In primary school, we were told that "You snooze, you lose." Now as adults, we know sleep is important, but when life gets hectic it's often the first thing we cut out. That's truly our loss. In fact, crappy z's could be a big reason you aren't losing weight. Here's why.
This might be confusing when you think of weight loss strictly in the context of "calories in and calories out". But remember that our bodies are complex, biological systems that take big, steaming dumps on mathematical logic. Unlike machines that only work with raw inputs and outputs, we must work with numerous confounding variables, one of which is obviously the body's capacity to repair and recover (a.k.a. sleep).
Sleep is the X factor, and when it's in short supply, the body kick-starts a cascade of complex physiological (and behavioural) effects.
Sleep Deprivation Leads to Greater Hunger and Appetite
These two hormones have big roles in controlling appetite and body fat. Leptin in particular acts according to several factors: how well-fed you are, how much fat mass you have, and your individual hormonal environment (which can vary depending on your gender).
Ghrelin on the other hand, is the hormone responsible for increasing hunger. Leptin decreases hunger. Generally, when it comes to weight loss, the more leptin, the better.
Unfortunately, leptin levels (and subsequently, leptin sensitivity) can be out of whack in obese subjects, dieters, and -- you guessed it -- those who don't sleep enough.
Researchers from the University of Chicago found that sleep deprivation adversely affected dieting efforts by decreasing leptin and increasing ghrelin levels. Essentially, this combination means you experience greater hunger and appetite, which together promote overeating. Have you ever noticed that after a terrible night of sleep, you have the snack attacks? Maybe you make more impulsive decisions to reach for doughnuts, cupcakes, and other really sugary snacks; and you're prepared to fight the jerk who asks you, "Should you really be eating that?"
In effect, it becomes harder for you to stick to a sensible diet regimen to continue with weight loss. Interestingly, one study's findings suggest it may take just one night of sleep deprivation to feel these changes.
Less Sleep Means Less Willpower
Normally, if your brain were firing on all cylinders, you'd dip into your finite resource for self-control and perhaps decide, "Not today, doughnuts." But thanks to your sleep-deprived brain, you're easier to anger, have a dulled ability to make sound decisions, and more importantly, have less willpower. Plus, dieting already seems to decrease your willpower reserves, so in combination with the increased hunger you experience from said dieting and the lack of sleep, you may require even more willpower to continue your efforts.
So, when you haven't slept enough, you are faced with the deadly combination of wanting more sugary snacks, being hungry for them, and having less self-control to make the decision you know is right. Bye bye, calorie deficit, you'll be remembered fondly when it's time to step on the scale.
Clearly, this is a vicious cycle of forces working against your weight loss efforts -- compounded by insufficient sleep. With such limited supply of willpower, you would benefit far more by using it to improve your sleep habits and quality, rather than on things like "cutting back on sodium" or "drinking so and so amount of water a day". They will have much less of a return on your willpower investment.
Lack of Sleep Makes It Harder For You to Lose Fat
Increased appetite and hunger are just part of the weight loss equation. Lack of sleep also makes it harder for your body to lose fat.
One study published in the Annals of Internal Medicine sought to observe how much (or little) sleep can influence fat loss (internet fist bump to Greg Nuckols of Strengtheory for the study). Researchers divided 10 average overweight individuals into groups that slept 5.5 and 8.5 hours a night for 14 days. The subjects were all sedentary and also had their calorie intakes very tightly controlled, consuming about 1,460 calories divided daily among breakfast, lunch, dinner, and an evening snack.
At the end of the study, both groups lost about the same amount of weight, but the difference is in what type of weight was lost. Those in the group that slept 8.5 hours lost about half of the total weight in fat mass, and the 5.5-hour group only lost a quarter of their weight from fat mass. To add insult to injury, those in the 5.5-hour group actually lost more lean mass. Yes, that means muscle.
The findings suggest that even though all of the subjects were on a weight loss protocol, the dropped weight in the 5.5-hour group came primarily from stored glycogen, or carbohydrates essentially, rather than body fat. To quote the study's authors:
Together, these results suggest that the loss of sleep at times of limited food intake amplifies the pattern of ghrelin-associated changes in human hunger, glucose and fat utilization, and energy metabolism. Thus, the increased loss of fat-free body mass during the short-sleep condition of our study may be due to increased conversion of body protein into glucose to support the more prolonged metabolic needs of the waking brain and other glucose-dependent tissues.
In other words, too little sleep while dieting puts you in the not-so-fun zone where you may need to diet for longer periods of time to get leaner, while still dealing with imminent "hanger"-induced outbursts.
How to Get Better Sleep
OK, we know that more and better sleep positively impact weight loss, but the advice to simply "get more sleep" is just as amorphous and vague as "eat less, move more."
So, let's start with how much sleep is "adequate."
The truth is that "adequate" sleep is different for everyone, and even then it varies based on age and other factors. The National Sleep Foundation recommends between 7-9 hours for adults, which seems to be the sweet spot for most people.
Just like how there's no one-size-fits-all diet or exercise program, you can't slap a single magic number onto the amount of sleep for everyone. Some people can thrive on 6 hours, while others need upwards of 10 hours a night. I myself seem to be functional at 7 hours, but if I get 8.5 hours, you can find me swimming up waterfalls and wrestling bears.
We've written a more extensive article on getting better sleep in general, but here are a few things that apply specifically to fitness:
- Cut back on caffeine and stimulatory supplements in the afternoon: Most people do late afternoon, evening, or even night-time workouts -- and that's fine. Just be mindful of the amount of caffeine or stimulants you take in order to get your workout in, and see if not taking them can positively impact your sleep. Sometimes you don't even realise how much or when you're consuming them.
- Work out earlier in the day: Some people can sleep like a carcass no matter when they work out, but if you find yourself having trouble sleeping despite regular exercise, take a look at when you're working out. You might find those night-time workouts to be more harmful than helpful, so try moving your workouts earlier -- if possible.
- Stop screen time an hour before bed (unless it's part of your bedtime ritual): Much has been written on how screen time can mess with sleep cycles. For me, anything I do with a screen revs up my brain into work mode, so I avoid it. For many others, mindless TV shows or even podcasts help prep their minds for sleep, so if that's part of your bedtime ritual -- and you get quality sleep -- then by all means keep doing what works for you!
- Time your last meal of the day to avoid going to bed hungry: One of the many dieting woes includes going to bed with an overly talkative stomach, which for many people means restless sleep with intermittent thoughts of fluffy pancakes. Since it takes typically 5-8 hours for food to pass from stomach to your small intestine, you might try eating your substantial meal 3-4 hours before bedtime. I actually have a small snack an hour before. Just in case.
- Try eating carbs before bed: Before some of you decry carbs before bed, just know that eating carbs at night alone isn't what causes fatness. More in regards to sleep, an Australian study published in The American Journal of Clinical Nutrition suggested that fast-acting carbohydrates could knock people out more quickly, especially if eaten four hours before bedtime. Note that protein and fat content with the carbohydrates may change things. I'm a big fan of microwaved sweet potatoes topped with a bit of almond butter and cinnamon myself!
- Re-examine your weight loss regimen: Sometimes really crappy sleep can be an indicator of something else going on entirely. Perhaps you are actually working out and dieting too hard -- yes, such a thing can happen. That will actually run your already stressed out body into the ground and give you trouble sleeping, among other things. If that's the case, honestly look at what you are doing. If you're working out 7 days a week on 1200 calories a day, it might be time to consult a professional about your protocol.
Think of everything -- diet, exercise, and sleep -- as part of a positive feedback loop: if you're well-rested, you're feeling like a boss, getting good, productive workouts and making better diet decisions, which in turn, can help give you quality sleep and facilitate weight loss.
So, make the most out of your hard efforts with diet and exercise by emphasising sleep, too!