food to burn fat

I am a Rheumatoid Arthritis patient and I am over weight. I am advised by my doctor to lose some weight because being heavy will mean more work for my knees and joints. I told my doctor that I am always watching the food I eat and I do walking for thirty minutes every morning but I just can't lose weight. He told me that he will give me list of food to burn fat. Maybe this will help me in losing weight.