Thirst usually occurs when people are 1-2 percent dehydrated, Dr. Chorley says. It can masquerade as hunger and the body doesn’t know the difference. Avoid the confusion by drinking water before it's mealtime. You’ll also feel fuller so you won’t end up eating a lot of food. Doctors recommend that people check their sweat rate during different parts of the year. “This way you can replace fluid at a rate consistent with your sweat rate, because there is so much difference in sweat rate by weight, gender, acclimatization, and fitness,” Dr. Chorley adds.