Sustainability

That's how you know that your diet will work.  There are so many diets there, and I am sure that most of them work.  Right now, you can take your pick of healthy and/or unhealthy diets.  You can do low carb, no grain, all grain, vegan, all meat, raw food, you name it.  Someone out there has a plan for YOU!   LOSE WEIGHT FAST! That is their claim, and they are sticking to their story.

The question is not if you can lose weight, but if you can keep it up long enough to lose the weight you need and not gain it back.  For that you need a sustainable plan.  Probably you need a plan you can live with for the rest of your life.  This is where fad diets and radical exercise programs are not going to be your friend.

Any plan for anything that promises instant results for little-to-no effort is probably phony.  Anything worthwhile in this life requires long-term changes and a real effort.