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The Sleep Loss and Weight Gain Connection

Updated December 12, 2023.

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In the United States – and elsewhere in the world, too – a long, restful night of sleep is becoming a thing of the past. Maybe that doesn’t come as too much of a surprise, though – what with phone notifications dinging at all hours, the constant wail of sirens in sprawling metros, pressing deadlines in a fast-paced business environment, and the omnipresent glow of digital screens. As one pair of researchers observed: “Ours is a 24-h society with more evening and night-time work and leisure activities.”

Ours is also a sleep deprived society. In fact, if you were an adult living in America in 1960, you’d get an average of 8 and a half hours of sleep every night. Compare that to 2008, when American adults were averaging only 6 hours and 40 minutes of sleep per night! That’s an alarming trend because chronic sleep loss can be quite destructive to one’s health.

Obviously, slogging your way through the day – because you didn’t get enough sleep the previous night – is no fun. Your productivity might suffer if you’re chronically low on sleep, and your powers of concentration could go out the window.

But there are other possible consequences of not getting enough sleep – and over the long-term, regular sleep loss can exact a terrible toll on your body.

One such toll, for example?

An increased risk of weight gain. If you’re not getting ample sleep, then you might be less-than-pleased with the number you see when you step on the scale. So if you’re striving to maintain a healthy weight, make sleep a top priority!

But why is this the case – why is sleep so important for effective weight management?

One big reason why: sleep has a powerful influence on your body’s hormones, many of which affect your weight – like the “hunger hormone.”

Sleep and the "Hunger Hormone"

To remain at a constant, healthy weight, you must burn off the same amount of energy that you take in from food. You need an energy balance, in other words. Fortunately, the body has mechanisms in place – including two key hormones – that help maintain this energy balance.

The first of these hormones is leptin. Produced mostly by your body’s fat cells, leptin has the job of suppressing your appetite. It is a chemical signal – released into your bloodstream and sent to your brain (it crosses the blood-brain barrier) – that tells your body when it has consumed enough food to meet its energy requirements. For example, in healthy humans, overeating boosts leptin levels – one reason why your appetite for a slice of pumpkin pie might diminish as soon as you’ve eaten a hefty Thanksgiving dinner. On the other hand, if you go on a fast, your leptin levels will plummet – dramatically increasing your appetite.

Then there’s ghrelin, another hormone involved in maintaining the body’s energy balance. In many ways, ghrelin is the complete opposite of leptin – intensifying your appetite and telling your body that more food is needed. The feeling you know as “hunger” is partially caused by elevated levels of ghrelin – motivating you to reach for the nearest snack or cook up a tasty meal. (Hence why ghrelin has been nicknamed “the hunger hormone.”)

How does all this tie in with sleep? As it turns out, several studies have found that less-than-adequate amounts of sleep are linked with low levels of leptin and high levels of ghrelin. So if you don’t catch enough shut-eye, you might feel hungrier throughout the day – prompting you to eat more. This, in turn, can result in weight gain.

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Many sleep-deprived people counter this uptick in hunger by constant snacking. However, most convenient pre-packaged snacks are often high in fat and low in protein – further contributing to weight gain. So if you do have to forgo sleep, then at least try to choose healthy foods to munch on (like fruits, veggies, and protein-packed foods)!

Sleep and Cortisol

Cortisol is a hormone that allows your body respond to stress and danger. It’s also what helps wake you up in the morning after a good night of sleep, because cortisol levels in the blood don’t stay the same throughout a given 24 hour period. Instead, your cortisol levels rise and fall in a rhythmic pattern (known as a circadian rhythm or circadian cycle).

Typically, in healthy humans, cortisol levels are highest in the morning – then gradually descend. Cortisol levels are low in the evening, allowing you to feel a little drowsy and in the mood to rest. Cortisol levels continue dropping late into the night, before climbing again early in the morning.

Inadequate amounts of sleep, however, disrupts this natural cycle: scientists have discovered that insufficient sleep elevates cortisol levels. And while elevated cortisol levels are desirable when you’re confronting a sudden danger, chronically high levels of cortisol are far from beneficial.

Cortisol, you see, is responsible for activating the fight-or-flight response – stimulating you with a rush of energy when there’s a threatening situation. Cortisol gives you this sudden energy by turning some of the protein in your muscles into glucose (or sugar).

Excess glucose is converted to fat, so if your cortisol levels are consistently high, you might lose muscle and gain more fat – and put on more weight. In short, inadequate sleep leads to an increased state of stress (indicated by higher cortisol levels) – and, over time, this can harm your body, stripping you of muscle and making it difficult to maintain a healthy weight.


Sleep loss can disrupt your hormonal balance and result in weight gain – so if you’re aiming to effectively manage your weight, try to catch enough snooze time every night.

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