Abstract P083: is Change in Ectopic Fat Following A Weight Loss Intervention Associated with Change in Vascular Stiffness in Young Men and Women?

Background: Ectopic fat may be a better indicator of CVD risk than conventional measures of obesity such as BMI. Data are lacking in how changes in ectopic fat relate to changes in arterial stiffness, and whether there are differences by sex. Our objectives were to determine: (1) how ectopic fat changes after a behavioral weight loss intervention and whether changes differ by sex; and (2) if the changes in ectopic fat are associated with changes in arterial stiffness independently of BMI change. Methods: Longitudinal analyses were conducted on 203 participants with complete ectopic fat and vascular stiffness data in the Slow Adverse Vascular Effects study, a randomized trial of a behavioral weight loss intervention in 349 men and women aged 20-45 years and BMI 25-40 kg/m 2 . CT scans measured total abdominal adipose tissue (TAAT), visceral AT (VAT), total thigh AT (TTAT), and intramuscular thigh AT(IMAT). Carotid-femoral (cf) and brachial-ankle (ba) pulse-wave velocity (PWV) were measures of central and mixed central/peripheral arterial stiffness, respectively. T-tests evaluated how ectopic fat and PWV measures differed between men and women at and between baseline and 12-months. Sex-stratified linear regression analyses evaluated associations between changes in regional adiposity and arterial stiffness from baseline to 12 months. Results: Mean age of participants at baseline was 38.2 ± 5.9 years; mean BMI was 32.2 ± 3.9 kg/m 2 ; 150 (73.9%) were women; and 166 (81.8%) were white. Men were significantly (all p<0.05) different from women at baseline with more VAT (159.1 vs. 100.0 cm 2 ), less TTAT (96.1 vs. 147.8 cm 2 ), higher BMI (33.5 vs. 31.8 kg/m 2 ), higher baPWV (1257.3 vs. 1193.5 cm/s), and higher cfPWV (968.6 vs. 850.9 cm/s). At 12 months, men lost significantly more VAT (-29.2 vs. -13.7 cm 2 ) and had a greater decrease in cfPWV (-103.2 vs. -24.7 cm/s) compared to women (both p<0.05). After adjusting for age, baseline PWV, and change in SBP, decreases in TAAT and TTAT were significantly associated with improved vascular stiffness as measured by baPWV among men, and a decrease in VAT was significantly associated with improved cfPWV among women (all p<0.05). These relationships lost significance after adjusting for change in BMI. Change in BMI was itself not a significant predictor for the change in the arterial stiffness measures in either men or women in final models. Conclusions: We found several novel associations between changes in ectopic fat and PWV in young adults in a weight loss intervention; these associations differed by sex and dissipated after controlling for change in BMI. Change in BMI itself was not a significant predictor of change in either arterial stiffness measure in men or women. Further research with a larger sample and more diverse population may be warranted to better understand these associations.