The Surprising Truth About Sleep and Weight Loss

Poor sleep quality, which is associated with overall sleep loss, is a very common complaint (1).

In 2014 a USA survey (TheSleep Health Index) found 45% of Americans reported that poor or insufficient sleep had affected their daily activities at least once in the previous 7 days. 35% of Americans reported “poor” or “only fair” sleep quality. 67% of the people with less than good sleep quality also reported “poor” or “only fair” health quality. High stress and low life satisfaction were also related to poor sleep quality.

There is a substantial body of research pointing to lack of sleep as a risk factor in the development of obesity, diabetes and general metabolic disorders (3, 4, 5, 6, 7).

Habitual short sleep has been associated with increased body mass index (BMI) in large population samples (8).

Sleep debt leads to sleep patterns generally associated with ageing and sometimes with depression, and is likely to increase severity of depression and risk of obesity and chronic age-related disorders (8).

Short sleep over time is also associated with higher mortality levels (7).

Lack of sleep leads to a decrease of ghrelin in the body leading to increased feelings of hunger (9) and desire for fatty foods.

In one study lack of sleep led to eating as much as 300 calories extra with people choosing snacks with around 50% more calories and twice the fat of snacks chosen by people who had enough sleep (7).

This same study suggested that besides increasing hunger and the desire for high calorie, fatty foods and reducing your ability to control your response to food, lack of sleep may also increase your hedonic drive for these foods.

In one small study having 5.5 hours sleep lead to up 55% less weight being lost as fat and increased the loss of fat free body mass by 60% compared to having 8.5 hours sleep (1).

There is also increasing recognition of a link between diet and the quality of sleep (8). A 2016 study found that a single day of a high fat and high sugar diet disturbed sleep. Participants took longer to fall asleep and then had less slow wave sleep which is associated with good sleep quality. Conversely a high fibre, low fat and sugar diet was associated with falling asleep faster and with more slow wave sleep (9).

Psychosocial (work and life) stress can lead to poor sleep in quality and duration (10), and insufficient and poor sleep is associated with weight gain( 11), so sleep, diet and stress are interrelated.

By understanding that sleep, diet and stress are interwoven we can work to address them all at once, by eating a healthier diet, taking steps to get better sleep and deploying tactics to reduce stress in everyday life.

Here's some science based tips to get a better night’s sleep:

Limit the amount of alcohol you drink

Although alcohol consumption may help you fall asleep faster, alcohol can disturb your REM cycle making you toss and turn, when you should be in your deepest sleep (12).

Exercise

Exercise has long been associated with better sleep (13) . You may need to exercise consistently for up to 4 months for the full beneficial effects to kick in, especially if you have chronic sleep problems (14), although some studies have found modest sleep improvements after a single day of exercise (15).

I have seen some claims that you shouldn’t exercise just before bedtime, but found one study that contradicted that with young adults experiencing improved sleep after exercising just before bed (16).

In a survey of over 34,000 people in North America, 55% of people who practiced yoga reported better sleep, and 85% reported it reduced stress. 19. Various studies suggest yoga improves sleep quality and duration (20, 21, 22).

Cut the caffeine hit 6 hours before bedtime

Studies have shown that a cup of coffee up to 6 hours before bedtime has a significant effect on sleep disturbance. (17). In one study caffeine was found to decrease total sleep time by up to 2 hours, increase wakefulness and significantly disturb sleep quality (18).

Less screen time before bed

Technology use (TV watching, cell phone use, video gaming, listening to music, social networking and telephone use) at bedtime is associated with significant adverse effects on a whole range of sleep parameters according to a UK study(18).

Exposure to short wave blue light, such as we get from our tablets and mobile devices has been shown to significantly reduce the duration of sleep and disrupt the continuity of sleep (18). In one study exposure to a strong blue light before sleeping lead to an average of 7.6 awakenings compared to a normal average of 4.5 awakenings (19).

Interactive screen time (cell phones, games consoles, laptops as oppose to TVs) in the hour before bed is associated with more difficulties falling asleep and with unrefreshing sleep (20). The same survey reported that 9 out of 10 Americans used a technological device in the hour before bed, although under 30 were more likely to be using interactive technology.

Using a red filter over your screen can reduce the effect of the short wave blue light, but of course cannot change your unconscious responses to interactive technology.

Keep to a sleeping routine

Disruptions to the natural circadian rhythm of the body which regulates waking and sleeping times are interrelated with sleep deprivation, obesity, diabetes and increase the risk of cardiovascular disease (21, 22, 23).

The work and social commitments associated with our modern lives mean during a working week we often wake before the end of our circadian sleep rhythm is reached and generally do not fall asleep until after the window opens in the evening leading to a “social jetlag”. This restricted sleep means we may sleep for longer at weekends/ non-work days (23). This social jetlag is associated with increasing BMI (24).

One New Zealand study found that even a 2 hour difference between weekday and weekend sleeping schedules was associated with higher BMI, in comparison to people with no social jetlag (25).

By keeping to routine sleeping schedules which allow enough sleeping time every day it should be possible to minimise or eliminate this social jetlag effect and thereby reduce or remove the chance of any associated weight gain.

Light exposure, sleep and fat loss

Exposure to natural morning light for 45 minutes in the morning for 3 weeks resulted in reduced body fat and appetite for a study group of obese women, and that wasn’t related to differences in photoperiod (25).

In another study exposure to bright lights for a group of obese women lead to reductions in body mass index (26). Morning light exposure was found to have significant effects on ghrelin and leptin levels which associated with appetite and hunger, especially for sleep deprived individuals (27).