Why are people fat… gosh there are a lot of reasons.
I have a sister who actually did have a “gland” problem in high school and started packing on the pounds rather abruptly. However - and I really think this needs to be emphasized - there were other symptoms beside just weight gain. She went from 50 mile back-to-back bike rides on the weekends and lots of school and extracurricular activities to sleeping 16 hours a day, hair falling out, oily skin to skin so dry it cracked open into bloody gashes, and so forth. IF you have a medical condition that causes weight gain you’re going to have other symptoms besides weight gain. elliot with PCOS no doubt had other symptoms than weight gain as well.
Some medications can cause weight gain - someone with severe asthma, for instance, may be on oral steroids and gain weight even on a very low calorie diet. Again, they’ll show other symptoms as well - thinning skin, for instance, as well as breathing problems that may interfere with activity.
So yes, there are a number of people where a medical condition contributes to weight gain and/or obesity. These unfortunate people will have to work much, much harder than average to maintain their weight, much less lose it.
However, someone overweight who is full of boundless energy and is not exhibiting other medical symptoms is most likely simply eating more calories than he/she is burning. For a variety of reasons.
Myself - I’m 5’3" and 150 lbs (that’s a BMI of 26, I think), girl-measurements of 34-28-38. I’ve stayed between 145 and 150 lbs for the last 20+ years. I feel that a stable weight is far preferable to yo-yo’ing up and down. For better or worse, I don’t have a picture of me available to show ya’ll, but most people do not perceive me as overweight when they meet me in person, and quite a few of my fellow women (who we know are often harsh critics of their peers) have described me as “thin” or “slender”. At this point, I need to exercise a little more to improve my muscle tone (this getting older thing can be a drag at times, and the body is requiring a little more maintenance than it used to) but frankly, I’ve decided that as long as I’m 150 or under I’m just not going to worry about the matter. I feel healthy. I can climb 4 or 5 flights of stairs at a go without getting out of breath. Walk 5 miles without getting sore. Bike 10 the same. Items like cholesterol, blood sugar, blood pressure, etc. are all normal or better than average. I will never look like a Calista Flockhart, and I’m not going to make myself miserable trying.
It’s more than just fitting in a certain size of clothing, or a wrist measurement. You have to look at the total person. How are their heart, lungs, blood sugar, cholesterol, joints, blood pressure, etc? Are they battling a medical condition that makes it more difficult for them to exercise? I really hate one-size-fits all recommendations. People vary considerably, and what works to maximize health in one person may be unhealthy for another.