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Diet and lifestyle

Lack of sleep can make you fat

Not being able to get a decent night’s sleep is bad enough, but now Swedish-German research collaboration has added a new misery to the list of illnesses you risk developing by not sleeping enough. In addition to harmful effects on brain functioning, the new research reveals that, because of changes in the gut flora, people have higher risks risk of obesity and type 2 diabetes after just a few days without high-quality sleep.


The research was carried out in a sleep laboratory with the same group of participants – first two nights with 4 hours of sleep and then two nights with 8.5 hours. The participants provided a faeces sample and took an oral glucose tolerance test after each night.

The gut flora of the participants changed considerably. Following the nights with less sleep, they had many more Firmicutes bacteria than Bacteroidetes bacteria. These changes are a clear sign of metabolic disturbances and very undesirable, because they are a factor promoting obesity. The participants also had elevated levels of three other types of bacteria with the same known effects.

In addition to an increased number of obesity-causing bacteria, the participants’ glucose tolerance tests showed reduced insulin sensitivity, which people with type 2 diabetes usually have. In the past two decades, research has revealed the increasingly important role of human gut flora – or microbiota – on health. Previous studies on mice have shown, among other things, that mice that had the gut microbiota transplanted from a fat mouse became more obese.

Nevertheless, this is the first time research has so clearly demonstrated that lack of sleep can change the flora of the human gut and thereby help to promote metabolic disturbances. Once again, this research emphasizes the importance of high-quality sleep.

“Gut microbiota and glucometabolic alterations in response to recurrent partial sleep deprivation in normal-weight young individuals” has been published in Molecular Metabolism. In 2014, the Novo Nordisk Foundation awarded a grant to a co-author of the article, Christian Benedict, for the project Role of the Fat Mass and Obesity Gene for Sleep Loss Related Health Consequences in Humans.