Researchers believe obesity raises people's risk of suffering from chronic diseases, including diabetes, cardiovascular disease and certain cancers. And with the incidence of obesity increasing in Europe and the rest of the world, it is important to achieve a more accurate estimate of future obesity prevalence. This can be achieved by obtaining and using data from longitudinal studies. The problem is that insufficient longitudinal data is published in literature compared with results of cross-sectional data. New research, presented in the journal PLoS ONE, tackles this issue through the DIOGENES ('Diet, obesity and genes') project, which received more than EUR 14 million under the 'Food quality and safety' Thematic area of the EU's Sixth Framework Programme (FP6).
Researchers led by the German Institute of Human Nutrition Potsdam included subjects from five countries involved in the European Prospective Investigation into Cancer and Nutrition (EPIC) study: Denmark, Germany, Italy, the Netherlands and the United Kingdom.
'The EPIC study has been approved by each local ethics committee of all participating study centres,' the authors of the study note. From 1992 to 1998, the researchers recruited more than 146 500 participants and followed up on 69.8% of the sample from 1998 to 2005. 'We excluded subjects with missing dietary or follow-up data, women who were pregnant at baseline or follow-up, subjects who were in the top and bottom 1% energy intake/energy expenditure ratio, and those with implausible anthropometric measures,' the authors explain. 'Furthermore subjects with missing dates of recruitment were excluded; eventually 97 942 persons (41 456 men and 56 486 women) were available for the final analysis.'
During their follow-up period, the team found that obesity prevalence increased from 13% to 17%. They identified a link between increasing age and a strong rise of obesity in cross-sectional analyses — 30 and 65 years. But they found these curves differ between baseline and follow-up, especially for those aged 65 to 75 years old.
'Whereas in the initial baseline data, lower prevalences could be observed among the 65-to-75-year age group than in the younger age groups, the high level of obesity prevalence at follow-up persisted even at this old age,' the authors write. 'The positive relationship between age and obesity prevalence was also observed in most of the individual centres, although the magnitude of increase differed. The increase of obesity prevalence with rising age was especially marked in Amsterdam-Maastricht, Florence and Potsdam in both sexes, as well as in Doetinchem and the Danish centres among females.'
According to the researchers, a linear projection of the obesity rise during follow-up to the year 2015 would lead them to expect obesity prevalence of around 30% in the subjects aged 40 to 65 years at baseline in this cohort, which is similar to the rates currently found in the United States.
'The levelling off model predicted also considerable obesity prevalence in 2015, but with a much lower value compared to the linear model, with a mean estimate of about 20% among persons aged 40 to 65 years initially of the Diogenes cohort,' they write.
They point out that overall, the non-linear approach of prediction is seemingly more realistic, 'whereas the linear scenario is more likely to result in an overestimation of future obesity prevalences'. They believe that age-associated diseases will trigger a levelling off in future weight gain and thus, obesity trends might slow down.