I've yo-yo'd my weight for years... decades really. Not by choice. I'm fully aware it's not a healthy way to go. Both my parents were heavy and I was heavy from 1st grade (but only really big in high school when we had some family issues and ate out every night of the week, plus late night diner/pizza runs with friends). I'm convinced that my weight issues are 50% bad choices / upbringing, and 50% biological (mental and physical). I've usually kept my peaks and valleys in a pretty set range until this last time where I blew through my peak by 15 pounds (35.5 BMI). The lowest I get is 28 BMI which isn't even close to normal. I truly think I'd be in the hospital if I hit "Normal BMI."
I find that the only way that I lose weight is by cutting out most carbs, certainly processed carbs. That's not news to anyone. My secret weapon to not having salad every damn meal is quinoa. It gives me the satisfaction of a grain like rice or pasta, and it really doesn't seem to negatively impact weight. I also have to weigh myself regularly. That's especially true for me to try to maintain my weight. I keep a spreadsheet. Out of site, out of mind, and I can put weight back on real quickly if I don't track. Of course, the more I put on, the less likely I am to check. When I kept weight off the longest (for a couple years), I would add "Key Events" to my spread sheet with a required weight. That kept me motivated. They could be big events (reunions, parties) or little things just to keep motivated. I've also done online diet bets for small amounts of money, but it's motivation.
I'm currently down 21 pounds from the recent extreme peak. This all seems crazy, but I don't like the way I feel when I get to my maximum capacity. Thankfully, while my 6th graders aren't skinny, they are a fine weight.