Nutrition/Obesity
The per-protocol effect of adherence to the low-fat dietary pattern intervention on visceral adipose tissue levels in the Women’s Health Initiative Dietary Modification Trial Anais Elena Fernandez Calzavara* Anais Elena Fernandez Calzavara Jiarui Li Matthew J. Landry Jennifer W. Bea Marian L. Neuhouser Matthew Allison Thomas E. Rohan Lesley F. Tinker Linda G. Snetselaar Jean Wactawski-Wende JoAnn Manson Andrew O. Odegaard
Objective: Strong evidence supports that higher levels of abdominal visceral adipose tissue (VAT) drive obesity-related chronic disease risk. Yet, there is little evidence of the impact of specific dietary interventions, and in particular, decreasing dietary fat levels, on VAT. We estimated the per-protocol effects of adherence to the low-fat dietary intervention among postmenopausal women in the Women’s Health Initiative (WHI) Dietary Modification (DM) trial on 1-year changes in VAT levels.
Methods: The DM trial was designed to reduce total fat intake to 20% of total energy, and increase both vegetable/fruit intake to ≥5 and grain intake to ≥6 servings/day. We analyzed equation-derived estimates of VAT in participants in the DM intervention group who had baseline and year 1 whole-body dual-energy X-ray absorptiometry scans for body composition (n=1043). Adherence during this year was assessed via the year 1 food-frequency questionnaire. We used the parametric g-formula to estimate the per-protocol effect of adherence to varying levels of dietary fat intake (% of total energy), while meeting the fruit/vegetable and grain intake aspects of the intervention on 1-year VAT changes, adjusting for pre and post-randomization predictors of protocol deviation and loss to follow-up.
Results: On average, participants randomized to the DM intervention arm had a reduction of 10.3 cm2 (95% CI, -12.3, -9.0) of VAT at year 1. When classifying participants according to adherence levels of dietary fat intake during the intervention (% of total energy: > 35, ≤35, ≤30, ≤25, ≤20%), there was a respective stepwise decrease in VAT (Table), with the greatest effect aligning with adherence to the targeted intervention of ≤20%: -17.5 (95% CI, -21.7, -13.3).
Conclusions: Among postmenopausal women in the WHI DM trial, greater levels of adherence to the low-fat dietary pattern intervention corresponded to greater decreases in VAT.
