Leisure-time physical activity habits and abdominal adiposity in young adulthood : twin cohort and co-twin control studies

Abstract

Twin study designs were utilized to investigate how and what types of leisure- time physical activity (LTPA) are associated with abdominal adiposity in young adulthood taking into consideration diet and other selected health factors. The data of two studies were used: the longitudinal FinnTwin16 cohort and the clinical FITFATWIN study. In FinnTwin16, questionnaire data together with self- measured waist circumference (WC) of 3 383 (1 578 men) cohort members at mean ages 24.5 y and 34 y were used to study LTPA level and waist gain. Cross- sectional data of 4 027 (1 874 men) cohort members at mean age 34 y was used to study LTPA modes and WC. In FITFATTWIN study, ten monozygotic (MZ) male twin pairs discordant for LTPA (mean age 34 y) participated in series of comprehensive health measurements including MRI of abdomen. In the longitudinal study, an increase in LTPA or staying active during the follow-up decade was associated with less waist gain, but any decrease in activity level, regardless of baseline activity, led to a waist gain resembling that of persistently inactive subjects. The difference in waist gain between the MZ twins whose activity decreased and their co-twins whose activity increased was significant. In the cross-sectional study, the number of sport disciplines engaged in was inversely associated with WC. This result persisted after adjustment for LTPA volume and diet quality. In men, all three activity types (aerobic, power and mixed) were individually associated with smaller WC, while in women this association was found only for mixed and power activities. The FITFATTWIN study revealed that in the absence of an overall difference in BMI (~3%), the less active male co-twins tended to have more body fat (~21%), and had an average 31 % more intra-abdominal adipose tissue (IAAT), and 41% more intraperitoneal adipose tissue than their genetically identical but more active brothers. IAAT was associated with the markers of glucose homeostasis. Diet did not differ between co-twins. The findings of this dissertation underline the importance of adopting and maintaining an adequate level of LTPA from young adulthood onward, independently of genes, in seeking to minimize abdominal fat accumulation and the possible development of related metabolic complications.