I have been obese for more than a decade, during which I have made many failed attempts of losing weight.
Because of the many failures, I was pretty convinced that what you say is true and no matter what I do I cannot lose weight.
Nevertheless, eventually I have made one more attempt, which was successful, so after about ten months I have reached a weight of only 2/3 of the weight that I had previously.
Then, after learning thus how to control my weight, I have kept it constant for more than a decade, until today. Losing weight was a rather unpleasant experience, especially in the beginning, but then the improvements in my quality of life have been so noticeable that the effort has certainly been worthwhile.
Looking back at time when I was obese, I regret a lot that I did not lose weight earlier and I consider that my failed attempts of losing weight had been quite stupid, because I should have realized that I am not doing all that is necessary for success.
The final attempt that was successful started with a way to measure accurately my changes in weight from a day to another, to determine the effect of the changes in diet, and it required a complete change both in what I was eating and in how I was eating.
Now it is very obvious for me why all my early attempts were not successful, because they were doomed from the start, since I was not doing them in the right way. However at that time, I was not aware of this and I did not think enough about the manner in which I should handle this problem.
After my own experience, I find it very hard to believe in the theories that for many or most obese people there are objective reasons for them to be obese instead of the fact that they have just never been taught what to eat and how to eat in order to preserve their health (in a detailed, practical way, not with generalities like "do not eat too much").
Both my grandfather and my father had been obese and they both had diabetes in old age, so I certainly did not have any help from genetic inheritance. It is enough for me to eat during a single day like I was eating when I was obese, to gain enough weight that I would need at least a week to lose it again.
The only thing with which I agree is that for poor people who are obese it is extremely difficult to lose weight, because all their time is occupied with ensuring their subsistence, so it is hard for them to reserve time for things like cooking at home, learning about how to compose a healthy diet, doing some physical exercises and so on.