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Why Can’t I Lose Weight? It’s More Than Diet and Exercise

Diet and exercise on point, but still can’t lose weight? You may be overlooking two things sabotaging your weight loss: sleep debt and circadian misalignment.
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Jeff Kahn, M.S., Rise Science Co-Founder
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Woman carrying scales looking upset because she can't lose weight

What are the first things you think of doing when you want to lose weight? Healthy eating and an exercise routine. But there’s actually a third even more fundamental thing to weight loss — not to mention overall well-being. And that thing is sleep. 

Getting enough sleep isn’t just good for your mood and productivity, it can also help you shift the pounds and keep weight off if you’ve already lost it. Plus, lining this sleep up with your circadian rhythm (more on that soon) makes losing weight easier.

Below, we’ll cover why if you’re trying to lose weight, there’s more to do than just calorie counting. You need to pay attention to your sleep. We explain how exactly sleep deprivation and circadian misalignment can contribute to weight gain, and how lowering your sleep debt, aligning with your circadian rhythm, and maintaining good sleep hygiene can help you lose weight. 

Why Can’t I Lose Weight When I Exercise and Eat Right?

It’s not always as simple as calories in and calories out. Science is finding out just how much sleep can impact your weight. Here’s why you may be struggling to lose weight, even if you’re in a calorie deficit.  

You’ve Got High Sleep Debt

Sleep debt is the measure of how much sleep you owe your body over the last 14 nights. So, if your sleep need — the genetically determined amount of sleep you need — is 8 hours 30 minutes, but you’ve been getting less than seven hours of sleep a night, you’ll have built up a lot of sleep debt. This, of course, affects how you feel each day, but it also works against your weight loss efforts. 

Sleeping for short durations of time each night has been shown to increase your risk of obesity

And if you don’t get enough sleep, your glucose metabolism takes a huge hit. One study found after five nights of only four hours of sleep, participants’ glucose clearance was 40% lower and insulin response to glucose was 30% lower while sleep deprived, compared to when participants were in bed for 12 hour recovery sleeps. Excess glucose in the blood can be stored as body fat, sabotaging any attempts at fat loss. 

Another study compared short sleepers, described as those who slept less than 6.5 hours a night, and normal sleepers, described as those who slept 7.5 to 8.5 hours a night. Glucose tolerance was similar for both groups, but short sleepers produced about 50% more insulin, causing a 40% lower insulin sensitivity. 

Participants who reported being short sleepers for at least six months had glucose clearance rates similar to long sleepers, but their bodies had to make more insulin to achieve this. And increased insulin levels can lead to insulin resistance, which can not only lead to type 2 diabetes, it can also cause excess glucose to be stored as body fat.

But it’s not all bad news! Sleep deprivation can wreak havoc with glucose metabolism, but meeting your sleep need can reverse the damage. In fact, one study found just two nights of getting enough sleep restored normal glucose metabolism. 

Weight loss tip: Keep your sleep debt low by meeting your sleep need each night. The RISE app calculates this for you (more on how soon). 

You’re Not Aligned With Your Circadian Rhythm 

Your circadian rhythm is your internal body clock that runs over a roughly 24-hour cycle. If you’re not in sync with it — maybe you’re a night shift worker or even just stay up later than your body wants to — this can hamper your weight loss efforts. 

In one study, participants ate and slept about 12 hours out of phase from their usual times. This was found to decrease their leptin (the hormone responsible for suppressing appetite) by 17%, increase glucose by 6%, and insulin by 22%. It also reduced their sleep efficiency — the measure of how long you spend in bed actually sleeping — by 20%, which can lead to not getting enough sleep, making weight loss even harder.

However, even when sleep efficiency wasn’t taken into account, leptin was still affected by sleeping and eating out of sync with circadian rhythm. So, even if you’re getting enough sleep, if it’s at the wrong times for your body, your leptin — and your therefore appetite — can still be impacted.

People who have a mismatch between their circadian rhythm and their schedules have been found to have a higher risk of obesity, diabetes, and metabolic diseases. Mitchell A. Lazar, MD, PhD, the director of Penn Medicine’s Institute for Diabetes, Obesity, and Metabolism believes this is caused by the metabolic stress the body experiences when you eat and sleep at times it isn’t expecting.  

A study on mice found they gained more weight, had higher blood sugar, and fattier livers if they weren’t in sync with their circadian rhythms. Mice who were in sync, even if they ate the same diet, didn’t have the same negative health outcomes. The most promising part? Once the mice got back in sync with their body clocks, they weren’t as susceptible to those unhealthy outcomes. 

Weight loss tip: Try to eat and sleep when your body naturally wants to and at similar times. The RISE app predicts your circadian rhythm each day, so you can align your schedule with it as best you can.

You’ve Got Social Jetlag 

It’s not just night shift workers who are at risk by being out of sync with their circadian rhythms. Social jetlag is when your biological clock is at odds with your social clock, like when you wake up and sleep an hour or two later at the weekend. In fact, about 87% of adults have social jetlag and go to bed at least two hours later than usual on weekends. 

But even more than one hour of social jetlag can increase the likelihood of metabolic syndrome — which includes obesity, diabetes, and high blood pressure.   

One study found people with one to two hours of social jetlag had 1.29 times the prevalence of metabolic syndrome than those who had under an hour of social jetlag. Those who had two hours or more social jetlag were even more likely to have metabolic syndrome, as they had a prevalence rate of 2.13. 

Research from 2013 found social jetlag is associated with higher body mass index, and suggested syncing circadian and social clocks can help manage obesity. 

Another study, this time from 2015, found social jetlag was associated with being overweight and having metabolic dysfunction, even after taking into account how long participants slept for. Participants with more social jetlag had higher BMIs, more fat mass, and were more likely to be obese.

Weight loss tip: Keep a consistent sleep schedule, even on weekends. Or if you need to lay in, try to keep it to under an hour. 

Why Does Sleep Affect Weight Loss So Much?

Not getting enough sleep can not only make it harder to achieve your weight loss goal, it can actually cause you to gain weight. 

You Eat More Calories When You’re Sleep Deprived  

When you’re sleep deprived, ghrelin, the hormone that makes you feel hungry, rises, while leptin, the hormone that suppresses appetite, falls. This is the perfect storm for increased hunger levels, and therefore overeating and increased calorie intake. And, most of the time, those extra calories don’t come from healthy food, we crave high-calorie foods and processed foods.

What’s more, when you haven’t had enough sleep, endocannabinoids flood your body. These are chemical messengers that signal to the brain’s pleasure receptors, making eating feel more enjoyable, and therefore increasing food cravings. This leads to — you guessed it — increased hunger and increased calorie intake. 

There’s also the simple argument that if you’re sleep deprived, you’re obviously awake for longer, giving you more time in the day to eat. Plus, not getting enough sleep can impact the brain’s prefrontal cortex and your impulse control takes a hit, making it much harder to resist unhealthy food choices like junk food. 

One study found after six nights of getting just four hours of sleep, leptin levels were about 19% lower than when not sleep deprived. The circadian rhythm of leptin was also affected by sleep deprivation. Leptin levels rose two hours earlier and were 26% lower overall, and daytime peak levels were 20% lower. And all of these changes were seen without any change in calories consumed or exercise. 

A 2016 study found after a night of partial sleep deprivation, the number of calories participants ate increased by about 385 the next day, and no additional calories were burned. So, even if we’re usually great at following a meal plan, being sleep deprived means you need to work extra hard to stick to veggies, nutrient-rich whole foods, and healthy portion sizes. You’re working against your biology, which is now craving a high calorie diet.

That’s how sleep can affect your eating habits. We’ve also covered how your eating habits can affect your sleep here. 

You Burn Fewer Calories When You’re Sleep Deprived  

But it’s not just about food. When you’re sleep deprived, you’ll feel low on energy during the day and lack motivation for activity and/or exercise. This lack of activity means your body isn’t tired enough come bedtime, making you stay up later, increasing sleep deprivation even more. All that inactivity and sleep loss leads to even more weight gain. 

After a night of sleep deprivation, the number of calories we burn goes down and the amount our body wants to eat goes up — a dangerous combination if you’re trying to lose or even just maintain a healthy weight.  

One study found resting metabolic rate — the rate your body burns energy while resting and a key part of how many calories you burn each day — was significantly lower in the mornings after getting four hours of sleep for five nights. This did recover after a 12 hour recovery sleep on the sixth night, although other similar studies have shown recovery takes nine nights of 10-hour sleeps after three weeks of sleep deprivation. 

What’s more, the amount of calories you burn goes down when you’re sleep deprived simply because you’re less likely to do a lot of physical activity if you’re feeling tired. 

How Can Sleep Help Me Lose Weight?

Convinced you need to use sleep as one of your weight loss strategies? Here’s what you can do. 

Keep Your Sleep Debt Low  

RISE app photo showing how much sleep debt you have.
The RISE app can tell you how much sleep debt you have.

Aim to meet your sleep need each night to reduce how much sleep deprivation can impact your weight loss. 

Not sure what your sleep need is? The RISE app can help. The app uses your phone use behavior from the previous year to determine how much sleep you’re getting and how much you need. This gives you a number — in hours and minutes — to aim for each night. 

The app also calculates how much sleep debt you have. We recommend keeping this number below five hours to help you feel and function at your best, as well as to reduce the chance of sleep deprivation impacting your weight. 

Need to catch up on sleep and pay down sleep debt? You can: 

  • Take naps in your afternoon dip in energy — RISE can tell you when this is each day 
  • Go to sleep a little earlier
  • Wake up a little later
  • Maintain good sleep hygiene to help you fall asleep faster and stay asleep all night — therefore getting more sleep overall 

Want proof sleeping longer can help with weight loss? A study published in 2022 looked at overweight participants who usually slept for less than 6.5 hours a night. With a sleep hygiene counseling session, they extended their sleep time by about 1.2 hours a night. This led to them eating 270 fewer calories each day. The researchers said this would equal about 26 pounds of weight loss over three years — all from sleeping a little longer.   

“We understood that sleep is important for appetite regulation,” said Esra Tasali, MD, Director of the UChicago Sleep Center at the University of Chicago Medicine. “Now we’ve shown that in real life, without making any other lifestyle changes, you can extend your sleep and eat fewer calories. This could really help people trying to lose weight.”

Sync Up with Your Circadian Rhythm

RISE app screenshot showing you when to get and avoid bright light.
The RISE app can remind you when to get and avoid bright light. 

Stay in sync with your circadian rhythm by keeping sleep, exercise, and meal times at roughly the same times each day. 

Sleep hygiene — a set of daily behaviors you can do each day — can not only help you meet your sleep need, it can help regulate your circadian rhythm.

In the study above, participants received just one sleep hygiene counseling session to help them get more sleep, which included discussing their sleep environment and bedtime habits. One important change? “Limiting the use of electronic devices before bedtime appeared as a key intervention,” said Tasali, the lead researcher on the study.

Here are other sleep hygiene behaviors you can do to help you keep your sleep debt low and stay in sync with your circadian rhythm: 

  • Keep a consistent sleep schedule: Wake up and go to sleep at the same times each day — even on weekends — to avoid social jet lag disrupting your circadian rhythm. 
  • Avoid caffeine, alcohol, exercise, and large meals too late in the day: These all make falling asleep harder and change the timing of your circadian rhythm.
  • Get light at the right times: Get bright light when you wake up and during the day, and then dim the lights and put on blue-light blocking glasses 90 minutes before bed. This will help you make enough of the sleep hormone melatonin to fall asleep, and research also shows bright morning light is linked to lower body weight.
  • Keep your bedroom cool, dark, and quiet: All three help you drift off more easily and stay asleep all night long. 

The RISE app can tell you the right time to do things such as get natural light, put on blue-light blocking glasses, and have your last coffee for the day, depending on your individual circadian rhythm.  

Focus on Your Sleep to Help You Lose Weight 

Eating right and exercising are what many of us think are the first steps you take when you’re trying to lose weight. But study after study has found sleep — including how much you get and at which times — can massively impact your weight. 

So, you can enhance your weight loss efforts by tuning into your sleep. To break the link between sleep deprivation and weight gain, the RISE app can calculate how much sleep debt you have and help you pay it back. The app can also predict your circadian rhythm each day, so you can work to be in sync with it, keeping everything from your metabolism to the hormones responsible for hunger in check. 

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Summary FAQs

Why is it so hard for me to lose weight?

Even with a good diet and exercise, it’s hard to lose weight if you’re not getting enough sleep or if your circadian rhythm is regularly disrupted.

Can’t seem to lose weight no matter what I do?

If you can’t lose weight despite diet and exercise, look at your sleep. Make sure you’re getting enough sleep each night and keeping a consistent schedule in line with your circadian rhythm. 

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