat after a workout is also of uptmost importance for fat loss over the long haul, says Holly Perkins, New Balance Fitness Ambassador. She recommends getting protein and carbs after exercise so that you have the energy and fuel to make your next workout strong. Watch our full interview with Perkins discussing properly fueling for a workout here.
“It’s all about recovery,” Perkins says. “The trick is, if you don’t recover right, your workout is going to suffer tomorrow.”
In a nutshell, when you fuel properly, you can workout harder and longer, thereby improving your fitness and building your muscle mass, which burns fat. What’s your favorite pre- or post-workout meal or snack?