You exercise every day. You track your calories on a food app. You take your supplements religiously. But no matter what you do, it seems like you’re fighting an uphill battle on the treadmill and your weight won’t budge. If this is you, this story may interest you. I was training a guy who worked the early morning shift in the media industry. He would get up at 2:30 a.m. to make it to his job by 4:30 a.m. By Friday, he was so sleep deprived that he would be falling asleep at the wheel on the way home during lunchtime. He was obese, more than 100 pounds overweight. No matter what tricks I would try with him, I couldn’t get his body to lose more than five pounds. Which is pretty surprising because my methods always work. Then the station changed his schedule, and he was moved to afternoon segments. This meant that his work start time would change to 1:00 p.m. and he could “sleep like a normal person.” Want to know what happened? I didn’t change one thing. His diet was the same. His workouts were the same. The only thing he changed was his sleep schedule. He was getting seven or more hours of uninterrupted sleep per night. The change was incredible. In one month he lost 15 pounds; in two months he lost a total of 25 pounds! It sounds counterintuitive that the more you rest the easier you can lose weight, but studies have shown that the less sleep you get, the more stressed your body is. When your body is stressed, it produces a hormone called cortisol. When cortisol is released in the body, your blood sugar goes up, causing insulin to be released. When insulin is released, it signals your body to store fat. Interestingly, high cortisol levels have been associated with high amounts of visceral fat. This is the fat that surrounds your vital organs and can wreak havoc on your health. It’s basically belly fat. Studies have found that those who slept less were not only heavier, but their weight was concentrated in their stomachs. Visceral fat (more than adipose fat, or fat located in the hips) is associated with diabetes, cardiovascular disease, and other problems. Recent studies have uncovered even more interesting findings. Bruce Bailey, an exercise science professor at Brigham Young University, studied over 300 women and found that those with the healthiest sleep habits had the lowest body fat. But it wasn’t just the amount of time they slept. He found that those who slept between 6.5 and 8.5 hours (with the “sweet spot” being between 8 and 8.5 hours) per night were the trimmest, but timing and consistency also played big roles. A consistent bedtime and, more importantly, a consistent wake time were essential. Those with more than 90 minutes of variation in sleep time had higher body fat than those with less than 60 minutes. Wake time was linked to body fat as well. Those who woke up at the same time every morning had lower body fat. Bailey concluded that staying up late–and even sleeping in–can do more harm than good. The quality of sleep ranked pretty high in importance also. Those who experienced consistent, uninterrupted sleep felt better and ate better the next day. Bailey’s prescription for a good night’s sleep? Make sure the room is dark and cool and that you don’t use your bed for anything other than sleeping (well, almost anything).