Eating habits and appetite control: a psychobiological perspective.

An individual's eating behaviour is shaped by factors ranging from economic conditions and cultural practices to biological influences. The physiological system controlling appetite appears to be adapted to solving the problem of an unevenness of food supply across time, and is fairly permissive in its response to undereating and overeating. Consequently, when food is abundant, the diet is energy dense and energy expenditure is low, there is a strong tendency to become obese (i.e. obesity is better viewed as due to a 'toxic' environment than to faulty physiological control of appetite). Under such conditions the most common method of avoiding obesity is through the cognitive control of eating. However, dietary restraint and dieting are demanding tasks, and are associated with psychological costs, including significant impairment of cognitive performance. Restraint is also prone to disinhibition, with the result that it can sometimes undermine eating control, even leading to the development of highly disordered eating patterns. In part, these difficulties are due to the self-perpetuating nature of dietary habits: for example, hunger tends to be diminished during strict unbroken dieting, but increased in individuals having a highly variable eating pattern (such as occurs when eating is frequently disinhibited). These features of appetite control provide both barriers and opportunities for changing behaviour. Accordingly, there is a need for future research to focus on the psycho-social factors and the dieting practices predicting successful eating and weight control, with the objective of identifying the actual cognitive and behavioural strategies used by the many dieters and restrained eaters who are able to achieve weight loss and maintain long-term weight stability.