Allan makes an excellent point.
In my own case, my weight crept up over the course of the past couple/few decades. At my peak I was over 280#, had a sedentary job and worked for a company that was "nice enough" to keep us well stocked with pastries a couple days a week. In hindsight, I was a complete mess -- overweight, out of shape, persistent acid reflux, the works. Since then I'd made a lot of improvement, but was still overweight and not getting enough exercise. I told myself it wasn't that bad; at least I didn't look like other guys who weighed as much as I did. My excess tonnage is pretty well distributed, so I'm not carrying a beer belly or triple chins. But the scale doesn't lie, although it may groan a little in agony.
My doctor tried putting me on Lipitor a number of years ago for high cholesterol, but I didn't like the side effects - and figured I could get to the gym, lose some weight and not need the pills. Besides, I'd had a treadmill stress test a few years ago, and the doc said my heart was in fine shape. And maybe it was... in 2004.
While in theory my approach would have worked, the fact remains I didn't get to the gym, didn't lose enough weight, and ended up last October with a heart attack. Up until a couple of days before the MI, I felt great. I was going to the gym once or twice a week (some weeks), eating fairly healthy, and down over 15# from my peak weight. I was making (very) slow but steady progress. But -- too little, too late.
Since I am left with one coronary artery that's still over 70% blocked and can't be reached with a cath/stent, my chances at getting a medical are slim to none -- ever. So now I'm screwed. I have to sell the RV7 I've worked so hard on, I have a flying club membership I have not been able to unload, and there are no options around here for LSA - so I'm faced with either quitting flying for good, or building an RV-12. I'm just not sure I can justify a $75K+ expense for day VFR only.
So don't be like me. If you've been putting off getting back in shape, don't. I'm not looking for pity, or even sympathy. I have no one to blame for this but myself. I'm here to tell you, though, that if you're living the way I was it WILL catch up with you eventually, and your flying days could end abruptly.
By the way... when the heart attack hit, I was on my way to the airport to take the club 172 out for a couple of hours and get night current again. I guess it's a good thing it didn't happen an hour later.