I'm going to have to slightly disagree with some pp about 'we are all obese' because of what you ate regardless of why it happened. Perhaps we're saying the same thing here or not but I'm going to try to explain a little bit about some people's* *reason for being obese.
A family with 3 children - 2 girls and a boy - and only 1 child is obese. They're fed the same things, they did the same activities, went to the same schools but something in her body stores more fat and/or is unable to burn as much fat as her siblings. They're adults now and it's the same thing. Mother is the other one who's obese and she exercises, eats healthy and not too many calories most times. It is likely something in her genes passed on to one of her children. Her poor daughter, Lady A, has tried everything as an adult to lose weight including going to the dentist and getting her teeth wired shut so she could only have liquids! Once she stopped, the weight built back up again.
Another woman, Lady B, who's been skinny her whole life suddenly has health issues that has caused her to need to take tons of different medications, some of which are known to cause weight gain as side effects. She comes from a family where no one is obese. She has ARFID too so her meals are quite limited and restricted, making staying slim even easier. She rarely eats too much. On taking these medication, she has ballooned within 2 years. She still has ARFID so her meals haven't changed. The only thing that has changed is her body's metabolism and insulin resistance. Something in her body now seems to store fat twice or 3 times or more than normal and/or doesn't break down fat as much as it's supposed to. So every single calorie, every single fat in food, every single carb becomes a source of extra fat storage and impossible to burn despite her exercising after she got better health wise. Her weight wouldn't budge. She lowered her already low calories just to lose weight and all she could lose was 2lbs then maintained. Nothing else unless she starved herself. Poor lady even tried to do so but she couldn't last all day being so hungry.
Enter Mounjaro for the both of them and what do you know? Mounjaro fixed the metabolic dysfunction and insulin resistance in their bodies so that their normal diets and not-anywhere-near high calorie intake than their bodies could burn became enough; their bodies stopped storing fat like it was going out of business and started burning fat like a normal person's body. The weight started melting away 2lbs a week, 4lbs a week, 6lbs a week and it has been going down since.
Lady B has gone from obese to overweight from a bmi of 34 to 27 and will soon get to a healthy weight with MJ. Lady A has also gone from bmi 41 to 30 and will soon be out of the obese category heading to a healthy weight for the first time in her life.
So no, it can be more complicated than just what you ate. For some people, they eat the same things and even less than others but still gain weight or not lose weight (if they're already obese) due to their body not working properly. Mounjaro fixes these problems in the body and these are some of the people who will likely need to be on it for life if they want their bodies to continue to function properly and maintain their healthy weights.
If Lady B got off Mounjaro, she may still be able to lose/maintain weightloss only if she's off the meds that wrecked her system. Since she'll need to be on those for life too, then Mounjaro is just an addition to her lifelong medication. They're all fixing something dysfunctional in her body except that MJ is fixing what the other meds have broken.