Lifestyle change is most effective
As others have said, stay way from processed foods, refined sugars and simple carbs (breads, pastry etc...).
I attended a convention last fall in Las Vegas of the American Bariatric Physicians, these are the physicians who deal with patients who are overweight many of them morbidly obese. At the convention I met Dr Barry Sears who developed The Zone Diet. He's very well respected and is one of the leading doctors who research issues with overweight people...Google him and you will see.
ALL of his research leads him to believe, and it was a strong theme of the convention and the expo, that you must start with reducing inflammation in order to start to have any positive effect on losing weight.
His research suggests a diet that is high in polyphenol based antioxidants is where the Bariatric world is heading. Polyphenols are the "Mercedes Benz" of antioxidants and work the best for reducing inflammation.
The reason I was at that convention was due to having participated in a 50 person medically supervised 90 day study and lifestyle intervention using a polyphenol based high antioxidant meal replacement. We substituted it for 2 meals, logged all of our food, had a 3rd sensible with protein (fish, chicken, beef, turkey etc..) and complex carbs (vegetable), exercised, got at least 8 hours of sleep and had a buddy system for accountability.
All 50 people that started the study finished it, which in and of itself was amazing as most weight loss studies lose half the participants after 2 weeks. Our average weightloss was 30 lbs after 90 days and I lost 51 lbs and 8.5 inches around my belly. Our study was peer reviewed and then featured in and (and we are on the cover or) The Bariatrician which is the journal of the American Journal of Bariatric Medicine.
1.5 years later I've still kept it off and as a group, the average is now up to 44 lbs.
Good luck! Record or write down EVERYTHING you put in your mouth, you will be surprised who often and how bad what you put in there, was by choice and that to was an unhealthy choice.