Leptin resistance is said to be the failure of the produced leptin hormone to burn fat in your body. This is said to be the case with obese people. Leptin is responsible for burning fat. If your leptin hormone is not functioning well, then you will most probably accumulate so much fat and not be able to burn it at all, no matter how strenuous or strict your exercise program is. When there is leptin resistance, weight loss is utterly impossible for these people.