NCT07434349

Exercise Timing and Postprandial Glucose Responses

Exercise Timing and Postprandial Glucose Responses in Healthy Adults

• Status: Not Yet Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 30 (estimated)
• Sponsor: Technical University of Munich · Academic / Other
• Sex: All
• Age: 18 Years – 30 Years
• Healthy volunteers: Accepted

Summary

This interventional crossover study examines the effect of exercise timing relative to meal intake on postprandial glucose responses in healthy, physically active young adults. Participants complete five experimental conditions involving endurance exercise performed before or after breakfast or dinner, as well as a non-exercise control condition, while wearing a continuous glucose monitoring device. Postprandial glucose responses are assessed for the three consecutive meals following each exercise session. Following morning exercise, outcomes are assessed after breakfast, lunch, and dinner on the same day. Following evening exercise, outcomes are assessed after dinner on the same day and after breakfast and lunch on the subsequent day. All meals are standardized and consumed at fixed clock times.

Detailed description

This study is conducted as a repeated measures, randomized crossover trial. Each participant completes five intervention conditions within a 14 day study period while wearing a continuous glucose monitoring device. The order of conditions is randomized, and all participants complete all conditions. The five conditions include endurance exercise performed before breakfast, after breakfast, before dinner, after dinner, and a recovery day without exercise. On exercise days, participants complete a 45 minute outdoor run at a vigorous intensity at predefined times relative to standardized meals. Breakfast, lunch, and dinner are consumed at fixed clock times (08:00, 13:00, and 18:00, respectively). Postprandial glucose outcomes are assessed for the three consecutive meals following each exercise session. In conditions involving exercise performed before or after breakfast, outcomes are assessed following breakfast, lunch, and dinner on the same day. In conditions involving exercise performed before or after dinner, outcomes are assessed following dinner on the same day and following breakfast and lunch on the subsequent day. Dietary intake is fully standardized across all intervention days. Meal composition is identical across intervention days within participants, with macronutrient composition held constant. Meals are designed to have a high glycemic load, calculated using published glycemic index tables and established food composition databases. Meals must be consumed within a predefined consumption window, with the start of meal intake serving as the reference time point for postprandial glucose analyses. Adherence to meal timing and consumption is verified using time-stamped photographs of meals and packaging, along with a standardized checklist documenting consumption times. Habitual waking times compatible with the fixed breakfast time are required for study participation. During the intervention period, participants are instructed to standardize bedtime as closely as possible across study days and to record wake time and sleep duration daily by self-report. Caffeine consumption is restricted on intervention days and on the day preceding each intervention day. On the day before each intervention day, participants are also instructed to refrain from structured exercise and alcohol. Participants are further instructed to replicate, as closely as possible, the type and timing of meals consumed on the day preceding each intervention condition in order to standardize pre-intervention nutritional status. This applies particularly to the day before conditions involving morning exercise and to earlier meals consumed on days with evening exercise. All exercise sessions are completed outdoors on the same route. Ambient temperature and precipitation are recorded for each exercise session using smartphone-based weather data. Exercise sessions may be rescheduled in cases of extreme weather conditions or acute illness to ensure participant safety and protocol consistency.

Conditions

• Exercise Timing
• Postprandial Glucose

Interventions

Type	Name	Description
BEHAVIORAL	Timed Endurance Exercise	The exercise intervention consists of a 45 minute continuous outdoor run performed on a standardized route. Participants are instructed to maintain a consistent running pace across all exercise conditions. Exercise intensity is standardized using a target heart rate corresponding to 75 to 85 percent of maximal heart rate, and participants must be able to complete 45 minutes of continuous running at this intensity without stopping. Heart rate, duration, distance, and pace are recorded using a heart rate monitor and GPS enabled device. Ambient temperature and precipitation are recorded for each session. Exercise sessions may be rescheduled in cases of extreme weather or acute illness.
BEHAVIORAL	No Exercise Control	This intervention involves a non-exercise control condition

Timeline

• Start date: 2026-03-01
• Primary completion: 2026-08-01
• Completion: 2026-08-01
• First posted: 2026-02-25
• Last updated: 2026-02-25

Locations

1 site across 1 country: Germany