The Truth About Exercise and Breakfast

The answer will change the way you think about your morning meal.

21 March, 2018
The Truth About Exercise and Breakfast

Ask 20 different people what they eat before they exercise, and you'll get 20 different answers: That's because the best thing to put into your body before a workout is widely considered — by humans and many experts — a matter of personal preference.

One writer, for instance, says she runs 4.5 miles a day on an empty stomach, often pushing herself through vicious hunger pangs, only to reward herself with a calorie-bomb of a doughnut and a requisite coffee at the finish line.

But are there any actual benefits to suffering through the grumbles? Certified strength and conditioning specialist Brad Schoenfeld, PhD, author of the best-selling books, Sculpting Her Body Perfect,who's done extensive research on the technique, doesn't think so.

Known as fasting cardio, or aerobic exercise performed on an empty stomach about 12 hours after your last meal, some athletes think this strategy will turn their bodies into a more efficient fat-burning machine. The theory: Your body's go-to source of fuel is carbs. If you don't provide it with that fuel, but still force it to move, it has no choice but to turn to plan B: Burning body fat to fuel the muscles and every other physiological system.

For anyone who exercises for the sole purpose of incinerating fat, this fasting thing seems like a ~brilliant~ idea. The problem: The science behind it is merely theoretical, according to Schoenfeld. And while research suggests the body burns less fat when there are carbs in your system, there's no proof that exercising when your stomach's empty can actually change your body composition over time, mostly because studies tend to focus on the increase in fat burn during exercise, completely ignoring the body's response throughout the other 23-plus hours of the day, Schoenfeld notes. So while that writer who runs through her hunger may burn a bit more fat than a woman who runs off the calories she ate at breakfast, fasting may not change one's body composition much at all — especially if fasting works up an appetite that triggers poor eating decisions throughout the day.

Even if you eat like a kale-loving saint after fasting cardio, you may not see any visual improvements in the way your body looks, according to Schoenfeld, who adds that it's unclear where the extra fat you may burn during fasting cardio comes from. "A lot of it," he says, "is likely fat in your muscles, which has no affect on appearance."

But not everyone who exercises goes through the motions just to improve their looks. Schoenfeld suggests that ultra-endurance athletes may enjoy some long-term effects of fasting before workouts, which could train their bodies to build up certain enzymes that help burn fat more efficiently during races. Otherwise, fasting cardio can stunt performance in anyone hoping to increase speed or strength, mostly because the average person's body has to work extra hard to burn fat, compared to carbs. This leaves you with less energy to for actual exercise. Some theories suggest that fasting cardio may even lead the body to metabolize muscle itself, according to Schoenfeld​, which kind of defeats the purpose of conditioning in the first place — and makes breakfast look a whole lot better.

Diabetics and anyone with hypoglycemia or other health issues should probably forget about fasting, or at least consult a doctor before forgoing breakfast; Fasting before intense activity can make some people feel faint, Schoenfeld notes — and it can feed into disordered eating habits, in certain circumstances.

The bottom line is that fasting cardio isn't the godsend it's sometimes made out to be — and it's really not for everyone (or anyone who likes to eat and exercise. So sue me!) That said, no shade if you'd rather run (or swim, or cycle) before you eat in the a.m. Lots of people say exercising on a full stomach makes them feel sick, anyway. Just be sure to refuel after your workout — and whenever you're hungry, really.

Credit: Cosmopolitan
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