PP349 - GLYCAEMIC DYNAMICS DURING FOOD REINTRODUCTION AFTER LONG-TERM THERAPEUTIC FASTING: A CGM STUDY

PP349

GLYCAEMIC DYNAMICS DURING FOOD REINTRODUCTION AFTER LONG-TERM THERAPEUTIC FASTING: A CGM STUDY

M. Knufinke^1,2,*, E. K. Stroppel², A. Siegler², F. von Meyenn¹, R. Mesnage^2,3

¹Department of Health Sciences and Technology, Laboratory of Nutrition and Metabolic Epigenetics, ETH Zürich, Zürich, Switzerland, ²Scientific Department, Buchinger Wilhelmi Clinic, Überlingen, Germany, ³Department of Nutritional Sciences, School of Life Course Sciences, Faculty of Life Sciences and Medicine, King´s College London, London, United Kingdom

Rationale: Long-term therapeutic fasting improves metabolic parameters, yet glycaemic dynamics during food reintroduction remain uncharacterised. We provide the first day-by-day continuous glucose monitoring (CGM) description of this transition.

Methods: In this prospective observational study (FastForward), 173 participants underwent medically supervised Buchinger Wilhelmi fasting (mean 9.4±4.1 days) followed by structured food reintroduction. Day 1 was low-calorie (<400 kcal); Day 2 introduced 800 kcal (~45% carbohydrate [CHO], or ~15% CHO in a ketogenic subgroup, n=24). CGM (FreeStyle Libre) was applied from Day 1 for 13 days. Daily metrics: mean glucose, coefficient of variation (CV%) and mean amplitude of glycaemic excursions (MAGE). Venous HbA1c was measured pre-fast (T0), at end-of-fast (T1), and after 1–4 days of in-clinic food reintroduction (T2; n=263). Paired t-tests with Bonferroni correction.

Results: Mean weight loss was 3.75±2.23 kg. HbA1c decreased from T0 to T1 (Δ=−0.17%, p<0.001, d=0.75) and was maintained at T2 (ns). On CGM, mean glucose rose from 94.8±17.2 mg/dl (Day 1) to 112.3±14.8 mg/dl (Day 13, p<0.001 from Day 4). Glycaemic variability peaked on Day 2, the first full caloric day (800 kcal, 45% CHO), with CV 20.1% and MAGE 42.5 mg/dl, declining to 13.4% and 30.3 mg/dl by Day 13 (p<0.001 vs Day 1). In the ketogenic subgroup, the Day-2 peak was attenuated (CV 13.6% vs 21.0%), suggesting CHO load as the primary driver.

Conclusion: These results demonstrate that the post-fast reintroduction phase carries a distinct, time-limited glycaemic risk window on Day 2 that clinicians and patients should anticipate. The fasting-induced HbA1c reduction persists through in-clinic reintroduction, and the attenuated response in the ketogenic subgroup suggests that reintroduction diet composition may modulate this window. 

Disclosure of Interest: M. Knufinke Other: Employed by the Buchinger Wilhelmi Development & Holding GmbH, E. Stroppel Other: Employed by the Buchinger Wilhelmi Development & Holding GmbH, A. Siegler Other: Employed by the Buchinger Wilhelmi Development & Holding GmbH, F. von Meyenn: None declared, R. Mesnage Other: Employed by the Buchinger Wilhelmi Development & Holding GmbH