New thoughts on managing obesity
Authors: P G Kopelman
Journal: Gut (2004)

OBESITY AS A PUBLIC HEALTH PROBLEMObesity is defined as a body mass index (BMI) of 30 kg/m 2 or more, where a person's BMI is defined as their weight in kg divided by the square of their height in metres.Overweight is defined as a BMI between 25 and 29.9 kg/m 2 .In 1980, 6% of men and 8% of women in the UK were obese.In 2000, the respective figures had increased to 21% and 21.4%.Approximately 55% of the adult population is overweight or obese. 1 Obesity causes or exacerbates a large number of health problems, both independently and in association with other diseases. 2In particular, it is associated with the development of type 2 diabetes mellitus, coronary heart disease, an increased incidence of certain forms of cancer, obstructive sleep apnoea, and osteoarthritis of large and small joints.The Build and Blood Pressure Study has shown that the adverse effects of excess weight tend to be delayed, sometimes for 10 years or longer. 3Life insurance data and epidemiological studies confirm that increasing degrees of overweight and obesity are important predictors of decreased longevity.In the Framingham Heart Study, the risk of death within 26 years increased by 1% for each extra pound (0.45 kg) increase in weight between the ages of 30 years and 42 years, and by 2% between the ages of 50 years and 62 years. 4Despite this evidence, many clinicians continue to consider obesity to be a self-inflicted condition of little medical significance.Increasing body fatness is accompanied by profound changes in physiological function.These changes are, to a certain extent, dependent on the regional distribution of adipose tissue.Generalised obesity results in alterations in total blood volume and cardiac function while the distribution of fat around the thoracic cage and abdomen restricts respiratory excursion and alters respiratory function.The intra-abdominal visceral deposition of adipose tissue, which characterises upper body obesity, is a major contributor to the development of hypertension, elevated plasma insulin concentrations and insulin resistance, hyperglycaemia, and hyperlipidaemia.In 1988, Reaven coined the term syndrome X to refer to the clustering of (abdominal) obesity, hypertriglyceridaemia, reduced levels of high density lipoprotein (HDL) cholesterol, hyperinsulinaemia, glucose intolerance, and hypertension. 5To this basic cluster of abnormalities have been added further metabolic alterations that include increased atherogenic small, dense low density lipoprotein particles, elevated apo B concentrations, and raised plasminogen activator inhibitor 1.The syndrome is now referred to as the metabolic syndrome or insulin resistance syndrome, the latter identifying the likely pivotal biochemical abnormality.Reaven estimated that the prevalence of insulin resistance within the sedentary adult population of North America is approximately 25% and closely linked to central (visceral) obesity.Several cohort studies have confirmed that upper body (visceral) obesity is associated with greater cardiovascular morbidity and mortality than obesity itself.Obesity is not a single disorder but a heterogeneous group of conditions with multiple causes.Although genetic differences are of undoubted importance, the marked rise in the prevalence of obesity during the past 30 years is best explained by behavioural and environmental changes that have resulted from technological advances.An effective programme for the management of overweight and obesity must take account of these changes and address the aetiological factors contributing to weight gain. AETIOLOGY OF HUMAN OBESITY cAt its simplest level the ''cause'' of obesity is already known.By definition it results from an imbalance between energy intake and energy expenditure.In any individual excessive caloric intake or low energy expenditure, or both, may explain the development of obesity.Multiple studies over several decades have attempted to clarify the relative roles of energy intake and energy expenditure in human obesity.The lack of consensus, despite intensive efforts, reflects a 1044