More and more studies are proving that the less we sleep, the higher out body fat levels will be, and the more we will weigh. It’s what many observational studies seem to show, and even a number of randomised controlled studies have supported this evidence. So, the stats and results are there to show that getting sleep can lead to an increase in weight, but exactly why does this happen? Recent research seems to offer some answers.
Brain scans of patients who are sleep deprived have shown an increase in the activity in response to food, in particular areas of the brain which are considered to be associated with reward, including the putamen, insula and nucleus accumbens. Research into other sections of the brain during sleep deprivation when exposed to pictures of food seem to suggest that these regions respond much more strongly than had they not been deprived of sleep.
It might be interesting to note that the similar regions of the brain respond in similar ways between obese patients and patients who are sleep deprived. A lot of recent evidence points in the direction that obese people may have significant differences in the brain than those of normal-weight people.
There is a common trend when it comes to the activity of the brain regions in response to food in sleep deprived people and obese patients. This connection is known as the “salience network”. The network keeps an inventory of how the body is as a whole, and then guides the behaviour of the body in order to put things right if something’s amiss. This system allows us to notice if something might be useful in our environment, and generates some of our impulse to act. It then gives us a small reward when we’ve acted and the desired result is achieved. It’s possible that sleep deprivation could activate the salience network and make particular types of food more appealing and palatable.
There is plenty of evidence which suggests that sleep deprivation and obesity could be directly linked. In one study carrying out research into this potential link, forty-six adults aged between 21 and 50 were recruited. None of the individuals were obese, but were between normal weight or slightly over-weight. All were non-smokers, and tested to ensure they had regular sleep patterns. The patients were given a baseline functional MRI (fMRI) of their brains after sleeping for up to nine hours. Their caloric and macronutrient intake was measured the following day.
Afterwards, the patients were then randomly assigned to either a total sleep deprivation (TSD) condition, or a control condition. Those participants in the TSD group were not allowed to sleep at all for one night. Both groups were then studied again for their macronutrient and caloric intake levels.
The primary focus of the fMRI’s were to measure the “resting state functional connectivity”. The resting rate is when the patients were having their brain scanned whilst doing nothing else. FMRI’s are sometimes conducted whilst patients are performing tasks, although this was not done so here “Functional connectivity” refers to studying how the activity in various parts of the brain are related.
The results of the test showed that the participants who were randomised to TSD didn’t actually different from the controls in any measurable amount, which included also their caloric and macronutrient intakes. This was a positive result, as it showed that any variation between them would be more likely attributable to sleep deprivation, as opposed to a statistical accident.
The results of the study showed that total sleep deprivation can, in the short-term, have an effect on the brain, which can change the macronutrient intake. Sleep deprivation, through this study, showed us that sleep deprivation increased caloric intake of almost 1000 calories on average. What we also learned from the study is that almost all of the extra caloric intake can be attributed to extra night time eating. The TSD group, when allowed a full night’s sleep, ate as many calories during the day as they did when they were deprived of sleep. However, most of the calories were consumed as fat, and fewer as carbs, when deprived of sleep.
This poses the question of why the TSD group ate more at night. Was it because of boredom? It might be a slight possibility, but they were allowed to do all types of other activities as they wished to prevent them from being bored. So, why did they decide to eat more food? Correlations could be made between variations in functional connectivity with macronutrient intake on the day following sleep deprivation.
This study wasn’t the first to conclude that sleep deprivation can cause an increase in caloric intake. A particular trial found a 500 per day calorie increase after patients were deprived of sleep, yet no further energy was expended in order to account for the surplus of caloric intake. Another trial demonstrated that the increased calories which are consumed as a result of sleep deprivation can be directly linked with gaining weight.
The idea of a lack of sleep being a contributing factor to weight gain and obesity has long being studied. A trial showed that an increase in energy and fat, particularly saturated fat that were consumed as a result of a lack of sleep could be linked to higher body fat levels.
The evidence is strong for linking sleep deprivation to individuals eating more, less healthy food, and therefore can be attributed to weight gain.