Abstract P346: Effect of Low-Fat versus Low-Carbohydrate Diet on Visceral Fat

Abstract

Introduction: A healthy low fat (HLF) and healthy low carbohydrate (HLC) diet are common strategies for weight loss that vary in their effects on adiposity and metabolism. Visceral adipose tissue (VAT) is the major contributor to metabolism deregulation, beyond subcutaneous adipose tissue (SAT). Despite strong biological evidence that a HLC diet preferentially decreases VAT relative to SAT, the difficulty in measuring adipose sub-types has impeded its use in diet trials. To address this research gap, we measured VAT and SAT in a secondary analysis of the Diet Intervention Examining The Factors Interacting with Treatment Success (DIETFITS) weight loss trial to compare the effects of HLF and HLC diets and potential effect modification by sex and insulin resistance status. Hypothesis: We hypothesized that a HLC diet is associated with greater VAT loss compared with a HLF diet. Secondly, we hypothesized that men and those with greater baseline insulin secretion assigned to HLC diet would experience greater VAT loss. Methods: DIETFITS was a single-site, parallel-group, weight loss diet trial, randomizing 609 adults with overweight and obesity to a HLC or HLF diet for 12 months. Data collection occurred at baseline, 6 months, and 12 months. Insulin resistance status was proxy measured using insulin concentration 30 minutes after a glucose challenge (INS 30). In this secondary analysis, we measured VAT and SAT in the abdominal region by reanalyzing the dual-energy x-ray absorptiometry (DXA) scans. We fit a linear mixed model to evaluate the change in VAT after 6 and 12 months on HLF and HLC, with fixed effects: time, diet, and their interaction; and a random effect for repeated observations. We built separate models for each of the secondary hypotheses, with additional fixed effects INS 30 and sex, respectively. Results: We included 449 participants with baseline DXA (60% women; mean age 40 years). From baseline to 6-months, participants assigned to a HLC diet experienced a significant 10.6 cm 2 (95% CI: 5.1, 16.1) greater decrease in mean VAT compared to those assigned to a HLF diet. The 12-month difference in diets attenuated to 5.5 cm 2 (95% CI: -0.1, 11.1). Contrary to our hypothesis, INS 30 did not modify the diet-related changes in VAT. Among men, both diets resulted in a 12-month decrease in VAT. The HLC diet was associated with a 12.1 cm 2 (95% CI: 1.6, 22.7) greater loss of VAT compared to HLF. Among women, HLF but not HLC was associated with decreased VAT, and there was no difference in VAT loss between diets 1.8 cm 2 (95% CI: -4.1, 7.6). Models controlling for SAT indicated that VAT decreased independently of SAT. Conclusion: These findings contribute to the understanding of the nuanced impacts of HLF and HLC diets on adipose sub-types and underscore the relevance of considering sex in designing effective dietary interventions targeting VAT reduction and metabolic health.