I'm 5'11" and my optimal weight in top physical condition would be 145 lbs, same as when I boxed amateur in my late teens and early 20s. I grew from a string bean 132 lb lightweight to full welterweight, but when I bulked up to 155 for some light middleweight bouts I looked "fat." My body didn't change much with age so my natural weight remained around 155 for years. My dad was the same way and never became overweight, even after age and illness forced him to give up tennis and golf.
After a 2001 car wreck busted up my back and neck I was physically inactive for years, walked with a cane until 2014, and ballooned to 205 lbs. That was huge for me. My frame just can't carry that kind of weight naturally and it showed. That mostly came from junk food and beer.
After resuming cycling in 2015 and reaching peak fitness again by 2017, my weight hovered between 145-150. I looked and felt great. I still had -- and have -- a bit of a tummy pudge of loose skin from having weighed so much between 2001-2014. I like it. I don't have any visible scars despite some serious injuries, but the tummy pudge reminds me to never take for granted my diet and fitness.
After catching COVID in late 2021 my energy sagged, I developed annoying vertigo that lasted for almost a year, forcing me to quit cycling outdoors. I took up walking, then jogging, then running, as an alternative. Between less exercise and eating more junk food I gained up to 160 lbs. I'm still at 160, despite being more energized and active again. That's entirely due to a sweet tooth. And I found long distance cycling more efficient for burning fat than running. Even though I'm doing the same hours per week, month and year running, it's not as efficient as cycling, at least for me.
As long as I'm no heavier than 160, I'm satisfied with my weight. If I get serious about running as an alternative to cycling, and decide to enter more distance running events, I'll cut the junk food and sugar and drop back to 150. As long as my everyday weight is 160 without feeling like I'm sacrificing anything, it's a reasonable goal.
I know from previous experience, there's a difficult transition period in retraining the body to ignore cravings for sugar and carbs as fuel, and learn to burn fat reserves. After a few weeks the body adapts, the cravings subside, and it gets easier.
I think a key factor in weight control from diet and exercise is the "buzz" many of us get from exercise. Researchers are still trying to determine what specific brain and body chemicals produce that buzz -- over the years theories have varied from endorphins to dopamine, with a dash of serotonin and oxytocin thrown in. Whatever it is, it seems to hit the body's natural receptors identified as opioid and endocannabinoid receptors. I know my chronic pain from various injuries subside during a workout. But the pain relief is temporary and usually returns within a couple of hours after a workout. So, basically, some of us who crave that buzz from physical activities are junkies. If we don't get it from exercise, we'll go for makeshift stuff like comfort food, dope and booze, all of which are inferior substitutes.
It appears some humans never do get that buzz from exercise, so it's unrealistic to expect them to conform to our expectations.