To answer the OP, and this is all my own personal experience. YMMV:
Weight gain is such a creeping thing. After a point, you see that you’re overweight and you realize you need to start losing weight–probably starting tomorrow.
It’s always “tomorrow.”
In the meantime, at each meal or snack, you have the attitude, “Well, I’m already fat. One more bad meal isn’t going to have much effect.”
And it doesn’t. But you have to eat again. And again. And again. You have the same attitude. And, of course, you’ll always start doing something “tomorrow.”
Also, weight loss is slow. You want something that shows results right away. But it takes time, and that is very discouraging.
I started losing weight (don’t know how much, but I pulled in a total of six belt holes), almost by accident, 6 years ago. Now, no one would ever say I am skinny, or even thin, but I am at a weight where all my clothes fit, and I’m not self-conscious. It happened over the course of a year, and have been able to keep it off, now for *five years. But that entailed doing some permanent lifestyle adjustments, not going on the latest fad diet (whatever that might be).
*Not to say that I never gain weight. Not at all. But it’s only small amounts, and I keep it in check. When I notice it, I start evaluating what I’m doing wrong, and take corrective actions.