Oral Presentation Australian and New Zealand Obesity Society Annual Scientific Conference 2026

Diet intake and diet quality changes during the first 12 weeks of GLP-1 Receptor agonist therapy in Australian adults with obesity (144508)

Nicola Edwards-Kalaf 1 , Evelyn B Parr 2 , Angelique F Ralph 3 , Gennaro D'Elia 2 , Katherine Roberts-Thompson 2 , Xochitl de la Piedad Garcia 4 , Samara Legrand 5 , Tracy A McCaffrey 5 , Brooke L Devlin 1
  1. School of Human Movement and Nutrition Sciences, Faculty of Health, Medicine and Behavioural Sciences, The University of Queensland, Brisbane, QLD, Australia
  2. Centre for Human Metabolism and Performance, Mary MacKillop Institute for Health Research, Australian Catholic University, Fitzroy, VIC, Australia
  3. School of Health and Behavioural Sciences, Australian Catholic University, Strathfield, NSW, Australia
  4. School of Health and Behavioural Sciences, Australian Catholic University, Fitzroy, VIC, Australia
  5. Department of Nutrition, Dietetics and Food, Monash University, Melbourne, VIC, Australia

Background: Glucagon-like peptide-1 receptor agonist (GLP-1RA) medications induce substantial weight loss; however, changes in dietary intake and diet quality during treatment remain poorly understood1-4. This study quantified changes in dietary intake and diet quality during the first 12-weeks of GLP-1RA treatment among Australian adults living with obesity.

Methods: A 12-week pre-post, repeated measures study was conducted in adults commencing GLP-1RA treatment. Participants were recruited via St Vincent’s Hospital Weight Management Clinic, Melbourne and social media advertising. Participants completed up to three Intake24 dietary recalls at baseline, week two, month one and month three to quantify energy (kJ/d), macro- and micronutrient intake. Diet quality was assessed via Healthy Eating Index For Australians (HEIFA-2013). Change over time in dietary intake and HEIFA scores was assessed using linear mixed-effects models, with Bonferroni correction post-hoc comparisons where a significant time effect was found. Statistical significance was set at p<0.05.

Results: Of the 36 participants recruited, 32 commenced the medication. 88% (n=28) completed dietary data at baseline, 72% (n=23) at month three. Dietary intake significantly decreased in the first two weeks for total energy (-2570±5084kJ/d, p=0.02), total fat (-31±46g/d, p=0.02), saturated fat (-15±21g/d, p=0.01) and sodium (-696±1080mg/d, p=0.03), from baseline to month one for protein (-17±26g/d, p=0.03) and baseline to month three for total energy (-2378±3333kJ/d, p=0.02) and carbohydrates (-61±94g/d, p=0.03). Dietary fibre remained suboptimal throughout (17±8g/d at baseline; 13±8g/d at month 3). HEIFA scores were not significantly different across the trial (baseline=46±13; month three=50±10, p=0.28).

Conclusion: GLP-1RA treatment was associated with marked reductions in dietary intake, particularly during the first two weeks of therapy; however, diet quality did not change. These findings identify the early treatment period as a critical opportunity for targeted dietary support, with consideration of diet quality, to optimise nutritional adequacy during GLP-1RA therapy.

  1. Jansson AK, Gómez-Martín M, Hedin L, et al. A Systematic Review Identifying Critical Evidence Gaps in Reporting Dietary Change in Randomized Controlled Trials Prescribing Liraglutide, Semaglutide, or Tirzepatide. Obes Rev. 2026;27(6):e70077. doi:10.1111/obr.70077
  2. Babazadeh D, Wyatt S, Steinberg FM. Examining the Omission of Dietary Quality Data in Glucagon-Like Peptide 1 Clinical Trials: A Scoping Review. Adv Nutr. 2025;16(10):100491. doi:10.1016/j.advnut.2025.100491
  3. Moiz A, Filion KB, Tsoukas MA, Yu OH, Peters TM, Eisenberg MJ. Mechanisms of GLP-1 Receptor Agonist-Induced Weight Loss: A Review of Central and Peripheral Pathways in Appetite and Energy Regulation. Am J Med. 2025;138(6):934-940. doi:10.1016/j.amjmed.2025.01.021
  4. Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional priorities to support GLP-1 therapy for obesity: A joint Advisory from the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and The Obesity Society. Obesity (Silver Spring). 2025;33(8):1475-1503. doi:10.1002/oby.24336