There are many reasons to be obese, that don't include consumption of "junk food", like having a hormonal disbalance. Some people are simply predisposed to gain fat from seemingly "safe" foods.
Potatoes, rice, bananas, processed grains, etc. are natural fat gainers for many people.
There are, indeed, people who have medical conditions that can lead to weight gain. The most common of these are medical conditions that limit physical activity. There are also hormonal issues that can lead to overeating, but it's more PC to say hormonal issues lead to magical weight gain.
The fact is you and every human have basal metabolic rate. This is the number of kcals that your body burns when you're doing nothing. You can have it easily measured. You can then monitor activity to determine additional kcals burned by walking, gardening, exercise, etc. and arrive at a reasonable estimate for the average kcals burned per day.
I defy you to explain any reason why someone who consumes at that level can put on weight. It either means their body somehow generates energy from items that are undigested by "normal" humans or that certain foods magically suppress their metabolic system (make a pill out of that and we can end starvation!).
The fact is that many "hormone" problems, such as insulin resistance, are circular. Diet - mainly high fat and high simple-sugar diets - are the biggest controllable risk factor. Insulin resistance, in particular, becomes a feedback problem: high bodyfat increases insulin resistance which increases appetite Either way, for the vast majority of these issues are best controlled with *exercise* and, in some cases, low-glycemic-index diets. NOTE this is not the same as low-carb since most diabetes/insulin resistance diets are geared towards lots of vegetables, not some Atkins quackery of eating bacon and butter sandwiches.
Again the common element in all solutions is exercise.
