what does sleep have to do with weight loss
Losing body fat is an arduous task. Between hours in the gym lifting weights and doing cardio, arduous meal preparation, work, school, life or whatever else you have going on in your life, it rarely feels like you get a second to lay down and just rest. But even when you are juggling all of these responsibilities, sometimes the number on the scale isn’t going down. Do you just need to diet harder? Maybe another mile on the treadmill every day would help? It’s possible. But research has shown an association between poor sleep quality/quantity and obesity that could be a contributing factor.
It seems weird, right? It’s not like sleeping burns more calories, so what’s the connection? In simple terms, not sleeping enough throws off the normal signaling pathways that occur in your body to regulate your metabolism. Normally, your hunger signals are regulated through the hunger-stimulating hormone Ghrelin, the hunger-suppressing hormone Leptin, and the stress hormone Cortisol. These hormones fluctuate throughout the day in response to a number of factors, such as meal timing but also sleep.
Studies have shown that, in the setting of sleep deprivation, Ghrelin, and Cortisol levels increase while Leptin levels decrease, leading to increased hunger signals and increased stress. While weight loss is still controlled by calories in vs. calories out, this alteration in hormone signaling makes you hungrier (disproportionately for carbohydrates, too!) and makes it harder to stay in a caloric deficit. In addition to this, the increases in the stress hormone cortisol leads to increased fat storage. This means that any weight you actually lose is more likely to be other tissue, such as muscle, rather than fat.
On top of just eating more, a study was conducted that looked at brain activity in response to food intake, which demonstrated that your brain actually responds differently to food after sleep deprivation. After as little as one night of sleep deprivation causes upregulation of your brain’s reward signals in response to food, meaning that sleep deprivation can actually make you binge, crave, and eat more because your brain is literally telling you that eating is awesome.
This association between sleep deprivation and altered hormone signaling pathways leads to more than just weight gain. Because the food that people generally eat in sleep-deprived states is carb-heavy, this can be a contributing factor to diseases like Type 2 Diabetes. Sleep deprivation has also been associated with increased waist circumference, higher triglycerides, and higher cholesterol.
Let’s look at a couple studies of real-life people.
There are 2 groups of participants who were subjected to either 5.5 hours or 8.5 hours of sleep per night for 14 days. Throughout this 14 day period, each of these participants was on a caloric deficit of about 680 calories per day. While both groups lost the same amount of weight (3kg), the 5.5 hour group, on average, lost 55% less body fat and 60% more fat-free body mass.
Another study where participants were subjected to either 5.5 hours or 7.5 hours of sleep a night for 14 days while being maintained on a similar caloric deficit. Both groups lost similar amounts of weight, but only 26% of the weight lost by the 5.5 hour group was fat, while 57% of the weight loss by the 7.5 hour group was fat.
A study involving 1224 twins was conducted where each twin was stratified by sleeping <7 hours or 7-9 hours per night. After controlling (as best as they could) for genetics and similar environments, there was a statistically significant difference between each twin’s BMI (25.7 in the <7 hour group vs. 24.7 in the 7-9 hour group).
Basically, in non-research terms, these studies suggest that not sleeping “enough” leads to a higher BMI and, in the setting of a caloric deficit, more fat retention when compared to someone who gets adequate amounts of sleep.
So what is enough sleep? The above studies seem to suggest that a number between 7-8.5 would be sufficient. How do you get there though? Try the following suggestions.
Avoid using electronics for about half an hour before bed.
Avoid eating significant amounts of sugar in the few hours leading up to bed.
Avoid afternoon caffeine, such as coffee, caffeine-containing sodas, or energy drinks.
Avoid alcohol or smoking around bedtime.
Create a calming environment in your bedroom: avoid stressors in the period leading up to bedtime, try and keep your bedroom dark and quiet (turn off the TV!)
Try to avoid long (>30 minutes) daytime naps!
Few things feel as good as an amazing night’s sleep, and it could be an incredible way to supplement you on your journey to fitness, health and #treatingyoself!
John Li is a former Division I track and field athlete who specialized in the pole vault and a current medical student hoping to pursue a career in Emergency Medicine. He can be contacted through his Instagram at @Jawn71.