Sleep

5 ways sleep affects your weight

More sleep may not help you lose weight overnight, but research shows that good-quality sleep can support weight management in other ways. Here’s the science on sleeping and the scale.

Fluff the bed pillows and get ready for yet another reason to love a good night’s sleep. Those hours you spend in dreamland could make a positive difference in your weight-loss journey.

Growing scientific evidence suggests that sound sleep may support healthy weight management—in the short and long term. “Sleep ranks right up there with healthy eating and exercise when it comes to [attaining] healthy weight goals,” says sleep expert, Marie-Pierre St-Onge, PhD.

Does this mean you can lose weight simply by sleeping more? Not quite—experts aren’t suggesting that sleep automatically makes weight disappear. But the amount and quality of shut-eye we get each night could potentially affect everything from our next-day snack choices to our mental capacity for following a meal plan.


1. Sleep influences appetite


If you feel ravenous after staying up too late, know that it’s not your imagination. “Reduced sleep dysregulates appetite hormones,” says Abhinav Singh, MD, a medical review panelist for SleepFoundation.org. Sleep deprivation is associated with increased levels of ghrelin, a hormone that helps signal hunger, as well as reduced levels of the hormone leptin, which is linked to feelings of satiety (fulless), Dr. Singh says. While there’s no “perfect” amount of sleep that suits everyone, a 2018 research review found that this hunger-inducing hormonal effect tends to kick in when sleep duration dips below seven hours.


2. Sleep may affect cravings


In addition to dialing up appetite in general, lack of quality sleep may influence our food choices—and not in a way that makes us crave a plate of fresh veggies. “Sleep loss increases activity in brain areas associated with reward,” Dr. St-Onge explains. “These signals seem to increase motivation to seek foods that are high in [unhealthy] fat and calories.” Quality of sleep matters, too, she adds. In a small 2020 study of women published in the Journal of the American Heart Association, volunteers who reported sleeping poorly tended to consume more added sugars and fewer foods containing healthy unsaturated fats than those who snoozed more soundly.


3. Sleep can support workouts


It’s no secret that getting into an exercise groove can help people manage weight. The challenge is that being active takes mental and physical oomph—and being well rested is key to both. In a 2019 survey of 1,011 adults by the US National Sleep Foundation, nearly half reported that sleepiness hampered their ability to exercise. Fortunately, there’s more to the story than that—previous research suggests a link between sleep and activity levels. This means that sleep may encourage you to become more active and becoming more active may support better sleep. If you’re feeling unmotivated to hit the gym, focusing on your sleep habits first may help workouts feel more doable.


4. Sleep can help you stick to a plan


There’s a reason you might feel like your whole world is in disarray after a few nights of tossing and turning. Poor sleep can hamper executive functioning, the set of cognitive processes that help us organise our time and tasks, solve problems and manage impulses, notes a 2017 report in the journal Nature and Science of Sleep. This can make a weight-loss plan (pretty much any plan, to be honest) challenging to follow, Dr. Singh says. For example, a groggy brain may not have the bandwidth for healthy meal planning—leading you to grab a less than ideal lunch on the go—or for prioritising the yoga session you had hoped to fit into your busy day.


5. Sleep is linked to metabolism


The stage of sleep characterised by dreams and rapid eye movement (REM) may be a factor in how many calories the body burns at rest. During REM sleep, heart rate increases and brain activity most closely resembles that of a wakeful state. All that action requires glucose as fuel, which leads to a higher resting metabolic rate—the energy a body needs for basic functioning, Dr. St-Onge says. People cycle through REM and non-REM stages repeatedly during sleep, with REM periods getting gradually longer as the night goes on. That means if your sleep is cut short, you lose out on those extended REM stretches. A small study published in the journal Obesity found that volunteers who were woken after a mere four hours of sleep woke up with 2.6% lower resting metabolic rates compared with their baselines. Dr. St-Onge says, “This could make weight-loss or maintenance harder.” More research is needed to determine actual effects on the scale.

Another metabolic note, compared with people who get adequate sleep, is those who consistently get short sleep are more likely to exhibit decreased insulin sensitivity and increased concentrations of a stress hormone called cortisol. This dual hormonal effect could raise a person’s risk of developing pre-diabetes or type 2 diabetes.


The upshot: Can sleeping more help you lose weight?


Right now, there’s not enough evidence to state that sleeping itself can speed up weight-loss. Growing scientific evidence does show, however, that falling short on sleep can affect your mood and mindset, as well as the hormones your body secretes and the foods you desire—all of which could lead to gaining weight. Struggling to get enough shut-eye? Experts tell WW that taking steps such as establishing a consistent bedtime routine, being active during the day and staying off digital devices at night may help you sleep better and longer. Chat with your doctor if tossing and turning persists. You deserve good-quality rest.