The effects of physical and emotional status on adherence to a low-fat dietary pattern in the Women's Health Initiative.

Objective: To examine whether the effects of physical and emotional status on adherance to a low-fat (20% energy) dietary pattern are mediated by participation in an intervention program (attending sessions and self-monitoring).
Design: The Baron and Kenny mediator model, a series of 4 regression analyses, was used to evaluate whether: a) physical and emotional status predicted program participation, b) program participation predicted dietary adherence, c) physical and emotional status factors predicted dietary adherence, and, ultimately d) the effects of physical and emotional status on dietary adherence were mediated by program participation.
Subjects/setting: Data from 13,277 postmenopausal women randomly assigned to the low-fat intervention arm of the Women's Health Initiative Dietary Modification Trial.
Intervention: The nutrition goals for women randomly assigned to the low-fat intervention were to reduce total fat intake to 20% or less of energy from fat and to consume 5 or more fruit/vegetable servings daily and 6 or more grain servings daily.
Main Outcome Measures: Year 1 program participation (degree of attending group sessions and submitting fat scores) and adherence to the low-fat dietary pattern (percent energy from fat) as predicted by baseline physical and emotional status (eight SF-36 Health Survey subscales).
Results: Participating in the dietary intervention program reduced (mediated) the negative effect of poorer mental health on dietary adherence by 15%. Additional findings included that a 10% increase in physical functioning increased session attendance by 0.4% (P<.001) and a 10% increase in mental health predicted a decrease in percent energy from fat of 0.3% (P<.001). Program participation had a marked effect on dietary adherence: a 10% increase in session attendance predicted a 1.2% decrease in percent energy from fat (P<.001).
Applications/conclusions: Understanding and using instruments to assess the physical and emotional status of a target population will help dietetic professionals promote healthful dietary change and maintenance.