Can Poor Sleep Really Cause Weight Gain? Have you noticed that after a bad night's sleep you're hungrier, craving more junk food and generally can't be bothered to move as much? That's not just in your head. Poor sleep doesn't magically make you gain weight, but it can make losing weight much harder. It can affect your appetite, food choices, energy levels and how your body handles blood sugar. After 40, when losing weight can already feel harder, sleep is something that's ea