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Insufficient Sleep Affects Fat Loss

Ever feel like you’re doing everything “right”, but you still can’t manage to shed off those excess pounds? Are you adhering to a diet and a consistent training program, but you’re still not seeing results? Or maybe your fat loss or fitness progression has stalled? Then you might want to consider another variable that may be inhibiting your progress: sleep.

As a recent college graduate, I understand how easy it is to get caught up in life’s bustling adventures. Going to school full-time, working 2 jobs part-time, and exercising 6 days a week while managing to squeeze in a social life on the weekends took quite a toll on my energy levels. I was meal prepping and eating “clean” most days of the week and I was strength training 6 days a week, but I still wasn’t seeing any drastic changes in my physique. Eventually, any progressions in my strength stalled and I thought to myself, “Maybe I wasn’t trying hard enough?” Little did I know that my lack of sleep was the barrier to reaching my health goals.

I believe that we live in a society that highly values individualism, independence, and ambition, and as adults we often get swept up in the flow of it. Sometimes, we get so caught up in maximizing productivity that we sacrifice some sleep here and there to complete our daily tasks. Sometimes, we correlate how tired we feel at the end of the day with productivity, meaning the more tired you feel = the more productive you were. We normalize the idea of powering through the work week, no matter how sleep deprived and exhausted we feel. After all, we have the weekends to catch up on sleep right? But sleeping in on the weekends sometimes just isn’t enough.

The Centers for Disease Control and Prevention (CDC) recommends getting 7 to 9 hours of sleep for adults. Chronic sleep deprivation has been associated with higher body mass index (BMI) and undermines dietary efforts to reduce adiposity. Although lack of sleep alone does not make you retain or gain fat mass, it may however, increase your hunger levels, negatively affect exercise performance by decreasing cognitive function, and decrease the number of calories expended through non-exercise activity thermogenesis (NEAT—the calories we burn through physical activity that isn’t planned exercise or sports).

How Does Sleep Loss Negatively Affect Fat Loss?

Sleep Loss and Increased Food Intake

Have you ever noticed how staying up late at night tends to trigger your midnight or 9:00 pm cravings? Unsurprisingly, one function of sleep is to conserve energy. Insufficient sleep disrupts this energy conservation, thus leading to decreases in the satiety hormone leptin and increases in the hunger-stimulating hormone ghrelin. Total daily food intake, especially carbohydrates, has been shown to be greater during sleep loss beyond the necessary amount required to meet energy needs, thanks to ghrelin. To put it simply, to meet the energy demands of wakefulness during sleep loss, we tend to overcompensate by eating more. In addition, nighttime consumption of post-dinner carbohydrate, protein, and fiber calories was 42% higher during sleep loss. Interestingly, studies have also shown that post-dinner snacks induced by sleep loss tend to be more carbohydrate-rich—not that carbohydrates are bad for you, but energy-dense carbohydrates instead of nutrient-dense carbohydrates in excess can contribute to weight gain. (Markwald, et al., 2013).

Sleep Loss and Decreased Energy Expenditure

Ongoing depletion of energy stores as a result of insufficient sleep is accompanied by metabolic, neuroendocrine, and behavioral compensations to declines in resting metabolic rate (RMR) and expenditure from activities of daily living. (Nedeltcheva, et al., 2010). Think of sleep as charging your body’s battery, your energy storage. Without adequate sleep, your battery isn’t fully charged. Thus, when you go about your day with a half-charged battery, your body’s metabolic system and neuroendocrine system does whatever it can to save your energy, and it does this by decreasing your expenditure from physical activity and decreasing your RMR. An iPhone does the same thing when it reaches 20% of its battery; it goes on “Low Power Mode” and temporarily reduces background activity until you can fully charge your iPhone. What does this all mean? Your body doesn’t efficiently expend as many calories when you’re sleep-deprived compared to when you get a good night’s rest.

Sleep Loss and Decreased Cognitive Performance

Studies show that greater total sleep loss results in poorer overall mood states, with increased fatigue, confusion, and depression, and decreased vigor and liveliness. In addition, decreases in logical reasoning, coding, decision making, and filtering efficiency have been reported with insufficient sleep. Furthermore, the speed and accuracy at which these tasks are performed are negatively affected by sleep loss. (Fullagar, et al., 2014). Not only can decreased cognitive performance affect your work performance and daily tasks such as driving, but it can also negatively affect the quality of exercise. Without sleep, your concentration and energy placed into your workouts may be suffering, putting you more at risk for exercise-induced injury.

So after re-evaluating your nutrition and training, maybe it’s time to consider your sleep quantity and quality. Pay attention as you move through your days and note how you feel after doing usual activities. Are you feeling drained from your everyday tasks? Are you noticing any declines in your cognitive performance? Are you noticing any declines in your exercise performance? If you have trouble sleeping or believe you may have a sleep disorder, it is recommended that you consult with your healthcare professional or with a sleep specialist. Remember, sleep is just as important as nutrition and exercise is to a healthy and happy lifestyle!


Markwald, R. R., Melanson, E. L., Smith, M. R., Higgins, J., Perreault, L., Eckel, R. H., & Wright, K. P. (2013). Impact of insufficient sleep on total daily energy expenditure, food intake, and weight gain. Proceedings of the National Academy of Sciences, 110(14), 5695-5700.

Nedeltcheva, A. V., Kilkus, J. M., Imperial, J., Schoeller, D. A., & Penev, P. D. (2010). Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of internal medicine, 153(7), 435–441.

Fullagar, H. H., Skorski, S., Duffield, R., Hammes, D., Coutts, A. J., & Meyer, T. (2015). Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise. Sports medicine, 45(2), 161-186.

Cindy Bui holds a bachelor’s degree in Kinesiology with a specialization in fitness. She holds certifications such as Certified Group Fitness Instructor, Certified Gravity Ball Instructor, and Certified Remedial Exercise Consultant. Cindy hopes to share her passion for health and fitness by shedding awareness on evidence-based nutrition and exercise.

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