I got fat, then thin (starvation diets) then fat for decades until I was finally diagnosed with Hashimoto's (immune system disorder that causes the immune system to attack the thyroid hormone). Even after I was on thyroid meds for years, nobody could figure out why I was still unable to control my weight and still suffered from various aches and pains I couldn't find the source of. But I didn't give up.
I finally found a female doctor who worked with me for a year and we slowly tested everything--not just my thyroid hormone levels, but also cortisol, cholesterol, vitamin D and so on. The tests were not standard but they uncovered the fact that my body, even with thyroid tests showing no issues, did not appear to be pulling nutrients from food--I needed a variety of supplements and HRT (Hormone replacement therapy) to get my metabolism normalized.
Since then I've eaten a healthy diet and do regular aerobics and resistance training. I drink alcohol moderately and I take a lot of supplements but I feel now like I did at 38 and I'm 62.
It's a long road and takes a great deal of effort, but I hope more doctors start to realize that being overweight isn't always just about eating too much. And when a woman tells a male doctor she still has issues and needs help, instead of telling her she is wrong or has "fibromyalgia" they should try a few blood tests.