You may be experiencing water retention Weight loss is not a linear process — it's full of peaks and valleys. Some days you may lose weight, some days you may gain weight, and some days your weight may not change at all. Part of the reason your weight fluctuates is because of fluid shifts or water retention.

Trust us, nothing works better than resistance weight training if your goal is to build a healthy muscle mass. In fact, several studies including the one published in the Journal of the American Medical Directors Association, found that skinny women quickly gained muscle when they did weight training regularly.