Personally, I've never seen obesity as a failure of character or willpower, at least as long as I can remember having any particular views on it at all. I see it as a failure of information and choices.
Obesity was rare until the United States officially decided in 1977 that saturated fats were considered harmful. A few years later, it started rising to the current epidemic level. We've come a long way since the American Heart Association was recommending candy and soda as "healthy" alternatives to real food, but the idea that an optimal diet contains low saturated fat and high complex carbohydrates remains firmly entrenched in present-day nutritional and medical orthodoxy.
Imagine a counterfactual where Congress had reached the opposite conclusion, instead recommending a standard diet full of saturated fats, high in salts (both sodium and potassium), moderate in monounsaturated fats, low in polyunsaturated fats, and sparing in carbohydrates. The population and food industry would have moved in an entirely different direction. We'd have a whole different universe of nutritional advice, diet trends, restaurant menu options, and easily available processed foods. A lot would be the same, but large sections of the grocery store would look like lowcarbfoods.com, maybe burger joints would serve mozzarella sticks instead of fries, maybe instead of potato chips and corn chips people would eat pork rinds and kale chips, and maybe instead of rice or potatoes an average dinner would include all manner of delicious fried vegetables. Instead of a low(er)-fat (i.e. high(er)-carb) diet, doctors would tell fat people to try keto. Maybe that timeline's equivalent to trans fat would be sugar alcohols and artificial sweeteners, and governments would ultimately pressure the industry to transition to stevia, monk fruit, and inulin fiber.
In such an alternate universe, I'm sure the food industry would still work overtime to find ways to make many of its products shitty and addictive, and I'm sure the average person would still lean heavily on processed foods and fast food over home cooking and whole foods. I'm sure that would cause its own set of health issues, but what I highly doubt it would cause is an obesity epidemic. It's simply a lot harder to overeat fats than it is carbs. We'd also inherently have less insulin resistance, which means less type 2 diabetes, less dementia, and probably a good amount less of mental/neurological issues like depression and anxiety.
Unfortunately, we live in this universe. And in this universe, I find it really hard to blame individuals for struggling with obesity when we've practically purpose-built an environment to make us fat and keep us that way. In order to not be fat (by pre-1980 standards), you either have to win the genetic lottery, be extraordinarily physically active, put a high amount of effort into controlling your caloric intake, or be willing to go against the grain (no pun intended) on what you've most likely been led to believe for your entire life by everyone and everything around you. It's great to fall into one of those four buckets, but on a population scale it should be obvious that the majority wouldn't.