Probably the latest version of the metabolic recovery type stuff Matt Stone used to talk about at 180 degree health. The whole dieting ruins your body's metabolism so you need to eat intuitively and eventually things will sort themselves out.
I'm pretty sure rats and mice eat "intuitively." Expose them to our modern foods, and they get quite plump. Inuition sucks... so does instinct. It's why we're able to trick fish into hitting lures instead of looking for a safer, yummier natural alternative. Intuition is the default. In a world full of human tricksters wanting to make a buck selling you fruitloops, the default sucks. People fail on diets because, if you stop treading water, you sink. I think my highly ketogenic diet works in part because my particular plan calls for large amounts of heavy cream, defaulting to homemade ice cream isn't that hard to do. If you can find something that appeals more than the SAD, things get easier. A Paleo/caveman narrative can be fun, maybe it helps us adhere partly for the same reason that a kid might rather have noodles or chicken nuggets shaped like little dinosaurs.
There's a grain of truth--take somebody starving themselves, refeed them, and they'll overshoot fat mass. Eating to satiety, over time they'll go back to their original, lower bodyweight, or thereabouts. People apply this to people on yo yo diets, blame the down part of the diet for the up part. Certainly there's an association. But who goes on a yo-yo diet? People who notice their weight trending up. So, are the bounces up caused by the dieting down? Or is the dieting down just obscuring things, masking what would otherwise be a more steady trend upwards?
The usual study trotted out for evidence of calorie restriction tanking the metabolism and causing this weight gain once the diet is over is the Minnesota Study. This is a horrible misuse of that study. They called it a semi-starvation study, but the only thing that kept it semi- is that it didn't go on just a little bit longer, the subjects became quite emaciated. Weight rebound, body fat overshoot from such a point is a real thing. It's characteristic of recovery from near starvation, but it's not been shown as an explanation for a guy at 20 percent body fat dieting down to 15 percent body fat and then subsequently gaining to 25 percent body fat when he goes off the diet.
You'll hear five, or maybe six percent of diets are successful.
My diet history. Before going low carb, I probably dieted at least once a year, starting in my late teens. That gives about a dozen attempts. Then low carb worked, brought me down to 170. A few false starts, do those count as dieting attempts? Call it 15 attempts until that 170 held. Even then I got to "fail" at dieting, since I tried multiple times to get down below 160 consistently. Let's be very conservative and call it another five... that's 20 diets I've been on that "failed." For the last five I get to be a successful maintainer and a failed dieter simultaneously.
Of course this is mostly poorly documented... But is my claim hard to believe? How many people go on a diet every New Years? Most of my diet attempts failed, not because dieting doesn't work, but because I didn't know how to make a diet work. If twenty people try something, and nineteen fail--I think the number is largely made up anyways, but if they do--what if those nineteen try again? Yeah, the process can take an embarrassingly long time. It did for me. Taking a year or two to entertain "diets don't work" would have just prolonged the process.