Intelligence test score, education level and obesity - Obesity

Nutrition Research Newsletter, Nov, 2003 by Jytte Halkjer

Several studies have examined the potential associations between various social factors, such as school performance, educational attainment, occupation, and income and BMI or weight changes. The results have been inconsistent. However, cross-sectional studies conducted on Danish draftees showed a clear inverse association between BMI above the median BMI and both intelligence test score and educational level. The same tendencies have also been seen in a Chinese study in children. These cross-sectional observations raise the obvious question of whether cognitive ability and educational level are determinants or consequences of changes in body weight and development of obesity. Therefore, some Danish researchers investigated intelligence test scores and educational levels in young adult men in relation to their subsequent changes in weight and risk of development and persistence of obesity.

Subjects were selected among men appearing at Danish draft boards. The men were divided into two groups: A group with juvenile-onset obesity, including all men with a BMI of greater than 31 kg/[m.sup.2]; and a non-obese group randomly selected as a 1% sample of the study population. The obese group and 50% of the non-obese group were invited to participate in follow-up studies between 1982 and 1984 and between 1992 and 1994. Among 907 men with juvenile-onset obesity and 883 non-obese men, age, region of examination, intelligence test score via the Borge Priens Prove 1953 test, education and BMI from baseline to first follow-up, were analyzed.

Within both groups, BMI significantly increased from baseline to both the first and second follow-ups. Education and intelligence, analyzed separately, were inversely related to BMI changes in both groups. A greater increase in BMI at the first follow-up occurred in the lowest intelligence test-score quintiles and in the group of less educated men in the non-obese control group. When adjusted for education, the association between intelligence score and BMI changes and the development of obesity vanished, whereas the inverse relationship for education persisted only for BMI changes. Intelligence score was not associated with the persistence of obesity in the obese group, whereas inverse relationships were found for education. The highest educated group had less than half the odds of remaining obese compared with the lowest-educated group.

Both intelligence test score and education level had an inverse effect on the subsequent BMI changes and risk of developing obesity. Educational attainment showed a strong inverse relationship with the persistence of obesity in the juvenile-onset obesity group, whereas the intelligence score had no effect. The authors speculate about several reasons for their findings. High ability in intelligence testing and educational attainment may be related to stronger expectations of a slim physical appearance and, therefore, a higher motivation for weight regulation or loss. Through their high cognitive skills, the well-educated might also have a better ability to receive and implement general-health guidelines into their everyday lifestyle, compared with less-educated groups. However, better understanding of this interaction may allow improved targeting and, thereby, more effective prevention and treatment of obesity.

Jytte Halkjer, Claus Hoist, and Thorkild I.A. Sorensen, Intelligence Test Score and Educational Level in Relation to BMI Changes and Obesity, Obesity Research 11(10): 1238-1245 (October 2003) [Address correspondence to: T.I.A. Sorensen, Institute of Preventive Medicine, Kommunehospitalet opg. 23a, DK-1399 Copenhagen K, Denmark. E-mail: tias@ipm.hosp.dk]