Metabolism does slow down, but there is a lower limit. The exact numbers and rate will change, but the fact is that sufficient caloric restriction will cause weight loss.

That said, as someone who struggles with weight loss, it's still hard. There are both physioloical and psychological issues that make it challenging.

As an aside, keto is the only thing thats worked reliably for me so far - largely because of the caloric restriction it inherently forces. I stopped following it because people kept telling me they were concerned it was unhealthy, but I'm sure the weight is worse than anything else.

Keto was the only thing that worked for me too. I found it a lot easier to just pick some days and say "I'm not eating anything on these days" than it was to constantly track and procure a perfect diet day after day without lapses.

Not sure who told you it was bad for you, I've predominantly heard it being touted as beneficial and longevity-increasing.

Metabolism changes is something like going down from 2100 maintenance calories to 1900 calories. A donut is /at least/ 300+ calories. Age-related metabolism changes are also not that serious.

I've seen people losing 40kg (120kg to 80kg) by just walking and counting calories. It's the last 5-6 kg that are harder than the first 20kg is almost trivial to lose - one all the right habits are in place.

And habits are the hardest part. It's not the body, not laws of thermodynamics, it's just your habits (most of the time).

No, it's more like going from ~2500 maintenance to ~1400 cal/day before your body finally decides to start burning fat instead of lowering its metabolism further. At least for me.

Obviously different people are different.

And it has utterly nothing to do with habits, you can see my other comment. It's about the whether you can even manage the other health consequences you suffer from your metabolism being so low.

1400 a day? For an immobilised hospital patient- maybe. It's like not moving at all! How would your body compensate for it?

Given lightweight excercise (walking,kettlebells, etc) that's almost impossible!

> but the fact is that sufficient caloric restriction will cause weight loss.

Yes, but at the cost of your immune system severely degrading so you suddenly get colds all the time. At the cost of extreme fatigue and brain fog. At least that's what's made weight loss difficult for me at times.

Because for some people (like me), your body drops its metabolism to well below what's healthy before it even thinks about burning fat. It's not any question at all of willpower or psychology, it's purely physiological.

* * *

I think “for many people” is more like “for a minority of people.”

For a few people losing weight is complex. For most people, it’s simple.

Eat less. Move more.

Saying otherwise is a cop out.

Yes! Cannot stress it enough. Move. It doesn't even have to be intense! Running can be traumatic. But calories don't care if it's a walk you're doing or a run.

Unless you have some fundamental food-related disorders it's not that hard. Our bodies were meant to gain weight weight quickly - and lose it if necessary. For most people losing 10-20 kg is a question of 3-4 months, or even less.

> For most people, it’s simple.

If it were that simple, most people would be able to do it. The actual evidence shows it's far more complex than you think.

There's no cop out here. Many people's bodies simply refuse to burn fat until their metabolism has gone so low it has other dangerous health consequences.

Also, as for "move more", the evidence shows that people generally eat even more after exercise to compensate. Exercise is great for general health, but it's a terrible strategy for most people for losing weight. It simply backfires.