Aerobic Exercise Makes You Fat

In General, Movement by Mikki Reilly3 Comments

I was recently contacted by a client I trained a few years back who said she’s been doing steady-state aerobic exercise everyday for 40 minutes (skating along the bike trail by the beach) and that she’s beginning to gain weight.

How could this be since aerobic exercise burns calories? Athlete/scientist, Art De Vany theorizes that too much aerobic exercise increases stress hormones, which leads to overeating, and decreases the hormone which tells your body to burn fat and build muscle: growth hormone.

High volume aerobic training also converts your fast twitch muscle fibers into intermediate and slow twitch muscle fibers. And, it decreases your total muscle mass, which slows down your metabolic rate, so you expend less energy, at rest.

Obviously, it takes a while for this to happen. And you’d certainly burn some fat in the beginning. But if fat loss is your goal, a fitness program that includes both interval training and weight lifting would be so much more effective.

I’d love to hear your comments…


  1. Whenever I hear this sort of provocative result, I have to wonder why it goes against the prevailing wisdom. I’m assuming the key here is ‘too much aerobic exercise’ and ‘high volume aerobic training’, and that getting out and walking 30 minutes a day has a clear benefit for initial weight loss. At some point the daily marathon provides diminishing returns, but when does a change to intervals make sense?
    I’m enjoying the blog and look forward to more. I’ll go run stadiums now …

  2. Interesting and, as Alan said, provocative. It depends on what you want to accomplish with your exercise regime. Training for burning fat and training for building cardiovascular endurance aren’t the same, but I think sometimes we hope that one kind of exercise will meet all our needs. This is obviously not true. Now I’m off to check out Alan and Harriet’s blog!

  3. Thanks for your comments, Alan and Lisa. It’s true that the 30 minutes of low intensity exercise burns fat for the sedentary individual. But too much of a good thing can have negative consequences. Its one of the many paradoxes of fitness training and body composition.

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