Appetite disturbance and the problems of overweight.

During the past 50 years, obesity has increasingly become a problem in Western societies. If low energy output by these individuals (i.e. lack of exercise) cannot be held totally accountable for this problem, then their energy input (i.e. appetite) must play a significant role. There are many elements that give rise to appetite disturbances and their effects on weight gain, weight loss or its maintenance. Previously, it was thought that emotional disturbances led to overeating and overweight; a theory that was supplanted later by the theory that physiological rather than psychological causes were to blame. Today, it is generally believed that appetite is controlled by the interaction of internal (genetic, physiological and chemical) and external (environmental and psychosocial) processes. The role of nutritional and dietary factors in controlling the expression of appetite are particularly important. Thus, appetite (hyperphagia or increased hunger) can be induced by changes in brain neurotransmitters and neuromodulators, altered liver metabolism, adjustments of the nutrient/sensory components of the diet, environmentally applied stressors, the mental and behavioural imposition of dieting and the administration of various psychotropic medications. This review focuses on the role of each of these mechanisms plays in the genesis and maintenance of appetite disturbances; the conclusion of each of these contributions is the same--control of appetite must be achieved in order to treat obesity, and to do this, control must be exerted via regulation of the food supply, cognitive methods, environmental adjustment or by pharmacological tools.