ANALYSIS - Obesity is one of today's leading human health issues but it is a complex issue, often over-simplified in the media, writes senior editor, Jackie Linden. Food intake and calorie imbalance aren't new phenomenons, rather they have a wave-like history.
At a meeting held at the University of Nottingham in the UK last week, Professor Mike Gibney of University College Dublin helped sort the facts from fiction.
Speaking to a packed auditorium, Professor Gibney put obesity in the human population into its correct perspective as a modern human health issue.
Before one can begin to define a putative role for any food category in the current epidemic of obesity, a number of key issues need to be addressed in the context of any long-term approach to this public health issue, he explained.
Professor Gibney began his presentation by saying that the rate of increase in the levels of obesity is often portrayed as being of recent origin and linear in form. He showed, however, that ancient civilisations worshiped obese female images representing fertility. In fact, obesity over documented history has followed wave–like growth with periods of strong growth followed by periods of stability.
Physical activity at moderate levels can abate most, if not all, of the risk factors arising from obesity such as diabetes and hypertension, he said. Fit people are much healthier in terms of blood lipids and pressure as well as insulin levels than those who are unfit, regardless of body mass index.
The trends over recent decades away from physical work in developed societies and towards sedentary pursuits have reduced our energy expenditure and exacerbated issues of overweight.
There is a genetic component of obesity, said Professor Gibney, but it has been shown to be related to a number of risk alleles, rather than individual genes (with a few very rare exceptions). Very strong data show that obesity and over-weight are strongly heritable, to a degree shown also for alcoholism, schizophrenia and arthritis. Indeed, in many countries for which data are available, there is evidence that the rate of obesity has levelled off, indicating that the obesogenic environment may have met its full genetic potential.
Finally, Professor Gibney identified one issue that complicated the whole field of obesity from the point of view of food intake and that is significantly under-reporting, which puts the validity of epidemiological studies in some doubt. However, he stressed that this under-reporting is not confined to any specific food group but covers all categories of foods ingested. Under-reporting can involve the denial of over-consuming a given food, misreporting the frequency of consumption and/or misreporting portion size. It is impossible to see how these discrepancies can be corrected by any statistical modelling, he added.
Against this background, it is unlikely that any one food group can play a unique role in the development of obesity, according to Professor Gibney in his written paper. It is possible to explore the role of specific nutrients that are mainly derived from animal foods in aspects of obesity. For example, the role of vitamin D in the development in type 2 diabetes is highly controversial and has been played down by the US Institute of Medicine. Equally, calcium intake have been linked both to the development of obesity and to the issue of weight loss. There has also been some interesting work with fatty acids such as palmitoleic acid and conjugated linoleic acid.
The latest data show a leveling off in obesity rates among children and adolescents in Australia, Europe, Japan and the US. This good news must be viewed, however, in light of a continuing rise in adults in Europe and Australia, and a high but stable situation in American adults.
Professor Gibney concluded that there are no simple solutions to obesity in the human population but that long-term planning is required. While governments and the World Health Organization (WHO) are looking to 2020, he stressed the need to engage with the food industry as they are certainly laying down plans now for the end of the century.