Practicing good sleep hygiene and meeting your individual sleep requirement every night is essential for a healthy lifestyle. It is also important for maintaining your weight. This is because the quantity and quality of sleep influences the hormonal activity that regulates appetite.
Sleep deprivation and poor sleep habits can disrupt this careful balance, greatly increasing your chance of gaining weight; it can even put you at risk for obesity.
The linking factor
The University of Warwick Medical School found a correlation between short sleep, a higher body-mass index [BMI] and a larger waist circumference.
Furthermore, researchers at Columbia and the University of Chicago found that people who sleep five hours per night have a 50 per cent higher chance of being obese, while those who sleep six hours have a 23 per cent greater risk of obesity than their well-rested counterparts.
The correlation goes both ways—those who are obese often have difficulty sleeping due to the discomfort. They also have medical problems such as sleep apnoea.
The excess weight around the neck complicates respiratory functioning, causing heavy snoring, repetitive pauses in breathing, a high risk for hypertension and excessive day-time sleepiness.
We know that sleep and food are both related to our feeling energetic, but why this strong connection between amount of sleep at night and body weight?
The role of hormones
Many scientists have looked at hormones to get to the bottom of this relationship. How much we eat for energy is largely dictated by the interplay between two hormones: ghrelin and leptin.
In humans, ghrelin concentrations are negatively correlated with body mass index [BMI]; the higher the BMI, the lesser ghrelin circulating in the blood. This makes sense: the more energy you already have stored, the less your body needs you to eat.
Therefore, as Troels Hansen of Aarhus University Hospital in Denmark and his colleagues have discovered, obese patients [typically characterised by lower than average levels of ghrelin] saw an increase in ghrelin levels by 12 per cent following weight loss interventions.
Leptin, on the other hand, inhibits food intake. It is produced mostly in adipose tissue [another name for body fat], where it is released into the bloodstream and heads to the brain to report on how much energy the body is storing.
While ghrelin makes you hungry, leptin helps with weight loss in the long term, making you less hungry. Leptin levels are higher among those with a higher BMI and among those with a higher percentage of total body fat.
Researchers Shahrad Taheri and Ling Lin from the Howard Hughes Medical Institute at Stanford University, USA, and their colleagues found that shorter sleep is associated with elevated ghrelin and reduced leptin and, of course, higher BMI.
This imbalance increases appetite and slows metabolism. A study by researchers at Stanford and the University of Wisconsin monitored the sleep duration, weight, body fat, and leptin and ghrelin levels of 1,000 volunteers. They found that those who slept less than eight hours at night had elevated ghrelin and lowered leptin molecules and, alarmingly, higher body fat.
Still not convinced? Consider this: Researchers at the University of Chicago determined that even among healthy men and women with average BMIs, those who slept less than six hours per night experienced hormonal changes that could affect their future body weight and overall health.
This is because short-sleepers produce 30 per cent more insulin than normal sleepers in order to maintain regular blood-sugar levels, predisposing them to weight gain.
Another important factor to consider is sleep and cortisol levels, also known as stress hormones: Insufficient sleep triggers the release of additional cortisol, which also stimulates hunger.
When sleep deprived, we crave sugary and high-calorie foods. In one study of 12 healthy males, researchers at the University of Chicago found that when people were subjected to sleep deprivation, not only did their leptin levels go down and ghrelin levels sky-rocket, but their cravings for high carbohydrate, calorie-dense foods also increased by 45 per cent.
There are, of course, various factors [stress, diet, exercise, and genetics]—all out of our control—that contribute to our body shapes and sizes and our appetites. However, for many of us, instead of a snack, we may actually need some shuteye.
Once you understand this, you can begin to use sleep to control and even lose weight. Overall, it's clear: sleep is crucial to regulating your appetite and metabolism and plays a key role in any healthy weight management programme.
In addition to practicing good sleep habits [such as meeting your nightly requirement of 7.5 – 8.5 hours of sleep and maintaining a regular sleep/wake schedule]; following a well-balanced diet will significantly improve your sleep. In doing so, you'll improve your ability to maintain your weight and also live a healthy lifestyle!
Tips for sleep and weight management
- Eat most of your calories during the morning and early afternoon and majority of your calories, particularly proteins, before the evening. Have a light meal at dinner and save room for a light, pre-bed snack.
- Eat a dinner of grains and vegetables. Choose a light, satisfying meal of hearty leafy green vegetables such as spinach or fenugreek and rice or easy-to-digest vegetables.
- Avoid all caffeine after 2pm.
- Enjoy a light snack 45 minutes before bed. Choose foods containing L-tryptophan as they are useful for promoting sleep due to their serotonin-inducing properties [serotonin is the neurotransmitter involved in initiating sleep]. Simple, easy-to-digest carbohydrates such as crackers, half a banana, or a handful of non-sugary cereal are best.
- Avoid large meals and spicy foods before bedtime. These will increase gastrointestinal activity and disrupt sleep.
With inputs from Rebecca G Fortgang and Sharon R Driscoll. Rebecca G. Fortgang is a BA with honors in linguistics and cognitive science from Cornell University. Sharon R Driscoll is a pre-medical student at Cornell University and a member of the Sleep for Success consulting firm.
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