I have noticed that the generation born during and shortly after the war in Poland, which had far greater shortages than UK or US, tend to be significantly shorter than those born later and much shorter-lived than those born in the 20s and 30s. I can think of various wartime and post-war effects that may have caused this, but AFAIK there's been no study into it.
Cycling, I think, has great physical and mental health benefits which far exceed its role in reducing overweight, however good or bad it may be at that.