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Trends in Body Mass Index among Icelandic Adolescents and Young Adults
– Reported, January 24, 2012
Globally, the prevalence of overweight and obesity has increased among children, adolescents, and adults. Being overweight or obese is a growing public health threat because of its significant contribution to the burden of chronic diseases, including type 2 diabetes, cardiovascular disease, hypertension, and some types of cancers . Aside from human suffering, the economic consequences that accompany the morbidity and mortality associated with obesity are estimated to contribute up to 6% of the total healthcare costs in many of the European and other developed countries, with indirect costs in lost productivity adding equally as much .
In order to tailor prevention programs more effectively, a rigorous examination of the trends in adolescent onset of obesity and general trends in weight change among this age group is needed. But describing only the overweight and obese proportion of the population, or only the central part of the upper-weight distribution, provides an insufficient picture of the current situation . In doing so, the entire distribution of body mass index (BMI) may be shifted upward, or a subgroup of the population may be seen as heavier now than before, with little change in the remainder of the population . Thus, it is important to examine the shape of the whole distribution. Moreover, although prevalence rates portray the distribution of BMI, they do not provide important information about the severity of the health problem, or whether the normal, overweight, and obese are becoming heavier.
This study utilized population data from the national surveys of Icelandic adolescents, Youth in Iceland. These comprise a series of cross-sectional surveys that are conducted annually to understand trends in attitudes, values and behavior of youth along with social circumstances and background. The findings are used to enhance public understanding of youth lifestyles and to inform programs that can promote health and social well-being of Icelandic young people. The data analyzed in this study were collected in upper secondary schools at four time periods for 14- and 15-year-olds, in 1992, 1997, 2000, and 2006; and for three time periods for 16- through 20-year-olds in high-schools in 1992, 2004, and 2007. In Iceland, schooling is mandatory for youth age 6 through 15 and about 95% of upper secondary school graduates continue their education in high-schools, which are funded by the municipalities but supervised and operated by the Ministry of Education. High school typically requires about four years to complete, usually by age 19 or 20; however, the proportion of graduates that continue in high school falls to about 85% by the second year and slightly below 70% by the 4th and final year . The distribution of the student population in Iceland is consistent with the distribution of the general population, with about 63% in the capital city, Reykjavik, and surrounding areas.
Self-reported height and weight were used to calculate BMI (kg/m2). For young adults, 18 years old and above, BMI was categorized according to the World Health Organization classification as follows: underweight = 18.5 kg/m2, normal weight = 18.524.9 kg/m2, overweight = 2529.9 kg/m2, and obese = 30 kg/m2. For adolescents under 18 years of age, the International Obesity Task Force (IOTF) age- and gender-specific cut-off points for underweight, overweight and obese (based on centile curves defined to pass through the BMI of 18.5, 25 and 30 kg/m2 at age 18) were used to provide internationally comparable estimates of the prevalence among adolescents . As recommended by the IOTF , overweight was defined as the proportion of adolescents between overweight and obese, so the overweight group does not include the obese group. Because the data were collected in March, the BMI cut-off point values for half years, 14.5, 15.5, were used for upper secondary school students. Data collection among high-school students was conducted in October, thus whole-year cut-off values were used.
There were no statistically significant changes in the proportion of underweight in any age group for either gender, while a significant reduction in rates of normal weight was detected across all age groups for both genders, except from the 14- and 18-year-old girls. However, the changes in rates were slightly u-shaped for the 19-year-old boys, and 16-, 19-, and 20-year-old girls. The biggest decline in normal weight was found among 20-year-old boys, a reduction from 84.2% to 61.1%, and the most notable shift in girls was also among the 20-year-olds, a decline from 78.9% in 1992 to a 68.0% in 2004, and up to 71.2% in 2007.
Overweight and Obesity
There was a statistically significant increase in overweight during the study period among boys in all age groups and among girls in all age groups, except for the 14- and 20-year-olds. The greatest increase was found among boys in the oldest age group, an increase from 14.6% to 27.6%. Further, obesity rates increased significantly among boys in all age groups, except for 16-year-olds, and among 15 and 20-year-old girls. The biggest change in obesity rates among both genders was found in the oldest group; from 0.8% to 8.5% among the boys and from 2.6% in 1992 up to 9.2% in 2004 and down to 6.3% in 2007 among the girls.
Within Each Weight Category
There were no statistically significant trends in the underweight category apart from the 15-year-old girls, where the average BMI decreased slightly, or by 0.2 kg/m2 over the study period. In the normal-weight category, small but statistically significant increases of 0.1, 0.2, and 0.3 kg/m2, were observed among 14-, 15-, and 19-year-old boys, respectively, while a 0.2 kg/m2 u-shaped decrease, from 22.5 down to 22.1 and up to 22.3 kg/m2 in 2007, was observed among the 20-year-old boys. Similarly, among girls, small but statistically significant increases of 0.4, 0.2, and 0.2 kg/m2 were found among the 17-, 18-, and 19-year-olds, respectively. In the overweight category a significant increase in average BMI were observed among 16- and 20-year-old boys and 17-year-old girls, in whom BMI increased by 0.4, 0.6, and 0.5 kg/m2, respectively. In the obese category, there was an increase in average BMI for boys in all age groups but only statistically significantly so among the 15- and 17-year-olds, where the average BMI increased by 0.9 and 2 kg/m2, respectively. In contrast, among girls in the obese category there was a slight decrease in average BMI across all age groups, but only significantly so among the 19-year-olds, by 1.8 kg/m2, with the exception of 20-year-old girls, who experienced a mean increase of 3 kg/m2.
The percentage of 14- to 20-year-old Icelandic adolescents and young adults who are overweight increased from 1992 to 2007, except among 14- and 20-year-old girls. The prevalence of obesity increased among boys in all ages, except for 16-year-olds, and among 15- and 20-year-old girls. For the adolescents, particularly among the boys, the BMI distribution has shifted upward, indicating that few Icelandic adolescents and young adults are immune to the ecological factors that appear to account for the observed increase in weight gain that is now being seen globally. Our findings highlight the seriousness of the increasing threat posed by the obesity problem in Iceland.
Credits:Sigrídur Þ. Eidsdóttir,Álfgeir L. Kristjánsson,Inga D. Sigfúsdóttir,Carol E. Garber and John P. Allegrante.
More Information at:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2898044/?tool=pubmed