If you want to slim down for good, lose the fad diet. Don't even exercise (not for this anyway). Instead, do this: cut your portions, and cut bad foods.
We were talking over on the forum about how people in general have gotten a lot fatter. In fact it is to the point that people often do not notice it. And you are not generally allowed to talk about it in polite company.
Some years ago, we had a great article on men's weight loss here from Eric Reeves. The tips in this article are different from the tips in that one. So for good measure I suggest you read that one too; then just pick the strategy that appeals to you most.
When I went to university, I put on a lot of weight. I was reed-thin when I started school at 19. I was so skinny then one of the grizzled old roughnecks in the auto shop I worked at used to mock my walk, hounding me about "Why do you walk like that, man? Like you're some big guy?" I was just thin.
I began to lift weights hard in college to bulk up. I consumed a lot of protein powder (which I don't recommend anymore), but otherwise ate almost straight junk food. Pizza, French fries, potato chips, cookies, soda, and a couple bottles of cheap Nikolai vodka every month rounded out my diet. I was at McDonald's, Burger King, or Wendy's almost every day of the week.
I did put on a bunch of muscle, but I also added a big, sloppy gut, and got fat in the face. As this happened to me, I did not really realize it, and nobody told me. It wasn't until I started to spend time around friends and girlfriends from the third world, mostly after I graduated college, that I found out I was overweight. They told me right to my face: they told me I was fat and pointed out my big gut ("Look at that belly!"). I'd spent much more time around Americans but none of them had ever said a thing to me about it.
It still took me almost a year once I realized I was fat to actually start to lose weight. I'd tried to before I succeeded, but none of the stuff I tried before I succeeded worked.
This post will give you everything you need to slim down to healthy weight and stay that way.
It gives you the stuff that I found that works (simple stuff), and leaves out all the complicated stuff people try and fail and multi-billion dollar industries exist to serve.
Mandatory disclaimer: I am not a doctor and this is not professional medical advice. Before you do anything that affects your health you should go and talk to your doctor first. Just be sensible.