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Comment by nradov | Hacker News Reader

I can't read the full article, but the abstract didn't mention anything about the effects of the caloric restriction protocol on the muscle mass of human subjects. This is why I'm very skeptical that it will actually work to extend human lifespans. We know that sarcopenia increases the risk of serious falls for elderly people. And any physician can tell you how a bad fall frequently causes loss of mobility, and sets off a chain of physical declines leading to death in a couple years.

So personally I'm going to contine eating a lot of calories, and doing a lot of hard exercise. Maybe I'll age faster but at least I won't be frail.

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It says caloric restriction without malnutrition. Eating 15% less carb and fat calories won't make you loose any more muscle mass than you would have otherwise.

But I am wondering my self too, what's the effect when you combine CR with exercise. 15% out of 2000 calories is 300 cal or about 30 mins jogging. So instead of eating less, will the effect be similar if I spend 300 cal more everyday through exercise?

Malnutrition is a vague term that can mean many different things. You can lose significant muscle mass even if you aren't technically malnourished.

You absolutely can lose muscle mass if you cut carb and fat calories below a certain threshold. Whether that threshold is above or below 15% depends on many factors. The Real Science of Sport podcast has a good explanation of how this works.

https://play.acast.com/s/f3fb5c75-b943-4f5d-bd87-27c91611dd2...

There was a thread last week https://news.ycombinator.com/item?id=30381000 that discussed scientist(s) doing studies that debunk the theory that burning more calories during exercise leads to weight loss - your body compensates by burning fewer calories at rest so the daily calorie budget your body needs stays more or less constant for vast majority (possibly all) of people and exercise/diet combinations.

> effects of the caloric restriction protocol on the muscle mass of human subjects

Some think it's a myth. It makes sense if you think about it, the body uses a lot of energy and resources to build muscle (and tendons, and to mineralize bones) only to destroy it right away at the first intake dip, not even considering the primary source for energy storage, which is fat?

Caloric restriction burns A LOT of fat. It's why it's there in the first place.

https://www.dietdoctor.com/does-fasting-burn-muscle

Here's a meta-analysis with some actual data from researchers: https://www.jscimedcentral.com/SportsMedicine/sportsmedicine...

The research seems to show that if you're trying to be muscular, CR is probably not going to help you. However, CR actually has some positive effects on exercise performance and outcomes for activities that don't revolve around raw strength. Unfortunately, there's very little research on CR vs. strength training in people who are not elderly and not overweight. I share your frustration there - so much of the hype around CR comes from it being an easy solution for people who are not already physically fit.

I don't think calorie restriction will lead to you breaking your hip because you are so emaciated. I think the current status of fitness (going to the gym and lifting weights then eating a bunch of protein) is a totally backward approach to health and exercise. If you want to be muscular for aesthetic reasons that is totally valid, but it is misleading to pretend it is healthy.

This is coming from someone who did tons of hard exercise from 16-26 then completely reworked my approach from intensity to volume, started restricting calories and reduced protein intake. That said fitness is a journey and you should always be willing to completely reverse everything you think you know.

I think you will be fine unless you are over trained. As long as your cico is balanced, I don't think there is anything wrong with that.

cico?

calories in, calories out

Counting calories in, calories out.

You won’t age faster. The exercise will train your body to become more resistant to oxidation and you will delay morbidity right up until the day you actually die.

Cartilage wear and tear is the only thing that will really slow you down and put you on a spiral of being unable to exercise effectively and thus getting frailer. But maybe we will discover ways to regrow cartilage.

I’d say the fasting method is just another alternative for people to combat aging if they don’t feel like working out, but you can’t mix the two methods. Choose one path or the other.

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