You might want to read about Sommersizing at the American Cancer Society's web site on fad diets (link below - sorry my HTML is off).
Suzanne seems to make some statements that are completely unfounded scientifically.
I've been on a weightloss program for 6 weeks and have lost 20 pounds (and according to the Tanita scale, most of it is fat not muscle). What is important is that you learn what is healthy to eat, and PORTION CONTROL. If you need a diet to learn portion control, then you need a diet. It's like being in training for an athletic event. You follow a training schedule.
The advice "just eat what you like but in moderation" and "just leave a little extra on your plate" does not work at all for me. That's too subjective. How much is moderate? My moderate may be gluttony for you. I needed a weight loss clinic to monitor me very closely and reteach me what and how much to eat. I eat twice as many vegges now and almost no starchy carbohydrates (1 serving/day).
My diet (Physician's Weight Loss Center Accelerated Plan IV) sounds horrible: 700 calories a day, 45% protein, 15% fat, 40% carbs (mostly fibrous vegetables, 1 fruit and 1 pc of bread a day) but I lose 3 pounds a week consistently. You do have to feel the pain to gain - or to lose. I had health problems related to obesity. Well, I'm not obese anymore!
You also will need a counselor or group support for maintenance when you finally up your calories to your BMR rate. This is when mot people go overboard. After you lose all the weight, your BMR will be much lower. All this is hard to do on your own. I don't like the weight loss centers that make you buy their food - you need to learn to make your own choices and cook light.