Effect of an mHealth weight loss intervention on Healthy Eating Index diet quality: the SMARTER randomised controlled trial

Abstract

Few weight loss studies have assessed diet quality. In those that have, improvements have been minimal and recommended calculation methods have not been used. This secondary analysis of a parallel group randomized trial assessed whether self-monitoring with feedback (SM+FB) versus self-monitoring alone (SM) improved diet quality. Adults with overweight/obesity (Randomized: SM n=251, SM+FB n=251; Analyzed SM n=170, SM+FB n=186) self-monitored diet, physical activity, and weight via Fitbit and a digital scale. Real-time, personalized feedback, delivered via a study-specific app up to 3 times daily, was based on reported energy, fat, and added sugar intake. Healthy Eating Index 2015 (HEI-2015) scores were calculated from 24-hour recalls. Higher scores represent better diet quality. Data were collected from August 2018 to March 2021 and analyzed in spring 2022. The sample was mostly female (78.9%) and white (85.4%). At baseline, HEI-2015 total scores and bootstrapped 95% confidence intervals were similar by treatment group (SM+FB: 63.11 [60.41, 65.24]; SM: 61.02 [58.72, 62.81]) with similar minimal improvement observed at 6 months (SM+FB: 65.42 [63.30, 67.20]; SM: 63.19 [61.22, 64.97]) and 12 months (SM+FB: 63.94 [61.40, 66.29]; SM: 63.56 [60.81, 65.42]). Among those who lost ≥5% of baseline weight, HEI-2015 scores improved (baseline: 62.00 [58.94, 64.12]; 6 months: 68.02 [65.41, 71.23]; 12 months: 65.93 [63.40, 68.61]). There was no effect of the intervention on weight loss or association with diet quality change. However, clinically meaningful weight loss was related to diet quality improvement. Feedback may need to incorporate more targeted nutritional content to improve diet quality. This study is registered at: https://clinicaltrials.gov/ct2/show/NCT03367936