The Wordsmith's Forge

I've read up a lot on this, as one of those people who did make a lot of dietary and lifestyle changes and dropped my weight by 25% and have kept it off for six years now, and I remember reading that even lab animals on controlled diets have higher weights now than they did decades ago, so some kind of environmental factor seems highly likely. As to what it is, well, we didn't know the chemical process for why people felt hungry until relatively recently, so I suspect narrowing it down will take a long time.