What are the health consequences of obesity and overweight?

The health consequences of obesity and overweight are many and varied, ranging from an increased risk of premature death to several non-fatal but debilitating and psychological complaints that can have an adverse effect on quality of life [18].

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
Alteration of the 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 [19].

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 [20]. 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 [21].

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 [22]. 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" [23].

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 [24].

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 [25].

What is the economic cost of obesity and overweight? International studies on the economic costs of obesity have shown that they account for between 2% and 7% of total health care costs, the level depending on the way the analysis is undertaken [15].

In France, for example, the direct cost of obesity-related diseases (including the costs of personal health care, hospital care, physician services and drugs for diseases with a well established relationship with obesity) amounted to about 2% of total health care expenditure [26].

In The Netherlands, the proportion of the country's total general practitioner expenditure attributable to obesity and overweight is around 3–4% [27]. In England, the estimated annual financial cost of obesity is £0.5 billion in treatment costs to the National Health Service and the impact on the economy is estimated to be around £2 billion. The estimated human cost of obesity is 18 million sick days a year; 30 000 deaths a year, resulting in 40 000 lost years of working life and a shortened lifespan of nine years on average [28].

What groups are responsible for promoting healthy lifestyles? Promoting healthy diets and increased levels of physical activity to control overweight and obesity must involve the active participation of many groups including governments, health professionals, the food industry, the media and consumers. Their shared responsibility is to help promote healthy diets that are low in fat, high in complex carbohydrates and which contain large amounts of fresh fruits and vegetables.

Greater emphasis on improved opportunities for physical activity is clearly needed, especially with increased urbanisation, the ageing of the population and the parallel increase in time devoted to sedentary pursuits.

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