Don’t fast before going fast: Eating and exercise

I get this question all the time in my clinics: Is it better to work out on an empty stomach or to eat before a workout? Although you might feel more comfortable working out with nothing in your tank, that’s a terrible idea for your metabolism, especially if you’re trying to lose weight. I like to say “Don’t go fast before going fast!”


Here’s why eating before a workout is so important: When you give your metabolism plenty of fuel to burn, your thyroid produces a hormone called T3. T3 promotes fat burning. If your body is running short on fuel, your thyroid produces a different hormone called reverse T3, or RT3. This hormone makes the rounds, telling your cells that they’d better slow down and hold onto some of that fuel for later use. There’s no telling when the next shipment is coming in!

So when you work out on an empty tank, your body has to get the energy from somewhere. It’s not going to touch stored fat—that’s the last-ditch emergency stash it’s just been told to hold onto—so it ends up nibbling on your muscles instead. Ask your body for more and it’ll respond… by taking a big old bite out of your muscles to get the energy it needs. You want to burn fat, not muscle!

Prep for takeoff

Whether you’re exercising or not, it’s important to eat something nutritious within half an hour of waking up. That’s because it’s not fair to ask your body to do everything in a day–all the walking, standing, sitting, moving, even the thinking–with zero fuel in its tank.

The same reasoning applies to exercise. All you have to do is eat a piece of fresh fruit half an hour before you work out. That tells your body, “Okay, we’ve got plenty of fuel here. You can go ahead and tap that emergency supply you’ve been keeping on my thighs!”

Eating before exercise is always important, but if you are following the Fast Metabolism Diet, it’s critical. If you don’t want to eat your full breakfast for working out, you can swap your mid-morning snack for breakfast, then eat breakfast later. Just by eating a piece of fruit before your run or Zumba class, your body will burn more fat.  You may need to experiment to find out which pre-workout snack most agrees with you. The trick is to find what feels right to you while making sure your body’s fuel supply never runs empty again.

After landing

It’s also important to re-up your body’s fuel stores after a workout. The best post-workout snack is something containing about 8 grams of protein. Protein has been shown to aid muscle recovery. A big handful of almonds or walnuts works well. Or try a couple of pieces of turkey wrapped around a few celery sticks or carrots. If you are following my Fast Metabolism Diet, just be sure to eat breakfast (or your snack) at the right time. No skipping!