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

In the few weight loss studies assessing diet quality, improvements have been minimal and recommended calculation methods have not been used. This secondary analysis of a parallel group randomised trial (regsitered: https://clinicaltrials.gov/ct2/show/NCT03367936) assessed whether self-monitoring with feedback (SM + FB) v. self-monitoring alone (SM) improved diet quality. Adults with overweight/obesity (randomised: SM n 251, SM + FB n 251; analysed SM n 170, SM + FB n 186) self-monitored diet, physical activity and weight. Real-time, personalised feedback, delivered via a study-specific app up to three 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 August 2018 to March 2021 and analysed spring 2022. The sample was mostly female (78.9 %) and white (85.4 %). At baseline, HEI-2015 total scores and bootstrapped 95 % CI 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 diet quality change. Clinically meaningful weight loss was related to diet quality improvement. Feedback may need to incorporate more targeted nutritional content.