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

Exploring the effects of calorie restriction with and without time-restricted eating on immune profiles and gut microbiota in adults at risk of type 2 diabetes (144904)

Laurent Turner 1 , Feargal Ryan 2 , Yilin Tong 1 , Athena Variji 1 , You Jin Chang 1 , Kai Liu 1 , Xiao Tong Teong 1 , Lijun Zhao 2 , Gary Wittert 1 , Amy Hutchison 1 , Stephen Blake 2 , Leonie Heilbronn 1
  1. Adelaide University, Adelaide, SA, Australia
  2. Flinders University , Adelaide, SA, Australia

Background: Calorie restriction (CR) can modulate immune function. However, whether time-restricted eating (TRE) extends the benefits of CR on markers of immune and gut health is unknown.

Objective: To explore the effects of early (eCR) and delayed (dCR) calorie restriction versus CR alone on peripheral leukocytes and gut microbiota characteristics in adults at risk of type 2 diabetes. 

Methods: 114 adults (Female/Male 91/23; 59±9 years; BMI 32.1±4.6 kg/m²) with elevated waist circumference and fasting glucose (≥5.6 mmol/L) were stratified by sex and fasting glucose and randomized (1:1:1) to 30% CR as early (eCR; 0800-1600), delayed (dCR; 1200-2000), or unrestricted CR for 8 weeks. Blood samples were collected every 4 hours during a 26-hour ward visit at baseline and week 8. Spectral flow cytometry was used to assess leukocyte abundance and function. After trial commencement, faecal samples were collected at baseline and week 8, with 71 participants assessed using shotgun metagenomics sequencing. Linear mixed models assessed fasting immune cell abundance and function, adjusting for covariates. Mesor, amplitude and acrophase of immune outcomes were estimated using cosinor analysis. Paired Wilcoxon rank-sum tests were used to assess gut microbiota composition and function.

Results: In the fasted state, the counts of neutrophils, CD56dimCD16bright natural killer (NK) cells, non-classical monocytes decreased, while the count of unswitched memory B cells increased (q<0.05). The abundance of innate and effector leukocytes expressing markers for activation, exhaustion, cytotoxicity, and proliferation also decreased (q<0.05). Mesor for neutrophils, NK cell subsets and monocyte subsets decreased, while the mesor of switched memory B cells increased (q<0.05). Mesor for all functional markers decreased across innate and effector leukocytes (q<0.05). No between-group differences were detected in any parameter. Gut microbiota composition and function remained unchanged.

Conclusions: CR decreased the 24h abundance and activation of innate and effector immune cells, while preserving or enhancing memory B cell populations. TRE did not confer additional benefits.