More than 50 per cent of adults in Wales are obese or overweight, a statistic that is predicted to increase to 85 per cent by 2020 unless remedial action is taken. Wales is the most overweight country within the United Kingdom where obesity has more than doubled in the last 25 years. It is predicted that on current trends, some 60 per cent of men and 50 per cent of women in Britain could be obese by 2050. This is estimated to represent a seven-fold increase in direct healthcare costs associated with excess weight, with wider costs to society reaching £45 billion a year. Obesity increases risks for chronic disease, including type 2 diabetes, cardiovascular disease and some cancers. The development of obesity early in life increases certain health risks significantly. Key factors influencing excessive weight gain are over-consumption of energy-dense foods, and insufficient physical activity. Scientific and other evidence shows that energy balance (or imbalance) is determined by a complex multifaceted system of determinants. We live in an ‘obesogenic environment’ in which a combination of economic, social and cultural factors make it difficult for people to maintain a healthy weight. This conference will examine Wales’s obesity epidemic and suggest policies that should be put in place to address it.