Sleeping fewer than 8 hours a night linked to beer belly risk

People who do not get enough sleep every night are more likely to suffer a pot belly, a new study suggests. 

The excess fat that accumulates around the torso and surrounds vital organs is called visceral fat — and it contributes to a beer belly and an undesirable apple body shape.

An international team of scientists gathered health data from more than 5,000 adults – half male, half female, who participated in two rounds of the US National Health and Nutrition Examination Survey in 2011 and 2013. Participants rated their sleep from one hour to 12.

The average age of participants was about 37 years and the average amount of sleep they got was a little less than seven hours.  One less hour of sleep, seven to eight hours being the goal, was tied to an overall increase of about 12 grams of visceral fat mass.

Visceral fat is the most dangerous type, leaking fatty acids into the bloodstream. It differs from the less dangerous subcutaneous fat that accumulates just below the skin’s surface and is responsible for wobbly fat and cellulite.

Subcutaneous fat (left) is more visible outside of the body, padding the outer layers of muscle just underneath the skin. People with more of this fat will have a ‘pear-shaped’ body. People with more visceral fat (right), which is more dangerous but less noticeable, are at an increased risk of many metabolic diseases 

Getting too little sleep leads to abnormal regulation of activity in different parts of the brain that affect the reward center, sleep, and appetite, which may explain the link between sleep deprivation and visceral body fat storage. 

Insufficient sleep leads to insulin resistance, which many scientists have suggested is linked to high visceral fat. 

Too much visceral fat is more likely to raise one’s risk of serious metabolic conditions that include high blood pressure, obesity, high cholesterol and insulin resistance, all of which raise one’s risk of heart disease, stroke, and type 2 diabetes.

It adds to a rich body of research pointing to the link between sleep, excess fat, and weight gain. The team noted that theirs is the first study to give a comprehensive view of how sleep duration affects fat storage in different regions of the body.

Dr Panagiotis Giannos said: ‘Our study adds to emerging evidence suggesting a prominent link between sleep deprivation and weight gain, which could be clinically significant, as visceral adiposity is associated with metabolic issues such as insulin resistance, type 2 diabetes and cardiovascular disease.’ 

Sleep deprivation is believed to cause a simultaneous decrease in leptin – the hormone that decreases the appetite – and an increase in the hormone ghrelin, which signals to the brain that it’s time to eat. 

It also causes the orexin system, which affects food intake and sleep patterns, to go haywire. This, the researchers suggest, could explain higher caloric intake and subsequent weight gain as a result of sleep restriction.

The study, published in the journal Sleep Medicine, used data from two US-led Health and Nutrition Examination Surveys conducted in 2011–2012 and 2013–2014 reflecting a total of 5,151 people aged 18 to 59.

The team of scientists used x-ray imaging to calculate people’s regional body fat percentages and sent them home with questionnaires asking how much sleep on a scale from one to 12, with one indicating just one hour of sleep and 12 indicating at least 12 hours of sleep. 

The average amount of sleep among the study subjects was slightly under seven hours. The researchers also revealed that the benefit of sleep duration plateaued at eight hours.   

Last spring, researchers from the Mayo Clinic studied how restricted sleep combined with free access to food drives up calorie consumption and consequently fat accumulation, especially unhealthy belly fat, in 12 healthy subjects.

A lack of sufficient sleep led to a nine percent increase in total abdominal fat area and an 11 percent increase in abdominal visceral fat, compared to the control group.

In 2019, a team of scientists from Pennsylvania State University reported that restricting sleep for just a few days per week alters how our bodies metabolize fats and changes how satisfied one feels after a meal.

The study involved 15 healthy men in their 20s who slept for a week at home for about 10 hours per night followed by 10 days of staying in a suite in the Clinical Research Center at Penn State where they were fed calorie-rich meals and slept for no more than five hours per night for four consecutive nights.

Sleep restriction led to higher insulin levels, changing how the body metabolizes fat.

Despite the importance of getting enough sleep for mental and physical well-being, over a third of Americans fail to do so on a regular basis. The Centers for Disease Control and Prevention and other public health experts recommend adults get at least seven hours of sleep per night.

For as many as 70 million Americans, that’s easier said than done. Roughly that many people have a sleep disorder that causes chronic sleep deprivation and negatively impacts a person’s quality of life. Some of those conditions include chronic insomnia,sleep-wake cycle disorders that push the body’s internal clock out of whack, sleep walking, and sleep apnea.