Diet, nutrition and the prevention of excess weight gain and obesity This review summarizes the evidence on the factors contributing to obesity and strategies to prevent it. Key protective factors include regular physical activity, high dietary fibre intake, supportive home and school environments, and breastfeeding. Risk factors include sedentary lifestyles, high intake of energy-dense, micronutrient-poor foods, heavy marketing of such foods, sugar-sweetened drinks, and adverse social and economic conditions. Strategies to reduce obesity include influencing the food supply, reducing marketing of energy-dense foods, promoting physical activity through urban environments, and improving health services for breastfeeding and managing overweight individuals. Obesity is a major health threat in both low- and high-income countries. The review highlights the need for comprehensive programs to address the epidemic. The prevalence of obesity is increasing globally, with significant variations between and within countries. In the US, obesity rates have risen from 12–20% in 1978 to 16% in 1995. In Asia, obesity rates have rapidly increased, with Chinese men's BMI over 25 kg/m² tripling from 4% to 15% in 8 years. Pacific populations have some of the highest obesity rates. The nutrition transition, characterized by westernization, urbanization, and mechanization, has led to diets high in fat, energy-dense foods, and sedentary lifestyles. This has contributed to the rapid increase in obesity, often coexisting with chronic undernutrition in low-income countries. Obesity is associated with increased mortality, type 2 diabetes, cardiovascular disease, and other health issues. The economic burden of obesity is substantial, with direct healthcare costs in the US accounting for 5.7% of total healthcare expenditure in 1995. Potential aetiological factors include dietary patterns, such as snacking, restrained eating, and binge eating, as well as environmental factors like eating out and the availability of energy-dense foods. Breastfeeding is suggested as a protective factor against childhood obesity. The review also discusses the role of percent fat, carbohydrate, and energy density in diet, noting that high-fat diets may promote weight gain through energy density and palatability. However, the evidence is mixed, and more research is needed to clarify the effects of different dietary components on obesity. The review concludes that a comprehensive approach is needed to address the obesity epidemic, including public health strategies, population nutrition goals, and further research into effective interventions.Diet, nutrition and the prevention of excess weight gain and obesity This review summarizes the evidence on the factors contributing to obesity and strategies to prevent it. Key protective factors include regular physical activity, high dietary fibre intake, supportive home and school environments, and breastfeeding. Risk factors include sedentary lifestyles, high intake of energy-dense, micronutrient-poor foods, heavy marketing of such foods, sugar-sweetened drinks, and adverse social and economic conditions. Strategies to reduce obesity include influencing the food supply, reducing marketing of energy-dense foods, promoting physical activity through urban environments, and improving health services for breastfeeding and managing overweight individuals. Obesity is a major health threat in both low- and high-income countries. The review highlights the need for comprehensive programs to address the epidemic. The prevalence of obesity is increasing globally, with significant variations between and within countries. In the US, obesity rates have risen from 12–20% in 1978 to 16% in 1995. In Asia, obesity rates have rapidly increased, with Chinese men's BMI over 25 kg/m² tripling from 4% to 15% in 8 years. Pacific populations have some of the highest obesity rates. The nutrition transition, characterized by westernization, urbanization, and mechanization, has led to diets high in fat, energy-dense foods, and sedentary lifestyles. This has contributed to the rapid increase in obesity, often coexisting with chronic undernutrition in low-income countries. Obesity is associated with increased mortality, type 2 diabetes, cardiovascular disease, and other health issues. The economic burden of obesity is substantial, with direct healthcare costs in the US accounting for 5.7% of total healthcare expenditure in 1995. Potential aetiological factors include dietary patterns, such as snacking, restrained eating, and binge eating, as well as environmental factors like eating out and the availability of energy-dense foods. Breastfeeding is suggested as a protective factor against childhood obesity. The review also discusses the role of percent fat, carbohydrate, and energy density in diet, noting that high-fat diets may promote weight gain through energy density and palatability. However, the evidence is mixed, and more research is needed to clarify the effects of different dietary components on obesity. The review concludes that a comprehensive approach is needed to address the obesity epidemic, including public health strategies, population nutrition goals, and further research into effective interventions.