Water does not cause weight gain in healthy people. Photo Credit Digital Vision./Photodisc/Getty Images. Drinking water should not make you gain weight, since it's calorie-free. However, certain health conditions can cause people to retain water, such as kidney disease, and drinking water may cause weight gain.If you think drinking water is causing you to gain weight, talk to your doctor.ater does not cause weight gain in healthy people. Photo Credit Digital Vision./Photodisc/Getty Images. Drinking water should not make you gain weight, since it's calorie-free. However, certain health conditions can cause people to retain water, such as kidney disease, and drinking water may cause weight gain.