The Benefits Of Running On Empty

It's an indisputable fact that to run far 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 race 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. (So how should you fuel up before a big race or workout? Learn the Right Way to Carbo-Load.)

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Researchers have found that training 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 faster race times 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 to experiment with running on empty.

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 run, without refilling your carb stores between workouts. That's a challenging and un-pleasant approach (and it can lead to complications—read the Dangers of Running on Empty to learn what you should avoid). A more accessible tactic is to run 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.

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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 running to initiate fat burning. Stellingwerff suggests that elite marathoners running more than 100 miles a week build their fasted runs to two hours, spending half that time at tempo pace. For everyone else, aim to build up over a month to at least an hour.

MoreWhere to Go From Here: Building the Miles

Restock Your Store

Once you've finished a fasted run, 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 run. Monitor your recovery carefully before increasing the length of these workouts, and run easy the day after. Try these Best Foods for Post-Race Recovery to rebuild your strength.

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