People become obese through an unhealthy diet, and THEN stopping moving around.
I was an active kid playing soccer & basketball in grade school and I biked a lot. My family lived in Oakfield, WI which is a few miles from Fond du Lac, WI, and one of my favorite things to do was ride my bike into Fond du Lac and play video arcade games at this hotel on the outskirts of the city.
Another thing that I was starting to do is buy donuts from this grocery store alone and eat them behind a business down an alley way a few businesses down Main Street. I was starting to get a little chunky then.
One day, my family moved to Madison, WI and when I was in high school, my parents gave me $5/day to buy lunch. Because I am autistic, I wanted to eat alone so I never went to the high school cafeteria to eat. I, instead, walked a few blocks to a gas station where I would get like 6 snack cakes and a soda. That was my lunch. Even though I was on the wrestling team freshman year of high school and punishing myself every night in practices, I was gaining weight which almost put me in the heavyweight weight class of high school wrestling which I believe is 200+ lbs. Sophomore year, exercise became a chore and I quit sports forever.
Before exercise became a chore, if you are familiar with Madison, I used to ride my bike in summer often on Portage road out towards Sun Prairie, then in the American Parkway area and see movies at the now closed down Eastgate Cinema near all those car dealerships. I miss riding a bike because I am so obese, I cannot pedal anymore because my belly gets in the way of my thighs.
In Madison, there was this arcade on State Street that I frequented in high school (because I had a habit of truancy) and noticed that the Pizza Hut on State Street had a $3.99 Lunch Buffet. This is how dumb my autism gets sometimes. In Madison, WIBA carried the Rush Limbaugh show from 11:00 AM to 2:00 PM CST. Guess what else was 11:00 AM to 2:00 PM? The Pizza Hut Lunch Buffet. So, I was eating pizza & drinking soda (which a bottomless soda was included in the $3.99 price back then) for 3 hours a day and that continued for years after high school and now I am 450 lbs.
Here is a study that shows that people get fat first, then stop exercising. https://pubmed.ncbi.nlm.nih.gov/20573741/
My obesity robbed me of enjoying exercise (among other things such as having a wife because no one will date an obese guy) and being physically active and one of the reasons why I want to lose weight is to enjoy being physically active again. I once saw this t-shirt on Ranger Up's website and bought one which said "Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, leaking oil, on fire and reeking of gunpowder, women, and whiskey loudly proclaiming 'Wow! What a ride!"" That is right on, in my opinion. God gave us life life to enjoy.
I started gaining weight after smoking related medical issues made it where I wasn't able to bike ride and then when I quit smoking the gains continued. I used to ride about 6 miles a day and still do a LOT of walking but when I give up smoking I replaced it with food. I've gone from 180 to 220 in 5 years but seem to have plateaued. I'm in my 60's so it may have something to do with that and family genetics. Don't know, doc ain't said nothing so I'm not worried .... yet.