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Exercise has nothing to do with weight loss. Caloric restriction also doesn't work without consuming the correct fats to satiate your appetite. As you age there is no amount of exercise that will allow you to maintain the amount you weigh in you 20's or 30's. It will all depend on your diet of the correct foods. I would suggest probably the best book ever written about why people get fat. Why We Get Fat: And What to…
"As you age there is no amount of exercise that will allow you to maintain the amount you weigh in you 20's or 30's." This seems overly general and anecdotally total BS. I still eat what I like just like I did in my 20s/30s. It's just that what I like is generally lots of vegetables and sufficient protein, with occasional vices slipped in because YOLO(tm). That said, without the exercise, I gain about a pound per wee…
Here is an excerpt from the book I mentioned.
Why We Get Fat: And What to Do About It by Gary Taubes
>The authors were Paul Williams, a statistics expert at the Lawrence Berkeley National Laboratory in Berkeley, California, and Peter Wood, a Stanford University researcher who has been studying the effect of exercise on health since the 1970s. Williams and Wood collected detailed information on almost thirteen thousand habitual runners (all subscribers to Runner’s World magazine) and then compared the weekly mileage of these runners with how much they weighed from year to year. Those who ran the most tended to weigh the least, but all these runners tended to get fatter with each passing year, even those who ran more than forty miles a week—eight miles a day, say, five days a week.
This observation led Williams and Wood, both believers in the doctrine of calories-in/calories-out, to suggest that even the most dedicated runners had to increase their distance by a few miles a week, year after year—expend even more energy as they got older—if they wanted to remain lean. If men added two miles to their weekly distance every year, and women three, according to Williams and Wood, then they might manage to remain lean, because this might mean expending in running the calories that they seemed fated otherwise to accumulate as fat.
Let’s see where that logic takes us. Imagine a man in his twenties who runs twenty miles a week—say, four miles a day, five days a week. According to Williams and Wood (and the logic and mathematics of calories-in/calories-out), he will have to double that in his thirties (eight miles a day, five days a week) and triple it in his forties (twelve miles a day, five days a week) to keep fat from accumulating. A woman in her twenties who runs three miles a day, five times a week—an impressive but not excessive amount—would have to up her daily distance to fifteen miles in her forties to retain her youthful figure. If she does eight-minute miles, a nice pace for such a distance, she’d better be prepared to spend two hours on each of her running days to keep her weight in check.