Thread by @Mangan150

I don't advocate that humans practice calorie restriction (CR).

So why do I discuss CR so much?

Because it is a proof of principle.

CR is the most robust and reliable way to extend lifespan of lab animals.

That says some important things about aging.

For one, it goes against a widely held scientific tenet of aging.

That tenet says that aging occurs because organisms lack the resources to fully repair themselves.

They repair themselves "just enough" but concentrate resources on where it really counts: sex and reproduction.

Yet when you give animals more resources - food - they die younger.

When you give them less food, they instead repair themselves *better* and live *longer*.

Therefore the reason aging exists cannot be because we don't use resources to stay youthful.

In any case, CR has its own set of problems, and humans that practice it report being cold, and having low energy and low libido.

Doesn't seem too pleasant.

Not to mention possibly the biggest drawback: you must have an iron will to withstand hunger. Few do.

Intermittent fasting looks like it has the advantages of CR without the drawbacks.

With fasting, you don't even necessarily have a lower calorie intake, just different timing.

With intermittent fasting, you get the robust increase in cellular defense and repair mechanisms, but without the considerable drawbacks of lifelong calorie restriction.

Much of the effects of CR, and possibly intermittent fasting, may be simply due to carbohydrate restriction, which means that a ketogenic diet may do much the same.

Ketones do extend lifespan in lab animals.

And, while theres a lot of scientific debate on why CR and fasting extend lifespan, much of it may be due to production of ketones and a low insulin level.

CR illustrates another proof of principle: there's an inverse relationship between growth and/or size, and lifespan.

Big animals (within species) die younger. Humans too.

The world's longest lived human, Jeanne Calment, was 4'8" and 85 lbs at the time of her death at 122.

Robert Marchand, the celebrated 105-year-old Frenchman who keeps setting cycling records, is 5'0" and 115 lbs.

Centenarians are generally small.

nytimes.com/2017/02/08/wel…

So, does adding muscle, which makes you bigger, shorten lifespan?

This is speculative, but my answer is: yes and no.

If you add muscle to your genetic limits, using no drugs and without overtraining, that will extend your lifespan.

More muscle is robustly associated with less chronic disease and lower mortality rates.

But if you add muscle using drugs, and daily hard training, like a pro bodybuilder, yes, that's likely to shorten your lifespan.

Anabolic steroids are growth-promoting, so according to theory, that alone would shorten lifespan.

Excessive exercise is on the wrong side of the J-curve of hormesis, and into the toxic zone.

What constitutes excessive exercise isn't easily determined though.

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