Surprising Benefits of Exercising on Empty

Train on an empty tank to boost your fuel efficiencyTrain on an empty tank to boost your fuel efficiencyIt's an indisputable fact that to workout long and fast, you need to start out fully fueled. But during their prep for the Toronto Waterfront Marathon last fall, elite Canadian runners Reid Coolsaet and Eric Gillis adopted an unconventional approach: They performed some of their runs on empty tanks. It's the nutritional equivalent of training with a weighted vest; running on fumes forces your body to work harder and teaches it to burn carbs more efficiently when you workout with ample reserves.

Carbohydrates are your body's most readily available fuel source, but only a limited amount can be stored--enough to last for about 90 minutes of intense exercise--mostly in the muscles and liver. Researchers have found that exercising in a carb-depleted state helps the muscles adapt to burning more fat and boosts your body's capacity for stored carbohydrate by as much as 50 percent. Whether all this translates to better fitness is unclear, but for Coolsaet and Gillis, the evidence was compelling enough to give it a try. After working with physiologist Trent Stellingwerff, Ph.D., of the Canadian Sport Centre-Pacific, they ran personal bests of 2:10:55 and 2:11:27 in Toronto, and qualified for the Olympic Marathon in London. Here's how you can experiment with working out on an empty stomach.

Follow These 10 Rules for Fast Weight Loss

Drain the tank
One way to fully empty stored carbohydrate from your muscles is to do a hard workout in the morning followed by an afternoon workout, without refilling your carb stores between. That's a challenging and unpleasant approach. A more accessible tactic is to workout before breakfast, after an overnight fast of 10 or more hours. That approach is much less extreme but still spurs the desired changes in your body.

Stay out there While it's a good starting point, doing a 30-minute jog before breakfast won't accomplish anything, Stellingwerff cautions. It takes about an hour of fasted activity to initiate fat burning. Aim to build up over a month to at least an hour.

Best Post-Workout Power Breakfasts

Restock your store Once you've finished a fasted workout, refuel immediately to hasten recovery and build strength. Aim for 15 to 25 grams of protein and 60 to 100 grams of carbohydrate, depending on your size and the intensity of your workout. Monitor your recovery carefully before increasing the length of these workouts, and go easy the day after.

Train low, race high Fasted training isn't something to use all the time--you can't run as fast on empty, so it's harder to develop speed. If you're an athlete training for a deadline, gradually incorporate fasted runs into your schedule; do your longest and hardest "on E" runs during the heaviest training block, then scale them back as you approach the event. On event day, your carb stores should be stocked: they should last longer than usual.

Foods That Fuel Post-Workout Recovery

TELL US: Do you usually fuel up before or after a workout?

--By Alex Hutchinson, Runner's World
From the July 2012 issue of Runner's World

More from Runner's World:

50 Ways to Ensure Your Weight Loss Plan Works

10 Signs to Take a Day Off From Your Workout Routine

Pre-Workout Snacks That Won't Fill You Up