Metformin works to decrease insulin resistance and help the body to be able to move those pesky little molecules into the cells where they belong. There are a few different reasons why insulin causes weight gain. Probably, the most significant reason is that insulin reduces the removal of glucose through the urine. With uncontrolled diabetes, the body cannot use (or store) glucose properly, and glucose is lost through the urine. This means that you can consume more calories than you need, and your body cannot use it or store it as fat as well as normal. As soon as you correct the situation with insulin, all of a sudden, your body can access the glucose in the blood. Any excess glucose is not lost through the urine; it is stored as fat.Is it metformin that helps with insulin resistance? I know there are insulin-dependent diabetics who DO take metformin . . . could that be why? And metformin, for me at least, curbs my appetite too.