People do have a natural weight, and a fraction of people are genetically predisposed to be overweight regardless of lifestyle. But what I find impossible to accept is that somehow that number has mushroomed in the past half-century and particularly in the U.S.
I've lived and/or worked on every continent over the past 40 years, and nowhere have I seen the degree of obesity that is commonplace in the U.S. (I have not been to the Pacific Islands--I know they have the highest obesity rates there for reasons I haven't researched, but they're also a very small population). Anecdotes aside, the obesite rate in the US is nearly twice as high as some European countries (and not because people in those countries are malnourished).
It's pretty clearly the food. Living in other countries I never had to worry about weight, but as soon as I moved to the U.S. I started gaining weight right away even though I eat quite healthy. It's just very very hard to escape processed foods in the U.S. unless you 1) have money to buy more expensive food, and 2) are very conscious about it and make considerably effort to stick to fresh fruits, veggies, rice, fish, etc., no fast food, sodas, packaged foods, etc. etc.
It's also well documented that obesity is correlated with income, and it's not hard to see why, when the grocery options in low-income areas have very little healthy, minimally-processed food. Nutritional inequality is a huge issue and there's very little action taken about it. Just think about how cheap and easy it is to get unlimited refills of soda -- with a soda fountain nearly everywhere you go, compared to eating fresh food. Many people have neither the time nor money to eat healthy, and despite "be healthy" slogans, etc., nearly everything around us conspires against eating healthy (unless you have lots of $).
I'm happy that obesity-reduction pills are coming on the market because some people are naturally predisposed to gaining weight and will be helped greatly by the pills. But what I hope doesn't happen (but already see happening) is that being used to paper-over this huge problem of nutritional inequality that is the root cause of much (though not all) of the obesity in the U.S. at least.