Stretch marks are caused by sudden weight loss or weight gain or sometimes due to lack of physical activity. I think having water/juice fast will reduce stretch marks, but to reduce stretch marks in an effective way regular exercise and massage like massage palper-rouler with any oil is a must all over the affected area. Strength training exercises firm the skin and reduce the look of stretch mark while massage rejuvenates the skin and improves dead cells and helps to build new cells eliminating stretch marks.