Very long term, energy burned will be == energy taken in. If that's consistently out of balance by... say 100 Kcal/day, that's 0.2 lb/week every week or 10 lb/year or 100 lb/decade. How many 50-year-olds do you know who are 300 pounds heavier (or lighter) than they were at 20?
Not really, unless we're counting death. Most people gain weight as they get older.
> If that's consistently out of balance by... say 100 Kcal/day, that's 0.2 lb/week every week or 10 lb/year or 100 lb/decade. How many 50-year-olds do you know who are 300 pounds heavier (or lighter) than they were at 20?
You're phrasing that the wrong way. Your BMR changes depending on your current weight. If you weigh 180 pounds at 20 and you eat 2700 calories a day, eventually you'll reach a point where 2700 calories is what you require to maintain your body weight (probably somewhere in the 220-240 lb range).
To gain 300 pounds over 30 years would require you to constantly be consuming more and more as time goes on.
You're also completely negating the fact that most people would (and probably do) have a 'reality check' once they get into the 200+ range, and reduce their caloric intake (though unfortunately most likely only to resume their high caloric intake once they've dropped in weight a little).
You're agreeing with the post then, that very long term it's pretty even.
Originally I thought the poster meant "it can't be that simple because otherwise everyone would be 500 pounds", but yes, over time it does become true.