I'm not sure why you would want to restrict calories in your case? Even if the work on fasting from animal models carries over to humans beyond the benefits of reducing metabolic syndrome (which is unclear), being underweight is definitely a risk factor for all cause mortality.

If anything it kinda sounds like your natural 'set point' already has you calorie restricted insofar as it would.be beneficial

Well, at this height, are you not calorie-restricted already?

Depends on the activity level. According to this calculator:

https://www.calculator.net/bmr-calculator.html

his (assuming a dude) energy expenditure is:

Basal metabolic rate: 1819 cal/day

Sedentary (little or no exercise) 2,183

Exercise 1-3 times/week 2,501

If he is in the "little or no exercise" category, he should aim to get into "Exercise" category. Exercise (in reasonable amount) is healthy whether you loose weight or not.

He should not be aiming for "basal metabolic rate".

So does caloric restriction in general just mean maintaining a low-ish BMI?

For an animal model I imagine it means being fed less than would have been eaten ad libidum, or less than was eaten by a pair fed individual.

But considering you are probably in like the <= 3rd percentile of healthy humans in terms of BMI, your 'normal' calories are pretty damn low and probably commensurate with what would be considered calorie restricted.

So if I'm eating more and gaining lean muscle, I could still fall under the calorie-restricted category?

Basically I don't enjoy being thin but I do want to live to 120. I already do calisthenics and basketball regularly, just wondering what else I could do to min-max my longevity.

I don't think mechanism is worked out well enough to say for sure that being calorie restricted for someone like you that already is lean and not at risk of obesity related disease would be beneficial.

My first guess would be that even if there are longevity benefits for calorie restriction, depending what the mechanism is, you could either be already enjoying them by virtue of clearly not eating that much relative to your lifestyle and metabolism, or alternatively that any benefits of starving yourself enough to clamp down on mToR or some other hypothesised mechanism may well be counterproductive by pushing you close to malnutrition or just increasing your risk of injury or whatever.

I guess you could do a self experiment if you were really interested, try a fasting mimicking diet regimen where its five days a month every month to get the benefits of calorie restriction, and see if you can maintain lean mass while getting improvement in markers.

> just wondering what else I could do to min-max my longevity

Stay indoors, don't engage in medium to high risk activity, invest all your money into aging research.

Don’t drink alcohol and stay out of cars.

I think you should think about it as consuming less energy than your body needs everyday.

This specific commenter could be considered too light for his frame. 165lbs is only 75kg. If anything, eat more and put on muscle.

drop 800 calories and watch your weight for a month, you should be able to get a pretty good idea how much.