Pre-meal Planning and Expected Satiety

Obesity is considered to be caused by an imbalance between energy expenditure and energy intake. A major determinant of our daily energy intake is the size of the meals that we consume. It has been suggested that decisions about portion sizes are often made in advance, before a meal begins. This pre-meal planning is considered to especially depend on the estimated 'expected satiety' and 'expected satiation' of different foods. Further, also factors like weight concern and palatability of the food might have their influence on meal size selection. In general, it is not clear how these factors are integrated during pre-meal planning and which brain networks are involved in these decisions/this process. Thus, the investigators plan to study pre-meal planning in healthy, normal-weight and overweight/obese individuals with functional magnetic resonance imaging under different cognitive instructions including pleasure, expected satiety and self-control in terms of health consequences. The investigators will explore the neural networks involved in pre-meal planning and expect them to be modulated by the before mentioned factors. Further, the investigators plan to explore gender differences and expect that female subjects will select smaller portion sizes especially in the self-control condition as they are often more concerned about their weight/health. Finally, the investigators will explore differences between lean and overweight subjects to elucidate factors that might lead to increased meal sizes in overweight subjects.