Exercise Timing and Postprandial Glucose Responses (ExTime-Glu)

Exercise Timing and Postprandial Glucose Responses in Healthy Adults

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.

Study Overview

• Status: Recruiting
• Conditions: Postprandial Glucose; Exercise Timing
• Intervention / Treatment: Behavioral: Timed Endurance Exercise; Behavioral: No Exercise Control

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.

• Study Type: Interventional
• Enrollment (Estimated): 30
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Christoph Höchsmann, PD Dr.; Phone Number: +49 89 289 24488; Email: christoph.hoechsmann@tum.de
• Study Contact Backup: Name: Karsten Köhler, Prof. Dr.; Email: karsten.koehler@tum.de

Study Locations

• Germany
  • Bavaria
    • München, Bavaria, Germany, 80809
      • Recruiting
      • Technical University of Munich
      • Contact: Christoph Höchsmann, PD Dr.; Phone Number: +49 89 289 24488; Email: christoph.hoechsmann@tum.de

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Age 18 to 35 years
• Body mass index 18.5 to 24.9 kg per square meter
• Able to complete 45 minutes of continuous running at an intensity corresponding to 75 to 85 percent of maximal heart rate without stopping
• Engages in regular endurance-type physical activity
• Habitual waking times are compatible with the fixed breakfast time of 08:00
• Willing and able to comply with all study procedures, including standardized meals, exercise sessions, behavioral restrictions, and continuous glucose monitoring
• For female participants: non-pregnant and using stable hormonal contraception for at least 3 months

Exclusion Criteria:

• Acute or chronic illness
• Metabolic disorders or conditions associated with altered glucose or lipid metabolism
• Use of medications known to interfere with glucose metabolism or study outcomes
• Intolerance or allergy to components of the standardized study diets
• Pregnancy or breastfeeding
• Body mass index greater than or equal to 25 kg per square meter
• Current or past eating disorder, or any medical condition or medication that could affect appetite regulation, glucose regulation, or make vigorous endurance exercise unsafe
• Current smoking or use of nicotine-containing products

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Run Before Breakfast; Participants complete a 45 minute outdoor run beginning 60 minutes before the standardized breakfast time (08:00). A short recovery period is allowed between completion of exercise and meal initiation. Postprandial glucose responses are assessed following breakfast, lunch (13:00), and dinner (18:00).	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.
Experimental: Run After Breakfast; Participants complete a 45 minute outdoor run beginning 90 minutes after the start of breakfast (08:00). Postprandial glucose responses are assessed following breakfast, lunch (13:00), and dinner (18:00).	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.
Experimental: Run Before Dinner; Participants complete a 45 minute outdoor run beginning 60 minutes before the standardized dinner time (18:00). Postprandial glucose responses are assessed following dinner on the same day and following breakfast (08:00) and lunch (13:00) on the subsequent day.	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.
Experimental: Run After Dinner; Participants complete a 45 minute outdoor run beginning 90 minutes after the start of dinner (18:00). Postprandial glucose responses are assessed following dinner on the same day and following breakfast (08:00) and lunch (13:00) on the subsequent day.	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.
Experimental: No Exercise Control; Participants do not perform structured exercise on this study day and follow the standardized meal schedule. This condition serves as a within participant control. Postprandial glucose responses are assessed following breakfast (08:00), lunch (13:00), and dinner (18:00).	Behavioral: No Exercise Control; This intervention involves a non-exercise control condition

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
3-hour postprandial glucose area under the curve (AUC)	The area under the curve for interstitial glucose concentration during the 3-hour period following each of the three consecutive meals assessed after each exercise or control condition, measured using continuous glucose monitoring.	During each intervention condition within the 14-day study period, assessed over the 3-hour period following each of the three consecutive meals after each condition

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Incremental postprandial glucose AUC	Incremental area under the curve for interstitial glucose concentration during the 3-hour postprandial period following each assessed meal, calculated relative to pre-meal baseline glucose concentration.	During each intervention condition within the 14-day study period, assessed over the 3-hour period following each of the three consecutive meals after each condition
Peak postprandial glucose concentration	Maximum interstitial glucose concentration following each meal.	During each intervention condition within the 14-day study period, assessed over the 3-hour period following each of the three consecutive meals after each condition
Time to peak glucose	Time from meal initiation to peak interstitial glucose concentration.	During each intervention condition within the 14-day study period, assessed over the 3-hour period following each of the three consecutive meals after each condition
Subjective appetite ratings	Subjective sensations of hunger, fullness, prospective food consumption, desire to eat, nausea, and thirst are assessed using electronic 100-mm visual analog scales administered before and after each meal and each exercise session.	Repeatedly during each intervention condition within the 14-day study period, assessed before and after each meal and exercise session
Rating of perceived exertion	Perceived exertion following each exercise session is assessed using the Borg Rating of Perceived Exertion scale (6-20).	Immediately after each exercise session during each intervention condition within the 14-day study period

Collaborators and Investigators

• Sponsor: Technical University of Munich
• Investigators: Principal Investigator: Christoph Höchsmann, PD Dr., Technical University of Munich

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2026
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): August 1, 2026

Study Registration Dates

• First Submitted: February 12, 2026
• First Submitted That Met QC Criteria: February 19, 2026
• First Posted (Actual): February 25, 2026

Study Record Updates

• Last Update Posted (Actual): April 20, 2026
• Last Update Submitted That Met QC Criteria: April 15, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Continuous Glucose Monitoring; Endurance Exercise; Glycemic Response; Postprandial Glucose; Exercise Timing
• Other Study ID Numbers: ExTime-Glu

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: Individual participant data will be shared upon reasonable request in accordance with the Technical University of Munich's data sharing policy and applicable data protection regulations.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No