Yes, exactly. Epigenetics. If you've got the genes tucked away to become obese under certain conditions and those conditions show up, they'll trigger those genes to express themselves and you'll become obese whereas under other non-triggering conditions you might not have. Today's high carbohydrate low fat sugar and chemical-laced environment seems to be a pretty potent trigger. I've been reflecting lately on how far removed from a natural human environment those of us in first world nations are. Strange highly processed edible things we call "food" instead of stuff that was recently living unmodified out in nature, artificial light sources plus blue light from devices that mess with our circadian rhythm, lack of natural sunlight because we're stuck indoors all day at work or school or fear the sun and slather on chemical-filled sunscreens, all sorts of other odd chemicals in our personal care/cleaning products, the buildings we live in, etc. Really strange foreign environment for human beings to be living compared with the natural environment out there that humans were built to genetically expect and thrive in. I really like a lot of what technology offers us and don't plan to give it up, but I think it's good to be aware I wasn't designed to exist in a completely climate-controlled neutral temperature without daily sun, little movement, light all night, weird processed chemicals and foods, etc. and to take whatever steps I find reasonable to offset the negatives: better food, exercise, sunlight, heat/cold exposure, selectivity in product purchases, minimize the blue in electronic screens at night, etc.