Comment by boublepop | Hacker News Reader

Comment by boublepop | Hacker News Reader

> And, yes, you need to exercise to stay healthy, but you shouldn’t expect to see big changes on the bathroom scale with that.

Anecdotally and n=1, but I highly doubt this assertion. I lost significant weight without a diet change going from little exercise to swimming 2km 5 times per week.

I think what give people the impression of exercise not affecting the scale is that a little exercise won’t show. If you do yoga once per week, you might have the mindset of “I’m active, I do yoga, why aren’t I losing weight?” But it’s just not that much when you calculate the calories. Even at 10km of swimming a week, it’s not like I was shredding the weight instantly. I was maybe losing a bit more than 500g per week, which isn’t even significant enough to show if you aren’t consistent about weighing at the same hydration level, but over a couple of months and staying at that level it definitely shows. Now in comparison most others I know who casually swim would do maybe 400m once a week at a comfortable pace. That’s enough that you answer in a question are that “yes, I’m active, I swim each week” but not enough that you’ll significantly change your weight from it.

I think the saying shouldn’t be “you can’t outrun a bad diet” should really just be “you have to run a hell of a lot more than you think to outrun a bad diet”

Yes I agree - run 100k a week and your diet matters a lot less than if you do 3 x 5k runs a week, even though most would consider the latter to be a runner and regular exerciser.

But, run 100k a week for 10 years, and you may not need many more calories to keep it up than the 3x weekly jogger, because your body has adapted. I guess that is what the study in the article is observing.

A side note: we change our diets automatically when we start or stop exercise routines (usually) We're pretty damn good at maintaining homeostasis, so you probably did alter your diet a bit unconsciously

Assuming a 150lb person it takes an hour of moderate swimming to burn 400 calories.

That's just the energy used for the exercise itself, it doesn't count the extra calories needed for your cells to repair themselves. Powering the machinery of repair takes energy and raw materials. Those extra raw materials (protein, fats, and carbohydrates) are taken from normal diet leaving the body in more of a deficit, which feeding behavior usually corrects for by increasing intake

I mean obviously I wasn’t doing moderate swimming, I was fighting for the top places in swim.com at the pools I was swimming in, and the number is low, and my weight is different but let’s use it and show my point. Assuming 3500 kcal per lb of fat and ignoring all other details.

If you do 1h a week for half a year you are potentially at about 3 Lb or 2% body mass loss.

If you however you do 2h each weekday you are close to a potential loss of 30 Lb or 20% of weight.

Now obviously you could argue that the first case won’t work to lose weight and that you’ll just subconsciously eat a bit more to offset it, and the outcome isn’t even that large to begin with and would disappear in fluctuations of your weight unless you are consistent about hydration levels and food intake prior to stepping on the scale. But in the second case you will definitely end up changing your weight even without changes to your diet.

I was doing meal prep both before and after, so I can attest to the fact that I didn’t change my diet down to the g amount of skyr I was eating at lunch. So no, I didn’t subconsciously change my diet.

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