By Rob Henst at SSISA Sleep Science in collaboration with MySleep
Are you trying to lose weight by eating more healthy and exercising more? Great! But chances are you are ignoring another important aspect of weight loss: sleep!
A lot of research has been done towards the relationship between poor sleep and gaining weight. For example, one study has shown that adults who sleep less than 5 hours per night have a 55% higher risk of being obese. The relationship does not only apply to adults; even children who sleep less than 10 hours per night have a 89% higher risk of obesity. Another study has shown that obese adults generally sleep 1.5 hours less than lean adults, and lean men who sleep less than 5 hours each night have a 91% higher chance of becoming overweight than those who slept more than 5 hours. Finally, elderly women who slept less than 5 hours each night had a whopping 241% greater risk of gaining 5 kg in just two years than those who slept more than 5 hours. These studies are just the tip of the iceberg, and present a clear message: sleep cannot be ignored in the fight against weight gain.
Let’s take a look at why sleep is so important for losing weight. Sleep is the foundation of a healthy individual: it is important for our immune system to work well, for our brain and cognitive performance to stay optimal, and for our body to recover from injury and illness. Moreover, sleep helps us control our hormone levels that regulate our energy balance.
Two hormones that are specifically important in the development of obesity are leptin and ghrelin. Leptin decreases appetite, while ghrelin increases appetite. These hormones are important for maintaining a healthy energy intake. However, even after just one night of poor sleep, the leptin levels decrease, and the levels of ghrelin significantly increase, which causes an increased feeling of hunger. Being hungry in a world where food is available on every streetcorner is not going to help a person stay lean or lose weight. Because poor sleep also affects our decision making abilities, we may be more likely to opt for an unhealthy snack as opposed to something more healthy when we get hungry.
Melatonin and Thyroid-Stimulating Hormone, or TSH for short, are two other hormones that play an important role in weight gain. Melatonin is also called the “dark hormone” as its production is suppressed by light, and peaks at night. Short-sleeping individuals may be exposed to more light at night, and thus their melatonin levels are suppressed. As a consequence, the reduction in insulin secretion leads to elevated blood glucose, which may result in weight gain, insulin resistance and diabetes. TSH stimulates the production of two other hormones; T3 and T4, which helps your body with energy metabolism. However, poor sleep decreases the production of TSH, which leads to the reduction in T3 and T4 hormones, and an altered metabolism. Thus, as a result of poor sleep, your metabolism or energy expenditure will decrease. Studies have also shown that after just one night of poor sleep, a person is more likely to be physically inactive, decreasing the energy expenditure even further. Poor sleep also results in our body utilising more carbohydrates and less fat, which may also lead to weight gain, insulin resistance and diabetes.
The relationship between poor sleep and obesity goes two ways: we have already mentioned how poor sleep can lead to weight gain and obesity, but weight gain or obesity can also lead to poor sleep. For example, people with excessive body weight are more likely to experience depression and stress, which are both known to influence sleep and cause insomnia. But lifestyle factors that are often associated with living with excessive body weight such as poor eating habits and lack of physical activity also have a negative effect on sleep. People with increased body weight are also more likely to have obstructive sleep apnea, a very common sleep disorder among people with a body mass index (BMI) over 30 kg/m2. People with obstructive sleep apnea partly or completely stop breathing during sleep. The blood oxygen levels decrease as a result of the sleep apnea, and when the brain notices that something is wrong, the person is woken up often gasping for air. He or she would then start breathing again and fall back to sleep. This cycle then keeps repeating itself throughout the night. As a result, someone with sleep apnea may feel as though they sleep the whole night, but remain feeling tired as if they had no sleep at all. People with sleep apnea often increase their body weight even further, because of the disruptive effects on sleep.
If you are trying to lose weight, it is important to make sure you are getting between 7 and 9 hours of sleep each night and that your sleep is not being disrupted by insomnia or sleep apnea. Visit www.sleepscience.co.za for more information on how you can improve your sleep, or visit www.mysleep.co.za to find out your risk for sleep apnea.