I'm pretty sure that even somewhat hefty carfree people are way, way healthier than those people whose only exercise is to walk to the refrigerator. I'm not big myself, but I'll never forget the time I smirked at a fat woman I passed when I was running a 10k. She noticed the smirk, apparently, because she blew past me a few seconds later, and I couldn't catch her again despite my best effort. The lesson I learned from that experience is that girth is not necessarily a good predictor of fitness. The key, of course is exercise, and if you don't have a car, you're going to get a lot of it, there's no avoiding it. I'm willing to bet that very few carfree people will ever have to worry about diabetes or heart disease, regardless of their waist size.