Aetiology of obesity in adults

Biology determines the intensity of an individual's drive to eat and the strength of inhibition of the processes of satiation and satiety. These processes are interpreted in relation to the existence of an obesogenic environment that encourages over consumption. The majority of obesity has a complex multifactorial/polygenic aetiology. This chapter focuses on the physiology of obesity and the key peripheral and central signals involved in the regulation of body weight. It presents the evidence for cross-sectional and longitudinal associations between physical activity, physical fitness and sedentary behaviour with overweight and obesity in adults. The chapter then discusses the relationships between current physical activity guidelines and weight gain prevention. The potential effect of obesogenic medications is considered when evaluating individuals presenting for weight management. Effective advice and support to avoid or minimise weight gain would be the optimal approach in patients receiving treatment with obesogenic medications.