Norges teknisk-naturvitenskapelige universitet, Institutt for samfunnsmedisin
Abstract
Background Body shape and size have through centuries mediated important messages of both social status and health. A well-nourished body has been associated with status and wealth, while underweight has indicated poverty and poor health. The increasing welfare after the Second World War seemed to change the language of the body shape and size. The lean body became the ideal, and overweight and obesity became associated with lower social status and unhealthy lifestyle. Eating problems developed especially among adolescents in the western world in the same time-frame with substantial changes in diet and physical activity resulting in increased prevalence of overweight and obesity. Both eating problems and weight problems reduce quality of life, and may lead to several serious disorders in adulthood. To be able to prevent these health problems in adolescents it is important to follow the prevalence of eating problems as well as overweight and obesity, using repeated measures with the same methods and definitions. Little focus has been on sex differences in eating problems as this often has been treated as a female issue. There has also been little focus on sex differences in the prevalence of overweight and obesity. Aim With focus on sex differences, the aim of this study was first to assess the prevalence of eating problems in adolescents and the significance of different definitions used (Paper I). A second aim was to evaluate changes in the BMI-distribution and prevalence of overweight and obesity in the same geographical area during a period of 30 years (Paper II and III). The last aim was to evaluate the associations between weight problems (underweight, overweight and obesity) and psychological factors like anxiety, depression, self esteem, eating problems and personality, and to study the significance of these psychological factors on weight change during adolescence (Paper IV). Material and Methods Data from Young-HUNT 1 (the youth part of The Nord-Trøndelag Health Study1995-97) was used to assess the prevalence of eating problems and to study associations between weight problems and psychological factors including eating problems. Totally, 8090 adolescents (4018 boys and 4072 girls) aged 13-18 years completed the Young-HUNT questionnaire and had their height and weight measured in the clinical part of the study. To evaluate changes in the BMI-distribution and the prevalence of overweight and obesity, data from adolescents aged 14-18 years in Young-HUNT 1 (3307 boys and 3367 girls) was compared to data from 4372 boys and 4006 girls in the same age group, collected in the same geographical area by the National Health Screening Service in 1966-69. Among the participants in Young- HUNT 1, 1619 adolescents (747 boys and 872 girls) participated in Young- HUNT 2 four years later (2000-01), and had their height and weight measured. Data from Young- HUNT 1 was used to study the possible influence from psychological factors on weight change during adolescence (from Young-HUNT 1 to Young- HUNT 2). Results The prevalence of eating problems varied depending on the definitions used, with 47 % of the girls and 30% of the boys fulfilling at least one criterion for eating problem. The overlap between the different definitions was low indicating that the various definitions capture different eating features. The various definitions also gave different gender rations, but always with higher prevalence in girls compared to boys, and increasing with age in girls only. In 1995-97 17.2 % of adolescents in Nord-Trøndelag fulfilled the criteria for overweight or obesity, a 60 % increase from 1966-69 when the prevalence in the same age group was 10.7%. The extent of overweight and obesity had also increased, and the increase in both prevalence and extent was most prominent in boys. The change in the BMI-distribution during the same time period showed an increased dispersion and a two-sided change with a significant increase in the upper percentiles and a trend towards a decrease in the lowest percentiles, i.e the thinnest adolescents were thinner, while the most overweight were fatter. Mean BMI in girls did not increase in this period. Eating problems were associated with weight problems, and the two factors oral control (EAT-A) and food preoccupation (EAT-B) demonstrated an inverse association. Oral control was associated with underweight, while food preoccupation was associated with overweight and obesity. Low self-esteem was also associated with overweight and obesity. Oral control protected against unhealthy weight gain, but predicted unhealthy weight reduction. No psychological factors were found to predict healthy weight reduction. Conclusions Eating- and weight problems were common in the adolescent population, but varied with definition and in degree. Eating problems were more frequent in girls, but weight gain was more prominent in boys. Eating problems were associated with weight problems, and also with weight change. It is important to prevent these health problems in adolescents, and effective preventive strategies need to focus on sex differences and to bear in mind the associations between psychological factors and weight problems