The major health problems associated with obesity and overweight are:

• Type 2 diabetes
• Cardiovascular diseases and hypertension
• Respiratory diseases (sleep apnea syndrome)
• Some cancers
• Osteoarthritis
• Psychological problems
• A decrease in perceived quality of life

The degree of risk is influenced for example, by the relative amount of excess body weight, the location of the body fat, the extent of weight gain during adulthood and amount of physical activity. Most of these problems can be improved with relatively modest weight loss (10 to 15%), especially if physical activity is increased too.
 

Type 2 diabetes

Of all serious diseases, it is Type 2 diabetes (the type of diabetes which normally develops in adulthood and is associated with overweight) or non-insulin-dependent diabetes mellitus (NIDDM), which has the strongest association with obesity and overweight. Indeed, the risk of developing Type 2 diabetes rises with a BMI that is well below the cut-off point for obesity (BMI of 30). Women who are obese are more than 12 times more likely to develop Type 2 diabetes than women of healthy weight. The risk of Type 2 diabetes increases with BMI, especially in those with a family history of diabetes and decreases with weight loss.
 

Cardiovascular disease and hypertension

Cardiovascular disease (CVD) includes coronary heart disease (CHD), stroke and peripheral vascular disease. These diseases account for a large proportion (up to one third) of deaths in men and women in most industrialised countries and their incidence is increasing in developing countries.

Obesity predisposes an individual to a number of cardiovascular risk factors, including hypertension and elevated blood cholesterol. In women, obesity is the third most powerful predictor of CVD after age and blood pressure. The risk of heart attack for an obese woman is about three times that of a lean woman of the same age.

Obese individuals are more likely to have elevated blood triglycerides (blood fats), low density lipoprotein (LDL) cholesterol ("bad cholesterol") and decreased high density lipoprotein (HDL) cholesterol (“good cholesterol”). This metabolic profile is most often seen in obese people with a high accumulation of intra-abdominal fat ("apples") and has consistently been related to an increased risk of CHD. With weight loss, the levels of triglycerides can be expected to improve. A 10 kg weight loss can produce a 15% decrease in LDL cholesterol levels and an 8% increase in HDL cholesterol.

The association between hypertension (high blood pressure) and obesity is well documented and the proportion of hypertension attributable to obesity has been estimated to be 30-65% in Western populations. In fact, blood pressure increases with BMI; for every 10 kg increase in weight, blood pressure rises by 2-3mm Hg. Conversely, weight loss induces a fall in blood pressure and typically, for each 1% reduction in body weight, blood pressure falls by 1-2mm Hg.

The prevalence of hypertension in overweight individuals is nearly three times higher than in non-overweight adults and the risk in overweight individuals aged 20-44 years of hypertension is nearly six times greater than in non-overweight adults.
 

Cancer

Although the link between obesity and cancer is less well defined, several studies have found an association between overweight and the incidence of certain cancers, particularly of hormone-dependent and gastrointestinal cancers. Greater risks of breast, endometrial, ovarian and cervical cancers have been documented for obese women and there is some evidence of increased risk of prostate and rectal cancer in men. The clearest association is with cancer of the colon, for which obesity increases the risk by nearly three times in both men and women.
 

Osteoarthritis

Degenerative diseases of the weight-bearing joints, such as the knee, are very common complications of obesity and overweight. Mechanical damage to joints resulting from excess weight is generally thought to be the cause. Pain in the lower back is also more common in obese people and may be one of the major contributors to obesity-related absenteeism from work.
 

Psychological aspects

Obesity is highly stigmatised in many European countries in terms of both perceived undesirable bodily appearance and of the character defects that it is supposed to indicate. Even children as young as six perceive obese children as “lazy, dirty, stupid, ugly, liars and cheats”.

Obese people have to contend with discrimination. A study of overweight young women in the USA showed that they earn significantly less than healthy women who are not overweight or than women with other chronic health problems.

Compulsive overeating also occurs with increased frequency among obese people and many people with this eating disorder have a long history of bingeing and weight fluctuations.

References
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• Parillo, M. and G. Riccardi, Diet composition and the risk of Type 2 diabetes: epidemiilogical and clinical evidence. British Journal of Nutrition, 2004. In press.
• Hubert, H.B., et al., Obesity as an independent risk factor for cardiovascular disease: a 26-year follow-up of participants in the Framingham Heart Study. Circulation, 1983. 67: p. 968-977.
• Dattilo, A.M. and P.M. Kris-Etherton, Effects of weight reduction on blood lipids and lipoproteins: a meta analysis. American Journal of Clinical Nutrition, 1992. 56: p. 320-328.
• Seidell, J.C., et al., Overweight and chronic illness - a retrospective cohort study, with follow-up of 6-17 years, in men and women initially 20-50 years of age. Journal of Chronic Diseases, 1986. 39: p. 585-593.
• Wadden, T.A. and A.J. Stunkard, Social and psychological consequences of obesity. Annals of Internal Medecine, 1985. 103: p. 1062-1067.
• Gortmaker, S.L., et al., Social and economic consequences of overweight in adolescence and young adulthood. New England Journal of Medicine, 1993. 329: p. 1008-1012.
• Spitzer, R.L., et al., Binge eating disorder: a multisite field trial of the diagnostic criteria. International Journal of Eating Disorders, 1992. 11: p. 191-203.
• Levy, E., et al., The economic costs of obesity: the French situation. International Journal of Obesity, 1995. 19: p. 788-792.
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