Health care systems around the globe are beginning to recognise the risk that obesity
poses to human health and many programmes are now being put into place in an
effort to reduce the burden of obesity and its related diseases. Current definitions of
obesity are based on the ratio of bodyweight (in kg) and height squared (in m2) and
expressed as body mass index (BMI) with a normal BMI defined as 20–24.9, moderate
overweight between 25–29.9 and obesity as 30. In 2000, the World Health
74 Armitage · Poston · Taylor
Organisation released the following statement: ‘Obesity is a chronic disease, prevalent
in both developed and developing countries, and affecting children as well as adults.
Indeed it is now so common that it is replacing the more traditional public health
concerns, including under-nutrition and infectious disease as one of the most significant
contributors to ill health’ [1]. At the turn of the millennium and the time of publication
of the WHO report, the incidence of obesity in the United States was 30.5%
(compared with 22.9% in 1994) and 64.5% of the population were overweight (compared
with 55.9% in 1994) [2]. More recent statistics suggest that the incidence of
obesity and overweight is rising, not falling, in spite of the apparent efforts of governments
and health care agencies. This shift in body mass has occurred over the past
one to two generations and as such it is unlikely that genetic drift is the cause of the
current obesity epidemic. Rather, a change in lifestyle, compounded by epigenetic or
developmental programming of an obese phenotype are the likely causative factors.
Obesity statistics from the United States are most often quoted, perhaps because
they give the greatest impact; however, scientific studies conducted in other nations
emphasise the fact that obesity is a worldwide problem. A study of cause of death in
South Korea illustrates this fact. In 1938, cardiovascular disease accounted for
approximately 1% of deaths in South Korea whilst infectious diseases were the cause
of approximately 23% of deaths. By 1993, this trend had reversed; approximately 30%
of deaths were attributable to cardiovascular disease whereas only 3% of deaths were
caused by infection. Certainly such statistics are affected both by the vast improvements
in anti-microbial medication and sanitation in that 60-year period; however,
the fact remains that obesity-related illness is the next public health hurdle.
Obesity may not, in itself, be a great risk to human health. Indeed, there are some
individuals who are overweight or obese but do not show any other signs of disease or
ill health. However, for the vast majority, increased body fat is associated with a range
of other, more serious conditions. These include increased blood pressure, insulin
resistance and diabetes mellitus, atherogenic plasma lipid profiles, and increased levels
of vascular inflammatory markers. Collectively, this spectrum of conditions is
termed the ‘metabolic syndrome’ and clinical diagnosis is based on the presence of 3
or more of the above signs. Endothelial dysfunction and leptin resistance are also
likely to contribute to the metabolic syndrome [3].
The rise of obesity is certainly due to the increased availability of food, and the
preponderance of energy dense (high fat and simple carbohydrate) foods that are regularly
consumed in developing and developed societies. Moreover, the industrial era
has produced all manner of labour saving devices that has ultimately seen a reduction
in the physical activity quotient over time [4]. However, despite the obvious importance
of food intake and energy expenditure during adulthood, there is now evidence
that adult lifestyle may not be the only factor at play in determining obesity [5]. The
environment encountered during the in utero and early postnatal periods may also
act to ‘programme’ an individual to have a greater risk of developing obesity and the
metabolic syndrome.
