Time Magazine said so.
Obviously the phsyics of exercise don’t suggest this. Fat? Use more calories than you take in. It seemed simple. Eat less or exercise more. Or both.
But, the times I’ve been fittest haven’t been the times I’ve been thinnest. All that extra exercise had other effects. And this is what the article latches onto. People are not simple energy-in, energy-out machines.
Time magazine discusses three effects.
1. People eat after exercise. I tend to smash the pasta after going for a surf on the internet, let alone how much I eat after going for a run. A bottle of Powerade Isotonic Wallabies Gold Rush contains 802 kilojoules. If you have one and do less than 23 minutes of jogging, you just gained weight.
A major study of 464 women divided them into groups who did 0, 1, 2 or 3 hours of exercise a week, for 6 months. There was no difference. They all lost a tiny bit of weight, even the no exercisers (probably related to the self-awareness that comes with filling in weight-loss forms).
2. Self control is in short supply. If you make yourself go running, you are, on that same day, less likely to make yourself not eat the quattro formaggi pizza. As they put it: ‘self control is like a muscle. It weakens after use.’
3. Exercise compensation. If you hit the gym, you become less likely to take the stairs or walk on your lunch break. You fat bastard.
[Disclaimer: exercise prevents heart disease, improves posture, increases mental acuity, etc. I’m absolutely not suggesting you sit around fasting and playing puzzle bobble.]
And, while I’m on my high horse, here’s another thing: I find the ‘energy used per amount of exercise’ claims confusing / misleading.
I may use 800 kJ in 23 minutes of jogging, but I would have used 230 while writing the blog, or 115 while asleep! I would think that only the additional kilojoule use is relevant to someone considering whether to go for a run to lose weight. If your options are
1) run for 23 minutes and have a powerade; or
2) spend 23 minutes perusing the many classic hits and memories in the thomas the think engine archives, and having a cup of tea;
only the latter will make you thinner!