You can exercise regularly and maintain a healthy diet, but lack of sleep can negate both of those practices. A recent study has found that too little sleep can change the balance of bacteria in your gut. Women who slept less than five hours a night were 15% more likely to become obese compared to women who received seven hours. A similar study found that people who slept five and a half hours or less per night consumed roughly 385 more calories a day than those who slept for seven hours. Too little sleep can affect hormones in the body that regulate hunger and hinder your desire to be active, thus causing you to gain weight.