According to a small study published in the journal Annals of Internal Medicine, people who slept for 8.5 hours a night for two weeks lost nearly twice as much weight on average than participants who slept 5.5 hours per night, despite the fact that they followed the same diet and workout plan. That's because when you get a good night's sleep, your hunger hormones, like ghrelin and leptin, stay in check. That means you're not going to wake up with a sudden hankering for a bacon, egg, and cheese. (Start working towards your goals with Women's Health's Body Clock Diet.)
Remember that it takes a 3500-calorie deficit to lose one pound of fat. That is, you have to either burn off 3500 calories through exercise or eat 3500 calories less than you burn in a week. Break this up into daily limits. To burn 3500 calories a week, you should aim to have a 500 calorie deficit every day. For example, you can exercise to burn 250 calories and cut 250 calories from your diet.
The prevailing formula for a long time on how much fat you’re going to burn was calories in minus calories out, based on your basal metabolic rate (BMR) and exercise efforts, explains strength and performance specialist Joel Seedman, Ph.D., owner of Advanced Human Performance in Atlanta. But with all the different biochemical reactions in the body, hormonal response, and endocrine function, there are an infinite number of factors that can affect how your body is storing and breaking down calories.