Obesity can be managed so long as changes are made to people's lifestyles, writes Giles Warrington.
OBESITY IS A chronic disease of excess body fat that results from an energy imbalance caused by energy intake exceeding energy expenditure. The simplest way to determine body fat levels is to use the body mass index (BMI), which estimates body composition according to a person's height and weight.
Overweight adults are classified as having a BMI of between 25-29.9 whereas obese individuals would have a BMI of greater than 30, while morbidly obese is defined as having a BMI greater than 40.
Over the past two decades the rapidly rising levels of obesity in the developed and developing world have become an emerging health problem with the prevalence in many countries, including Ireland, reaching epidemic levels.
Obesity is a risk factor for the development of cardiovascular disease, cancer, type 2 diabetes and hypertension. Furthermore, evidence suggests that death from all causes is higher in those who are overweight and obese.
The risk associated with obesity is of a particular concern in an Irish context, given our high mortality rate from cardiovascular disease, where it is estimated that about 50 per cent of adults over 18 are overweight - with one in five being obese.
In the United States alone it is estimated that $100 billion is spent annually on treating obesity-related conditions, with the direct cost of obesity being in the region of 5-10 per cent of total healthcare expenditure.
Of growing concern is the worldwide trend for increased childhood obesity, the growth of which has been particularly dramatic over the past decade. In Ireland, the North South Survey of 19,617 school-aged children published in 2007 revealed that almost one in four boys and over one in four girls were either overweight or obese.
Compared with 60 years ago, the average 14-year-old boy is typically 16 per cent taller but 65 per cent heavier. This disproportionate increase in body weight is similar for girls with the typical 14 year old being 11 per cent taller and 49 per cent heavier than her post-war counterpart.
Over this same time period average life expectancy has increased noticeably. However, despite advances in medicine and healthcare, due to the health impact of obesity, for the first time in modern civilisation children born in the 21st century may have a shorter life expectancy than their parents.
The rapidly rising overweight and obesity rates in Ireland are indicative of a large proportion of the population consistently expending fewer calories than they consume, leading to a positive energy balance and weight gain. In school-aged children the lack of adequate physical education provision and a deficiency in school-based emphasis on life-long participation in physical activity is but one factor explaining the decline in exercise patterns of Irish youths.
For many overweight and obese adults, poor dietary habits and inactive lifestyles are often laid down in childhood.
Clearly, trying to explain the mechanisms underlying the current obesity explosion is complex and, in many cases, the causes are multi-factorial. To date, there is only limited reliable data available investigating the relative contributions made by energy intake and expenditure to the rising obesity epidemic, though both, along with genetic, lifestyle, cultural and socio-economic factors, are thought to be important determinants.
To assume our bulging waistlines are due merely to a matter of gluttony would be far too simplistic. There is growing evidence to suggest that societal changes and, in particular, modern inactive lifestyles are at least as important as diet and probably the primary determinant of obesity.
One study investigating 12,000 Finnish adults over a five-year period suggested that low levels of physical activity were identified as a more important risk factor for the development of excessive weight gain and obesity than any features of dietary habits.
Furthermore, data reported for the UK in the 1990s would suggest that the increased prevalence of obesity seemed to be unrelated to changes in total energy intake. However, in the latter study, the analysis used general population-based estimates of energy intake and, therefore, its significance should not be overemphasised.
Based on current evidence, it is clear that any public health strategy targeting obesity should have a dual focus in reducing excessive energy intake (and in particular the fat content) but perhaps more importantly, redress the growing pattern of inactivity in daily living.
A variety of initiatives combining diet and exercise will lead to weight loss, however if these interventions cease the weight will be regained and possibly increased further. In essence then, overweight and obesity are not curable but may be managed so long as permanent changes are made to lifestyle.
The report of the Obesity Taskforce published in 2005 was a step in the right direction, but its 99 recommendations remain largely inspirational. Such a strategy needs to be implemented as a matter of priority if there is any chance of reversing the current trend in Ireland towards increased obesity and the associated health consequences - and the subsequent burden for society as a whole.
Dr Giles Warrington is a sport and exercise physiologist and lecturer in the School of Health and Human Performance at Dublin City University (DCU)