Changes in Diet Quality During a 12-Week Behavioral Weight Loss Intervention in Middle-Aged and Older Adults with Overweight and Obesity

Abstract

Behavioral weight loss interventions typically emphasize energy restriction and weight change, yet the impact of these interventions on overall diet quality remains underexplored – particularly in older adults. This study examined changes in diet quality during a 12-week behavioral weight loss intervention in middle-aged and older adults with overweight and obesity. This was a sub-analysis of an ongoing randomized controlled trial exploring water intake and weight control (ClinicalTrials.gov: NCT05843318) in adults aged 50 years and older. Participants were randomized to one of three groups: premeal water consumption, daily water intake, or a control group tracking fruit and vegetable intake. All groups received SCT-based behavioral counseling and a hypocaloric diet prescription. Diet quality was assessed using the Healthy Eating Index-2015, derived from three 24-hour dietary recalls at baseline and week 12. Mean HEI-2015 total scores improved significantly from 56.15 to 62.86 (p<0.0001) for the pooled sample. A significant time effect was observed across groups (p=0.0002), with no group x time interaction. Five HEI components demonstrated significant time effects: total fruits, whole fruits, whole grains, refined grains, and added sugars. No significant main group or group x time interactions were detected for any of the 13 HEI-2015 components. Reported dietary intakes of calcium, vitamin D, and vitamin B12 did not change significantly in the pooled sample, though calcium and vitamin D intakes remained well below recommended levels at both timepoints. These findings suggest that participation in a behavioral weight loss intervention can improve overall diet quality in older adults, but targeted strategies may be needed to address micronutrient inadequacies during caloric restriction.