Exercising on an empty stomach?

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  • bwogilvie
    bwogilvie Posts: 2,130 Member
    So today, I went to Zumba and bunt over 1000 calories. I didn't eat anything prior because I was in a rush. Ive heard that exercising on an empty stomach burns more fat because there are no carbs to burn.

    Is this true?

    Thanks
    Alex. :happy:

    Your liver and muscles can store 2000-2500 calories' worth of glycogen, the form in which glucose is stored for use as energy. That's plenty of carbohydrate. From what I've read, your ability to mobilize fatty acids as an energy source has more to do with training than with exercising on an empty stomach.

    How much Zumba were you doing, by the way - two hours? The Compendium of Physical Activities estimates Zumba at 6.5-7.3 METs (https://sites.google.com/site/compendiumofphysicalactivities/Activity-Categories/new-activity-updates). Subtract the one MET that you would burn just by sitting down and doing nothing, that suggests an exercise calorie burn of 5.5-6.3 calories per kg of body weight per hour, i.e. 440-504 calories/hr for someone who weighs 80 kg/176 lb./12 st. 8 lb.

    The MET estimates in the Compendium are just that - estimates - but I think they're more reliable than MFP's fitness database, which tends to overestimate calorie burn (it has 8.8 METs for Zumba). A lot of people who get frustrated and give up on MFP because they're not losing weight are being misled by overly generous exercise estimates. I went for a bike ride on Friday that burned 750 calories, according to my heart rate monitor, but MFP's database claims 1006. If I believed MFP, I would have eaten 250 calories too much.

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