Insufficient sleep and circadian misalignment are novel risk factors for the development of metabolic diseases and are often unavoidable in modern, 24-hour society. Over the last century, the average sleep duration has decreased while obesity and diabetes are on the rise. Insufficient sleep leads to insulin resistance—the biggest risk factor for the development of diabetes—yet we have very little understanding of how this occurs. In addition, women are more likely to suffer from poor sleep quality and more sleep disturbances, and this becomes even worse after menopause. My proposed study will examine insulin sensitivity in muscle and fat tissue before and after insufficient sleep in a group of men and women. Understanding the role of sex differences during insufficient sleep could help define better countermeasures and/or therapeutic targets to reduce the risk of obesity and diabetes when sleep loss is unavoidable.