How exactly can your body adjust that much though? There is some minimum baseline level of calorie burn to stay alive and keep your body temp etc.

If you workout enough calories that exceeds the minimum baseline to keep you alive, the body can't adapt below that or adapt into the negative.

For a 200 lb man, jogging for 2 hours burns like 2000 calories, so that's 12,000 a week for 6 times a week.

What's the lowest a body will adapt to slow it's baseline metabolic rate? I am reading that the BMR can only reduce by like maybe 15-20% due to body adaptation.

This would put their baseline calorie burn at around 1500, and then if they are burning ~1700 a day from their jogging, they can eat 3200 a day to maintain or 3000 to even slowly lose weight over time, which is a decent amount that you can have a pretty fun "diet" of what you consume IMO.

> For a 200 lb man, jogging for 2 hours burns like 2000 calories

ogging a mile will burn around 100kcal, a bit more if you're decently overweight, let's be generous and say 150kcal. Someone who isn't in good shape and is overweight (the kind of person we're likely talking about) isn't going to be running that fast, maybe 3mph. So that's 6 miles in 2 hours. Even if I'm incredibly generous and say they'll burn 200kcal/mi, that's only 1200kcal. But in reality it's probably more like 900kcal.

But let's be real here. Your average (even above-average) overweight person with a not-so-great diet is not going to be jogging for 2 hours. Maybe they'll jog for an hour. So 450-600kcal. And maybe they'll do that 2-3 times a week.

1350-1800kcal extra burned every week is great! Except that still probably won't be what happens, exactly. Unless this person is also counting calories, or consciously working hard to keep their exact same diet, they will probably unconsciously eat more. Adding a 9mi/week jogging regimen to your life, especially if you're overweight, is going to make you more hungry than usual, so you will eat more. How much? Well, hard to say. Maybe enough so that you still end up with a calorie deficit, but in many (most, I'd guess) cases you'll still have a surplus, even if less than before.

This is all still a good thing! A 500kcal surplus per week when you're running 9 miles is much better than a 1500kcal surplus every week with no exercise. But this (hopefully) demonstrates that it's not as simple as "I'll just add some exercise and that'll get my weight under control". You need to change your diet, and take in fewer calories. It's hard. But it's the only way -- for the vast majority of people -- that this will work.

For a 200 lb man, just jogging doesn't burn 1000 kcal/hr. You have to actually run at a pace of about 8:30 min/mi. People who can sustain that for 2 hours per day every day are not overweight in the first place.