We are currently facing a major obesity pandemic. Most alarming is the accelerated increase in overweight and obesity in children, with childhood obesity tracking into adulthood. Although there is a strong genetic contribution to obesity, the current pandemic has been driven by environmental factors. Unfortunately, interventions aiming to alter food selection (eg, less fat and sugar) and calorie intake (eg, smaller portions) and to increase physical activity have not been able to result in long-term weight loss and maintenance. These approaches are confounded by the fact that only an insignificant daily energy surplus could result in obesity over time. Although changes in the basic balance between energy intake (food calories) and expenditure (physical activity) are obviously responsible for the current obesity pandemic, our understanding of the factors that alter this balance remains incomplete. Intriguingly, sleep may be a factor that alters both sides of the energy balance equation. The precise physiological functions of sleep are unknown, but the contribution of sleep to physical and psychological health, and its social and economic significance, is increasingly recognised.¹ Sleep research has mainly concentrated on the cognitive consequences of sleep loss, on the basis of the belief that sleep is for the brain alone. Recently, however, there has been a shift in interest in the consequences of sleep loss for other organs and several physiological systems. Also, more laboratory studies on sleep are now concentrating on investigating the health and performance effects of chronic partial sleep restriction, which is truer of real life, rather than acute total sleep deprivation. On …