Making progress on the global crisis of obesity and weight management

Food and obesity are undoubtedly linked but the relation is complex. Michael Lean and colleagues discuss what we know, and what we don’t know, about weight management Obesity is an unsolved crisis, generating long term distress and disabilities, reducing human capital, and increasing disease burdens and healthcare costs globally. Obesity has a complex aetiology, incurring controversies within both scientific and media arenas.1 Poor education and socioeconomic situations are important drivers of severe obesity, confounding country analyses by racial or ethnic groups. Data collected by EUROSTAT show wide variations in prevalences of people with a body mass index (BMI) >30 across European states.2 Age is important: by age 65-70, as many as 40% of all people in the UK reach a BMI >30, and 80% have a BMI >25.3 Many with BMI >30 will experience secondary medical consequences, although overall life expectancies of populations have increased steadily despite obesity and the disabilities it brings. Many factors have been associated with weight gain, difficulty achieving and maintaining weight loss, and secondary medical consequences of obesity. Some have causal influences, many are innocent bystanders, and some have no basis in science. We focus on those related to food. The energy equation—that calories consumed=calories expended +/- calories stored (as body fat or glycogen)—is always true. Obesity develops if absorbed dietary energy (calories) from foods exceeds energy expenditure for a considerable period (box 1). Similarly, excess body fat is lost if energy intake falls below expenditure. However, numerous multilevel factors contribute to determining energy expenditure, intake, and absorption, and small mismatches with food consumption over a long period can lead to large cumulative weight changes. Box 1 ### Energy balance explained Each kg of adipose tissue contains about 7000 kcal. Thus consuming just 100 kcal a day more than energy expenditure for a year could result in a … RETURN TO TEXT