Insulin sensitivity: One night of poor sleep could equal six months on a high-fat diet, study in dogs suggests

When the body becomes less sensitive to insulin (i.e., "insulin resistant"), it needs to produce more insulin to keep blood sugar stable. This may eventually lead to Type 2 diabetes, a disease where the body's insulin response doesn't work properly and there is too much sugar in the blood. Diabetes is associated with a number of serious complications, including heart disease. Individuals with obesity are more likely to develop insulin resistance and subsequently, diabetes.

"Research has shown that sleep deficiency and a high-fat diet both lead to impaired insulin sensitivity, but it was previously unknown which leads to more severe insulin resistance," said Dr. Broussard. "Our study suggests that one night of total sleep deprivation may be as detrimental to insulin sensitivity as six months on a high-fat diet. This research demonstrates the importance of adequate sleep in maintaining blood sugar levels and reducing risk for metabolic diseases like obesity and diabetes."

To conduct the study, the researchers measured insulin sensitivity in eight male dogs before and after diet-induced obesity. Prior to the high-fat feeding, researchers used an IV glucose tolerance test to measure insulin sensitivity in dogs that had one night of sleep deprivation, and compared results to dogs that had a normal night's sleep. The dogs were then fed a high-fat diet for six months, at which point they were tested again. Prior to the high-fat diet, one night of sleep deprivation reduced insulin sensitivity by 33%; this reduction was similar to the reduction caused by a high-fat diet alone (21%). Once the dogs had impaired insulin sensitivity from the high-fat diet, one night of sleep deprivation did not further impair the insulin sensitivity.

"One night of sleep deprivation and six months of a high-fat diet both reduced insulin sensitivity by a similar degree in canines; however, there was no additive effect of sleep loss and high-fat diet," continued Dr. Broussard. "This may suggest a similar mechanism by which both insufficient sleep and a high-fat diet induce insulin resistance. It could also mean that after high-fat feeding, insulin sensitivity cannot be reduced further by sleep loss."

In addition to impaired insulin sensitivity, sleep deprivation can lead to increased food intake and overall increased risk for metabolic diseases.

"It is critical for health practitioners to emphasize the importance of sleep to their patients," said Caroline M. Apovian, MD, FACP, FACN, a Fellow and spokesperson for The Obesity Society. "Many patients understand the importance of a balanced diet, but they might not have a clear idea of how critical sleep is to maintaining equilibrium in the body."

According to Dr. Broussard, future research should examine the pathways that may account for the interactions between sleep and diet and their relationship to insulin sensitivity. It will also be important to determine whether insulin sensitivity is improved after recovery sleep, which is beginning to be addressed in clinical studies.

These types of basic science studies and canine models are critical in helping to understand the causes and complications of obesity and to identify mechanisms that lead to its prevention or cure.