Obesity

 What we know
 Incidence
 Environmental risk factors
 HEAL - CHEM Trust materials on obesity

What we know

Obesity is an excessive accumulation of body fat (adipose tissue) caused by the consumption of more energy than is expended, which results in undesirable weight gain that impairs health. The Body Mass Index (BMI), a person’s weight (in kilograms) divided by the square of his of her height (in meters), is usually used to determine obesity. According to this weight-to-height ratio, overweight is defined as a BMI equal to or greater than 25 kg/m², but less than 30 kg/m². Obesity is defined as a BMI equal to or greater than 30 kg/m² [1]. A high body mass index is a high risk factor for a number of chronic diseases including certain types of cancer, cardiovascular disease (CVD), hypertension, type II diabetes, cardiovascular disease (CVD), gallbladder disease, and psychosocial problems [2].

Incidence

Figure 1. Overweight among school-aged children in selected European countries, 1958-2003 [3] To see the enlarged version of this picture, click here and go to page 10

According to the World Health Organization (WHO) approximately 1.6 billion adults are overweight, and at least 400 million are obese. In the European region almost 400 million adults are considered overweight, between 30% and 80% of the population, whilst 130 million considered obese. Obesity has reached epidemic proportions. In the last two decades its prevalence has tripled, and if no action is taken there will be an estimated 150 million obese adults (20% of the population) and 15 million obese children and adolescents (10% of the population) in the WHO European Region by 2010 [4].

Although obesity is primarily diet induced its causes are not entirely clear. Whilst there is a component of genetic predisposition, as with other chronic diseases changes to our environment have contributed to the obesity epidemic. A wide range of environmental factors influences individual energy intake and expenditure, including family practices, school policies and procedures, transport and urban planning policies, commercial marketing activities and policies on food supply and agriculture. One of the most significant of these is an environment that restricts or eliminates the need for physical activity.

Environmental risk factors

There is a growing recognition however, that exposure to certain environmental agents early life and in utero, could also be possible risk factors, such as in utero nutrition and cigarette smoke. Furthermore, chemicals that mimic estrogens are emerging as agents of particular concern. It is suspected that estrogens regulate the size of the fat cells (adipocytes) through finely tuned pathways that have evolved to respond to minuscule changes in hormone levels. Exposure to chemicals that mimic estrogens (xenoestrogens) during critical phases of development may therefore have the potential to alter the body’s accumulation of fat. The chemicals under scrutiny include diethylstilbestrol (DES), a synthetic compound used until the 1970s to prevent miscarriage, and bisphenol A, a constituent of food and beverage containers. Both have estrogenic properties. The ubiquitous environmental pollutants organotins are also known to stimulate adipogenesis and interfere with energy balance. [5], [6], [7]

Obesity represents a significant economic burden, consuming 2-8% of overall health care budgets, depending on estimations used, definitions of obesity and systems of health care. Moreover, additional costs are associated with people who are overweight but not obese, lost productivity or premature death [8].

As a disease that is notoriously difficult to cure, prevention is pivotal in tackling the obesity epidemic. Whilst only further research into obesogenic determinants will tell whether reductions in environmental chemicals in utero and throughout life have a significant role to play in disease reduction, it is evident that obesity is one of a growing number of diseases linked to recent environmental changes. For many of these, only a multisector and multifactor approach based on scientific evidence of disease causation will succeed in reducing disease burden.