Poor sleep linked to sustained increases in dangerous visceral fat
Studies continue to demonstrate the importance of good sleeping habits in maintaining a healthy body weight, but there is still much to learn when it comes to understanding the finer details of this relationship. Researchers at the Mayo Clinic have shed new light on this topic by demonstrating how a lack of sleep can increase levels of insidious visceral fat deep in the abdomen, which carries acute risks to our health.
A long line of published research has illuminated the connection between poor sleep and obesity and its related conditions. This includes showing how irregular sleeping patterns can elevate our risk of hypertension and other metabolic disorders and double our risk of heart disease. Similarly, studies have shown how extra sleep can lead to calorie deficits and lower the obesity risk for newborns.
While scientific knowledge in this area is building, the Mayo Clinic researchers note that no studies have been carried out on body fat distribution specifically. Their work focuses on the differences between subcutaneous fat, the type beneath the skin you might feel when you pinch your belly, and visceral fat, the invisible type deep in the abdomen that can surround the liver, intestines and other organs.
Visceral fat only accounts for around 10 percent of the total body fat in most people, but when it builds up to surplus levels it can play a disproportionate role in adverse health outcomes. This is because it produces large amounts of chemicals linked to a wide variety of conditions including cardiovascular disease, cancers and asthma.
So, keeping levels of visceral fat in check is important, and the Mayo Clinic study was designed to explore how sleep may play a regulatory role. It involved 12 healthy subjects who were not obese, and placed in either a normal group sleeping nine hours a night or a restricted group sleeping just four hours a night for a period of two weeks. This came after acclimation periods and recovery periods of normal sleep, with the groups then swapping sleeping habits after a three-month washout period.
The groups had free access to food throughout, with the scientists tracking their energy intake, energy expenditure, body weight, biomarkers of appetite and fat distribution through CT scans. The subjects were seen to consume more than 300 extra calories a day during their sleep restriction periods, while their energy expenditure remained the same. This led to small weight gains but an 11-percent increase in visceral fat, according to the researchers.
"The visceral fat accumulation was only detected by CT scan and would otherwise have been missed, especially since the increase in weight was quite modest – only about a pound," said Dr Naima Covassin, who led the study. "Measures of weight alone would be falsely reassuring in terms of the health consequences of inadequate sleep.
The study was designed to replicate the irregular sleeping patterns shift workers might endure, with periods of inadequate sleep interspersed with periods of normal rest. Importantly, the scientists found the impacts on visceral fat appeared to persist beyond the periods of insufficient sleep even when body weight decreased, which could have cumulative effects if these sleeping patterns take place over a number of years.
"Normally, fat is preferentially deposited subcutaneously or under the skin," said Virend Somers, principal investigator of the study. "However, the inadequate sleep appears to redirect fat to the more dangerous visceral compartment. Importantly, although during recovery sleep there was a decrease in calorie intake and weight, visceral fat continued to increase. This suggests that inadequate sleep is a previously unrecognized trigger for visceral fat deposition, and that catch-up sleep, at least in the short term, does not reverse the visceral fat accumulation."
The research was published in the Journal of the American College of Cardiology.
Source: Mayo Clinic