Have you gained weight or are you just retaining water? The human body is made up mainly of water; around 60% total volume. When your hydration level is not balanced, and you are not drinking enough water, your body will hang on to it or “store it”. So, when you stand on the scale, your body’s weight goes up because water is heavy. We call this water retention. It can cause you to feel less nimble, or less active. It can also cause: bloating puffiness Swelling Water retent