FastForward: A Prospective Analysis of Long-term Fasting and Subsequent Food Reintroduction in Humans

This study explores what happens in the body and wellbeing during and after a period of long-term fasting. At the Buchinger Wilhelmi Clinic, participants follow a medically supervised fasting program lasting five or more days, followed by a structured food reintroduction phase. The study observes participants over time to better understand how fasting and the return to eating affect weight, metabolism, nutrition habits, and overall well-being. All participants will complete online questionnaires during the fasting phase and for up to three months afterward. These surveys help track changes in lifestyle, mood, and health. In addition during the first two weeks after fasting ends participants wear a continuous glucose monitor (CGM) to track blood sugar levels in real time, use a mobile app to document meals with photos, and perform simple at-home blood tests using dried blood spot (DBS) kits. By combining digital tools with personal reports and at home tests, the study aims to gain a clearer picture of how the body adapts after a prolonged fast. The goal is to better understand the short- and medium-term effects of extended fasting on metabolism, diet, and well-being-and to provide practical guidance for those interested in fasting as a health practice.

NCT Number	NCT07155993
Lead Sponsor	Buchinger Wilhelmi Development & Holding GmbH Collaborators: ETH Zurich
Conditions	Diabetes (DM), Pre Diabetes, Overweight (BMI > 25)
Enrollment	300 participants
Start Date	2024-08-01
Primary Completion	2026-08 (estimated)
Study Completion	2026-12 (estimated)
Updated on ClinicalTrials.gov	2025-09-10