You will find two different kinds of answers to your question: scientific and anecdotal.
The science on this question is developing rapidly and it pays to keep up to date on recent studies. I read
Science Daily diet and weight loss news at
https://www.sciencedaily.com/news/he...d_weight_loss/.
I recommend
The Obesity Code by Jason Fung, but you need to read it intelligently and question some things. His main teaching is that weight gain is caused by insulin and the solution is a low-carb diet with intermittent fasting.
Anecdotally, here's what happened to me. I lost 70 lbs in about two years with a huge amount of cycling (2000 miles a year) as well as walking, running, hiking, skiing, kayaking, and weight lifting PLUS a very clean lower-calorie diet with zero sugar or junk food. I maintained the loss for a couple of years. As soon as I stopped this heroic regimen and drifted back toward my previous habits, the weight returned slowly. I regained 55 lbs, became alarmed, and lost 20 again. The lessons I learned (remember, we're talking anecdotally):
(1) No, you don't reset at a lower weight such that you don't have to be so careful about diet and exercise. You need lifelong good habits that will be radically different from the society around you.
(2) After a certain point, huge amounts of exercise have no further impact on weight loss. Researchers are now saying that exercise doesn't contribute much to weight loss (maybe 10%?), so now I exercise for health and pleasure but not really for weight loss.
(3) I believe the amount of exercise I did impaired my metabolism permanently. In the beginning I lost 1 lb for each 25 miles of biking. Then it took 50 miles per lb, then 100 miles, and then I stopped losing weight from biking, meaning zero weight loss from biking for the next 1000 miles. I now exercise 4 hours a week and observe NO impact at all on my weight.
(4) The research is now pointing to intermittent fasting as the best way to lose weight. It doesn't have to be radical---I lost the recent 20 lbs by restricting eating to 9 a.m. to 6 p.m. That's actually not difficult to do. (I also cut out all sugar.)
(5) My hardest lesson was that inhuman amounts of exercise (= surpassing what the human body was built for) will come back to haunt you not just with a slowed metabolism, but damaged joints that will one day prevent you from doing even minimal exercise to stay healthy. I lost a whole decade in pain while my body was in decline but too young to get joints replaced, according to doctors. During that decade I went from super fit and normal weight to walking with a cane, difficulty getting dressed (shoulder damage), and overweight again. Two joint replacements later, I'm functional again and can do enough exercise to be healthy, but I'll never be able to return to high-level activities. Skiing is finished, weight lifting is only to maintain not gain muscle, biking is for cardio fitness and enjoyment, not for high mileage.
That's my anecdotal cautionary tale. If I had it to do over again I would lose no more than 2 lbs a month, assume that dietary changes will be lifelong, and exercise only at a level that's fun and comfortable, never to pain and exhaustion.