sleeping man

Have you been trying to lose that last little bit of fat that just doesn’t seem to go away? Your workout program and nutrition habits may be on point, but your fat loss journey may be at a standstill because you are missing one key element: sleep. Trainers, coaches, athletes, and exercise scientists will all say that fitness is 24/7, meaning that even while asleep, progress can be made. Sleep is often overlooked as a beneficial component of fat loss and people will often think, “How bad could losing one hour of sleep really be?”

One major problem associated with sleep deprivation is increased cortisol levels during the day. Cortisol is a hormone produced by the adrenal glands that can work to break down body tissues (including muscle) when found in high quantities. Cortisol levels are also naturally increased during times of stress. When dieting, the body is put under stress by the decrease in calories, which will cause cortisol levels to rise. People who are trying to lose weight already have to deal with the risk of losing muscle mass due to the decrease in the number of calories they are consuming, so what happens to those trying to lose weight who also happen to be sleep deprived? It’s simple. They are at an even greater risk of losing muscle mass while dieting.

A lack of sleep can also lead to increased appetite. It’s no secret that when we don’t get enough sleep, we’re probably going to be tired throughout the next day (and possibly the next day). When the body is tired, it assumes that it’s because of a lack of energy, so we become hungry. What do we do when we’re hungry? We eat. Researchers have also shown that a lack of sleep can have negative effects on glucose and insulin sensitivity, which control the satiety we feel after eating.

Researchers from John Carroll University conducted a study involving the impacts of various times of light exposure on animals. Several observations were made, including levels of visceral fat levels in the animals. Visceral fat is what surrounds the internal organs and also poses the greatest health risks. It was found that animals with increased light exposure had significantly greater amounts of visceral fat than those with increased exposure to darkness and those exposed to equal amounts of light and darkness. So what does this mean for humans? It means that our bodies want to maintain its circadian rhythm and when it can’t, there can be negative results such as increased fat levels and a decline in overall health.

It is recommended that most adults get 7-8 hours of sleep each night. Some people may find that they can function normally on less sleep (6 hours or less), while others may need 9 or more hours. It is also important to take exercise into consideration. With more intense and frequent workouts, more sleep may be required for recovery purposes. If you don’t recover properly, your workouts will suffer, which will cause further setbacks. That’s why it’s important to keep well rested and get an appropriate amount of sleep. You will be less tired throughout the day, battle those cravings at night, and ultimately be better equipped to meet your fat loss goals.


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Murphy, HM., & Wideman, CH. (2009). Constant light induced alterations in melatonin levels, food intake, feed efficiency, visceral adiposity, and circadian rhythms in rats. Oct;12(5):233-40.

Leproult, R., & Van Cauter, E. (2010). Role of Sleep and Sleep Loss In Hormonal Release and Metabolism. Endocrine Development. 17:11-21.

Backx, FJ. Et al. (2009). Evaluation and opportunities in overtraining approaches. Research Quarterly for Exercise and Sport. Dec;80(4):756-64.