Energy balance: a crucial issue for exercise and sports medicine

The recently published issue of British Journal of Sports Medicine (http://bjsm.bmj.com/content/49/4.toc) includes articles on several important topics in exercise science and sports medicine. We are grateful to the many leading clinicians and scientists who have made these contributions. This editorial will address another relevant topic that requires focused attention—energy balance. Non-communicable chronic diseases (NCDs), such as cardiovascular disease, cancer, obesity and type 2 diabetes, are clearly the leading public health problems facing the world in the 21st century.1 The causes of NCDs are predominately unhealthful lifestyles such as physical inactivity, poor diets, smoking, unhealthful sleep habits and not managing stress effectively.1 In recent years, obesity rates have increased in most countries, and this problem receives enormous attention, in both the popular media and scientific press. The fundamental cause of increasing rates of obesity is too many people being in a positive energy balance on too many days; but the problem is very complex.2 From a simple perspective, energy balance is the ratio of energy intake and energy expenditure, and if more calories are consumed than are expended, a person will be in positive energy balance. This excessive energy will be stored in the body, mostly as body fat. Of course maintaining energy balance is a much more complex issue than this simple statement, with numerous environmental, social and physiological factors having a role. Extensive reviews of the energy balance concept have been published in recent years.3 ,4 …