Losing as little as 2% of your body’s water content can significantly impair your physical performance. Mild dehydration (fluid loss of 1–3%) can impair energy levels, impair mood, and lead to major reductions in memory and brain performance. Mild dehydration (fluid loss of 1–3%) can impair energy levels, impair mood, and lead to major reductions in memory and brain performance. Drinking plenty of water may help prevent and relieve constipation, especially in people who generally don’t drink enough water. Increased water intake appears to decrease the risk of kidney stone formation. Also dinking plenty of water can help you lose weight. When do you drink water?