I would have agreed with you completely before this summer. I had done weight watchers and lost weight, but as soon as I stopped tracking my diet (and restricting my calories), my weight drifted right back to where I started. Gary Taubes has a whole section in Why We Get Fat on how you can't keep weight off by temporarily restricting calories.

This summer I've been reading a lot of books [1] on a low carb, moderate protein, high fat diet. It is called a LCHF or Keto diet. I now think that insulin resistance has a lot more to do with weight than I realized. I've lost 30 pounds this summer without counting calories (or weight watchers points). I just keep my carbs below 20g a day, and try not to eat too much protein. I'm not hungry, it doesn't take time to track, I feel really good, and the weight has some off so much faster than with weight watchers.

[1] My summer reading, that has really changed my life:

Why We Get Fat, by Gary Taubes

http://www.amazon.com/Why-We-Get-Fat-About/dp/0307474259

The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet, by Nina Teicholz

http://www.amazon.com/Big-Fat-Surprise-Butter-Healthy/dp/145...

Death by Food Pyramid: How Shoddy Science, Sketchy Politics and Shady Special Interests Have Ruined Our Health, by Denise Minger

http://www.amazon.com/Death-Food-Pyramid-Politics-Interests/...

Keto Clarity: Your Definitive Guide to the Benefits of a Low-Carb, High-Fat Diet, by Jimmy Moore, Eric Westman MD

http://www.amazon.com/Keto-Clarity-Definitive-Benefits-Low-C...

I was really surprised that most of what the medical establishment says about diet is so incredibly backwards.