> Don't ask me the medical reason why, maybe it's the same phenomenon as when people who haven't worked out for years start a program and quickly lose 10 pounds of water weight but then find the rest is harder to lose
It's because the body is extremely good at adapting to whatever you do to it. Even if you were riding for a hundred hours a week at maximum aerobic output, your body would slowly adapt and you would stop making gains (getting faster, losing weight).
Over a long period of exercise, you have to constantly vary what you are doing to your body so it won't adapt and plateau. Keep throwing different challenges at your body, and it will keep adapting in an attempt to deal with these new challenges.
Try sprinting home from work at max output a couple of days a week, then intentionally go for an extremely long ride on the weekend at a sustainable pace. Don't do the same thing day-in, day-out
Also, eat less calories if you want to lose weight.
Also, people struggle with weight loss because they approach it only from the side of burning excess calories with exercise, but as long as their caloric requirements stay the same, the moment they stop exercising, calories start piling up again. If you want to burn more fuel, there is longer lasting approach: grow a bigger engine. That means: gain some muscle. The more muscle you have, the more calories you will be burning, even while eating an ice-cream on a couch. Muscles will also make you look less flabby, because toned abs will keep your belly in check.
"it never gets easier, you just go faster" - Greg LeMond
this is the reason elite athletes keep getting better, they keep up intensity, continuing to push the limits. Bike committing gets easier, and, like you said, your body adjusts to the level of output you need to get to work.
It's because the body is extremely good at adapting to whatever you do to it. Even if you were riding for a hundred hours a week at maximum aerobic output, your body would slowly adapt and you would stop making gains (getting faster, losing weight).
Over a long period of exercise, you have to constantly vary what you are doing to your body so it won't adapt and plateau. Keep throwing different challenges at your body, and it will keep adapting in an attempt to deal with these new challenges.
Try sprinting home from work at max output a couple of days a week, then intentionally go for an extremely long ride on the weekend at a sustainable pace. Don't do the same thing day-in, day-out
Also, eat less calories if you want to lose weight.