People don't just get stretch marks from putting on weight. If the stretch marks are going UP your leg rather than across it, its because your growing height wise. People can also get stretch marks from LOSING weight. Stretch marks are caused simply because of rapid stretching of the skin. Your skin cannot keep up with the gain/loss in body weight and then stretches to fast to accommodate, thus causing these marks. There are lots of fancy (expensive) creams out there claiming to get rid of stretch marks. Once you have stretch marks, you can't get rid of them, you have to wait for them to fade. If you want to help prevent them a cheap moisturizer will do exactly the same job as the more expensive oils on the market, drinking water will also help. Your skin just needs a bit of extra moisture, so that when it does stretch, its does so more easily, without causing these stretch marks. hope this helps :)