According to study results published in the Journal of the American College of Cardiology, abdominal fatness in adolescence was associated with cardiometabolic dysfunction and body mass index (BMI) was found to be a beneficial tool for predicting effects of abdominal fat over time.
BMI is often criticized because it does not account for fat distribution. Researchers in this study aimed to compare BMI calculations with regional fat indexes in their associations with cardiometabolic traits in young adulthood using data from the Avon Longitudinal Study of Parents and Children population-based cohort study. Exposure to and changes in each fat index were tracked through adolescence and examined for associations with cardiometabolic outcomes. Both BMI calculations and dual-energy X-ray absorptiometry measurements for total, abdominal, arm, and leg fat indexes were completed when children in the study were age 10 and again at age 18. Measurements of cardiometabolic traits such as blood pressure, circulating insulin, high-sensitivity C-reactive protein, cholesterol, and triglycerides were collected at age 18.
In total, there were 2840 children (55.3% female) included in the analysis. At age 10, mean BMI was 17.5 ± 2.7 kg/m² and at age 18, mean BMI increased to 22.7 ± 0.4 kg/m². Repeated measures for BMI and fat indexes at age 10 and 18 were sufficiently correlated at approximately 0.7 and changes in BMI were strongly correlated with changes in each fat index (P <.0001). At age 10, a higher BMI was strongly associated with higher systolic and diastolic blood pressure, cholesterol in very-low-density lipoprotein (LDL), insulin, glucose, and C-reactive protein as well as lower cholesterol in high-density lipoprotein (HDL). These cardiometabolic trends were similar across fat mass indexes, with abdominal fat index having a higher effect size than other regional fat indexes.
At age 18, a higher BMI was more strongly associated with negative cardiometabolic traits than at age 10, with fat mass indexes following the same pattern. Abdominal fat indexes had an even larger effect size, with the highest being for traits related to very-LDL and HDL (P <.0001).
Increases in BMI and fat indexes from age 10 to age 18 were strongly associated with higher systolic and diastolic blood pressures, total cholesterol, very-LDL, LDL, insulin, glucose, and glycoprotein acetyls and C-reactive protein, as well as lower HDL. Again, gains in fat indexes followed the same pattern as gains in BMI, with changes in abdominal fat indexes showing the most association. The effect size for increases in abdominal fat index was largest for insulin (standard difference, 0.51; 95% CI, -0.09 to 1.10, P =.10).
This study has potential for residual confounding and reverse causation bias due to the observational nature of the data, possible measurement error of fat indexes, and lack of generality due to a predominantly white study population (only 3.7% of children were of nonwhite ethnicities).
The researchers concluded both BMI and dual-energy X-ray absorptiometry fat indexes show similar association to cardiometabolic traits. “Altogether, the results support abdominal fatness as a primary driver of cardiometabolic dysfunction and BMI as a useful tool for detecting its effects,” wrote the investigators.
Bell JA, Carslake D, O’Keeffe LM, et al. Associations of body mass and fat indexes with cardiometabolic traits. J Am Coll Cardiol. 2018;72(24):3142-3154.