The current obesity epidemic is largely driven by environmental factors, including nutritional transition
towards refined and fatty foods with the growing production of energy-dense food at relatively low cost,
increased access to motor vehicles, mechanisation of work and sedentary lifestyles. These influences in
modern society are modified by individual characteristics. Ultimately, energy intake in excess of caloric
expenditure causes obesity, but why this occurs in some but not all individuals is not known. Obesity is
more prevalent in the lower socioeconomic classes but even so, there is a varying relation of socioeconomic
status with obesity between countries at different stages of development and, even in the
Western world, socioeconomic gradients with respect to obesity are both heterogeneous and in transition.
Potential mechanisms for an effect of obesity on subsequent social status have been proposed, the
most obvious being related to the stigmatisation experienced by the obese. Obesity seems to be
causally related to mood disturbances, whereas there is no conclusive evidence that the reverse is true.
When considering psychological aspects of obesity, depressive symptoms are more likely to be consequences,
rather than causes of obesity.
