The Impact of Sleep on Metabolism and Weight
By Dr Helmi Ismail, Medical Advisor of PMCare
This is written during the typical days of Ramadhan. The work is occasionally slowed down by drowsiness due to lack of sleep. Sleep deprivation results from waking up for the pre-dawn meal without complementing adjustment to going-to-bed time. Anyone with a similar experience would be as disruptive. This alone highlights the importance of sleep.
Understanding Sleep and Duration
Sleep is a natural and temporary state of rest that happens in cycles. During sleep, you’re not awake and unaware of your surroundings. It usually involves lying down with your eyes closed, dreaming, and changes in brain activity and body functions. Sleep has two main stages: non-REM and REM sleep. It is considered essential to the restoration and recovery of vital bodily and mental functions.
The need for sleep varies with age as shown in this chart.
Newborn sleeps anything from 15 – 18 hours in a day. As the baby grows the duration of sleep slowly decreases to 14 – 16 hours up to about 6 months, and about 9 – 12 hours towards the end of his/her first year. The sleep duration is broken up into hours of nighttime, daytime, and naps in between. The amount of sleep is considered to be vital for both external physical growth and internal organ development and function.
Beyond this age, the need generally reduces further to stabilize to 7 – 9 hours. The. range is taking into consideration three is a biological variation in terms of need within the same age level.
The Quality of Sleep
Getting enough sleep is important, but the quality of sleep matters just as much. While sleep studies can measure sleep patterns—like having more deep sleep early in the night, more REM sleep later, and fewer wake-ups—what really counts is how rested you feel. Even if the data shows a “good” night of sleep, it’s still considered poor if you wake up feeling tired or unsatisfied. That’s why sleep quality is often based on personal experience rather than just numbers.
Sleep affecting Appetite and Satiety
Sleep plays a key role in controlling hunger by regulating two important hormones: leptin and ghrelin. Leptin, produced by fat cells, signals when you’re full, while ghrelin, from the stomach, stimulates hunger. When you don’t get enough sleep, this balance is thrown off—one study found that just two nights of only 4 hours of sleep increased hunger-boosting ghrelin by 28% and lowered fullness-signaling leptin by 18%, leading to stronger cravings for high-calorie foods.
Another study in 2016 showed that sleep-deprived people ate an extra 385 calories per day. Poor sleep also raises cortisol, the stress hormone, which encourages fat storage and makes it harder for the body to regulate blood sugar, increasing the risk of weight gain and metabolic issues.
Sleep affecting Glucose Metabolism including Insulin Sensitivity
Sleep quality crucially affects glucose processing. During deep sleep, the body repairs tissues and regulates insulin, the hormone that helps the body absorb and use sugar for energy. Sleep deprivation makes the body less responsive to insulin. In one study, healthy adults who slept only 4.5 hours per night for four days had a 40% drop in insulin sensitivity.
This insulin resistance is similar to early-stage type 2 diabetes, leading to higher blood sugar levels. Research also shows that regularly sleeping less than 6 hours a night can increase the risk of developing type 2 diabetes by 30% over ten years.
Sleep and Disruption of Circadian Rhythm
The body’s circadian rhythm, a natural 24-hour internal clock, helps regulate metabolism based on environmental cues like light.
Shift workers, whose schedules often disrupt this rhythm, have a higher risk of metabolic syndrome—a group of conditions like high blood pressure and high blood sugar. Studies show that irregular sleep patterns interfere with genes that control metabolism, affecting how the body processes sugar and fats. Eating late at night, which is common among shift workers, makes things worse by throwing off the body’s natural ability to manage glucose, leading to poor metabolic health.
Sleep influencing Energy Expenditure and Physical Activity
Sleep affects energy balance—calories consumed versus burned. While metabolism slows down during sleep, not getting enough sleep actually makes the body burn 5–20% fewer calories overall because it tries to conserve energy. Lack of sleep also causes fatigue, leading to less physical activity. One study found that sleep-deprived people burned fewer calories and felt more tired, causing them to consume 385 extra calories per day. This imbalance, sustained over time, can result in significant weight gain, illustrating sleep’s role in weight management.
Long-Term Health Consequences, particularly obesity and other health risks
Chronic sleep deprivation fosters obesity, diabetes, and cardiovascular diseases. A 10-year study correlated short sleep duration with a 55% higher obesity risk in adults. Excess weight, especially belly fat, leads to inflammation and makes the body less responsive to insulin, worsening metabolic problems. Poor sleep further increases the risk of cardiovascular disease by raising blood pressure and LDL cholesterol (often called “bad cholesterol”), creating a vicious cycle of metabolic and cardiovascular decline. Thus, sleep well to lose weight!
Checklist for Getting a Good Night’s Sleep
Sleep’s profound impact on metabolism underscores its role as a pillar of health. By regulating hormones, glucose metabolism, circadian rhythms, and energy balance, adequate sleep prevents metabolic disorders. Public health initiatives should prioritize sleep education, advocating for 7–9 hours nightly to mitigate obesity and diabetes epidemics. In embracing sleep’s restorative power, individuals can harness a natural, potent tool for metabolic health, fostering vitality and longevity.
References
- Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Science Translational Medicine (2012).
- Insufficient sleep undermines dietary efforts to reduce adiposity, Annals of Internal Medicine (2009).
- Leptin and ghrelin levels during sleep restriction. The Journal of Clinical Endocrinology & Metabolism (2004)
- Sleep and Metabolism: An Overview, International Journal of Endocrinology (2010)