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Comment by tgb | Hacker News Reader

> Exercising is almost irrelevant

I get where this is coming from, but I really feel like everyone has over-corrected on this and ended up being wrong again in the opposite direction. Exercise burns a significant number of calories. An hour run can easily burn 700 calories for someone my size (~70kg). Running an hour a day 6 days a week burns more than one pound of fat a week. I run less than that amount and my phone estimates I burned 15,000 calories last month from running. That's not a get-slim-quick magic pill, but that's really significant!

Exercising for 20 minutes once or twice a week is pretty negligible and people over-correct by eating more. But a consistent, easily-doable exercise habit is a huge source of additional "calories out".

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> An hour run can easily burn 700 calories for someone my size (~70kg).

If you can run for 1h then you are quite likely already in a good shape (if not, running 1h every day would kill your joints).

> Running an hour a day 6 days a week burns more than one pound of fat a week.

Usual advise is to run at most every other day to let the body regenerate. That said, eating 500kcal less each day has the same effect and is much easier then running 1h six days in a row.

Running (in GP's case) or exercising in general has the added benefit of building (up to a point) more muscle. More muscle mass means higher basal metabolic rate. Higher BMR means you burn more calories all the time.

So yes, a 500 kcal deficit every day (without adding exercise) is comparable in the short term to the runner burning 700 kcal extra 5 days a week (but not adjusting their diet). But, especially if that muscle mass is sustained, the runner or person engaging in regular exercise is going to be better off in the long term with respect to keeping the weight off.

Exercise and calorie reduction don't have the same effect. Running stresses the body which promotes muscle growth and reduces resting heart rate (among lots of other physical benefits). Calorie restriction forces to body to fill an energy deficit, usually by burning fat but potentially also muscle mass.

But running (compared to sprinting or weight exercises) is not exactly good at building up muscles.

Exercising does only one thing for weight loss: it builds up your muscle mass. Muscles have higher 'passive' calorie burn than fat tissue. Thus, you can take in more calories without adding weight, and if you eat the same as before adding muscles, you'll lose weight faster.

Why do you say that? I mean, I just pointed out it burns me 15000 calories a month and frankly I haven't built any muscle from running.

I read a paper recently that showed we tend to offset exercise with lethargy elsewhere without even being conscious of it. Anecdotally this seems true as I'm currently sat on the sofa following a thirty mile bike ride this morning.

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