Exposure to ambient light while sleeping at night can lead to an elevated heart rate and increased blood sugar the following day. According to a new study published in the Proceedings of the National Academy of Sciences, researchers at Northwestern analyzed the effects of sleeping with moderate light and sleeping with dim light. Participants exposed to moderate light displayed a heightened level of alertness. They also demonstrated increased insulin resistance the next morning, which can cause elevated blood sugar levels. Over time, light exposure while sleeping can lead people to becoming more overweight and obese. In addition to keep the lights off in your bedroom, if you have a TV in the room, turn it off. Bottom line: If you can see well in your room, it’s too bright.