Time-of-Day Effects of Fasted Exercise on Energy Intake

Effects of Fasted Morning vs. Evening Exercise on Post-Exercise Energy Intake

This trial's aim is to investigate the time-of-day effects (morning vs. evening) of fasted exercise on acute and 24h post-exercise energy intake. Specifically, we will compare the effects of fasted morning exercise (12h overnight fast) vs. fasted (6h and 12h) evening exercise on total energy intake during a post-exercise ad libitum test meal as well as on 24h (free-living) energy intake. The secondary aim is to assess subjective appetite ratings before, immediately after, and 30 min post-exercise (visual analog scale). Healthy men and women aged 18-30 years will be included.

Study Overview

• Status: Completed
• Conditions: Energy Intake; Health; Appetite; Eating Behaviors
• Intervention / Treatment: Behavioral: Fasted Morning Exercise (12h); Behavioral: Fasted Evening Exercise (6h); Behavioral: Fasted Evening Exercise (12h); Behavioral: Fed Morning Exercise (AMEx Fed); Behavioral: Evening Fed Exercise (PMEx Fed)

Detailed Description

In a five-way crossover design, participants will complete three fasted and one non-fasted exercise sessions on a treadmill in randomized order on weekdays with one week in between sessions: once in the morning (~1h after participants' habitual wake-up time) following a 12h overnight fast (12h AMEx), once in the evening (exactly 12h after the 12h AMEx condition) after a 6h fast (6h PMEx), and once in the evening (identical to the 6h PMEx condition) following a 12h fast (12h PMEx). As control conditions, a subsample of participants (n=17) will also complete a fed morning exercise condition (AMEx Fed; identical timing to 12h AMEx) and a fed evening exercise condition (PMEx Fed; identical timing to 12h PMEx), following a small pre-exercise snack (~10% of individual energy requirements; 30 min before exercise). The standardized meals provided before the fasting period contained 30% of the individual's daily energy requirements and consisted of ~50% carbohydrates, ~30% fat, and ~20% protein.

• Study Type: Interventional
• Enrollment (Actual): 35
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Germany
  • Bavaria
    • Munich, Bavaria, Germany, 80809
      • Technical University of Munich

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• BMI of 18.5.0-30.0 kg/m2
• weight stability (≤2.5 kg weight change during the past 3 months)
• ability to exercise at a vigorous intensity for 30 minutes

Exclusion Criteria:

• pregnancy or breastfeeding
• smoking
• history of or current eating disorders
• medical condition or use of medication that could affect appetite or pose any contraindications to exercise

As the menstrual cycle can cause fluctuations in food cravings and appetite, women of childbearing age were only eligible if they used hormonal contraceptives. To ensure constant exposure to exogenous estrogen and progestin throughout the study phase, participating women were further asked to use active hormone pills throughout the study period in both studies, a practice that is considered both safe and efficacious.

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Study Plan

How is the study designed?

Design Details

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

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Fasted Morning Exercise (12h AMEx); Exercise will take place in the morning, following a 12h overnight fast	Behavioral: Fasted Morning Exercise (12h); A 30-minute exercise session will take place on a treadmill in the morning (7:00, ~1h after participants' habitual wake-up time), after a 12h overnight fast. The session will consist of 30 minutes of steady state cycling at 65% of VO2max, following a 5 min warm-up.
Active Comparator: Fasted Evening Exercise (6h PMEx); Exercise will take place in the evening, following a 6h period of fasting	Behavioral: Fasted Evening Exercise (6h); A 30-minute exercise session will take place on a treadmill in the evening (19:00, exactly 12 hours after the morning session), after a 6h fasting period. The session will consist of 30 minutes of steady state cycling at 65% of VO2max, following a 5 min warm-up.
Active Comparator: Fasted Evening Exercise (12h PMEx); Exercise will take place in the evening, following a 12h period of fasting	Behavioral: Fasted Evening Exercise (12h); A 30-minute exercise session will take place on a treadmill in the evening (19:00, exactly 12 hours after the morning session), after a 12h fasting period. The session will consist of 30 minutes of steady state cycling at 65% of VO2max, following a 5 min warm-up.
Active Comparator: Fed Morning Exercise (AMEx Fed); Exercise will take place in the morning after consuming a small snack (30 min before exercise)	Behavioral: Fed Morning Exercise (AMEx Fed); A 30-minute exercise session will take place on a treadmill in the morning (7:00, ~1h after participants' habitual wake-up time), after consuming a small pre-exercise snack (30 min before exercise). The session will consist of 30 minutes of steady state cycling at 65% of VO2max, following a 5 min warm-up.
Active Comparator: Fed Evening Exercise (PMEx Fed); Exercise will take place in the evening after consuming a small snack (30 min before exercise)	Behavioral: Evening Fed Exercise (PMEx Fed); A 30-minute exercise session will take place on a treadmill in the evening (19:00, exactly 12 hours after the morning session), after consuming a small pre-exercise snack (30 min before exercise). The session will consist of 30 minutes of steady state cycling at 65% of VO2max, following a 5 min warm-up.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Acute ad-libitum post-exercise energy intake (test meal)	Acute post-exercise energy intake (kcal) will be measured objectively using a single-item ad libitum test meal occurring 30 minutes after each exercise session. The meal will consist of cheese pizza, offered in excess of individual daily energy requirements, and all food will be provided at once.	30 minutes after exercise

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
24h post-exercise energy intake	Post-exercise energy intake (ad libitum) will be self-reported (weighed food log) during the 24 hours following the exercise session. For the 6h PMEx and 12h PMEx conditions, this will encompass all food consumed after the exercise session until 19:00 the next day, including the test meal and typically the next day's breakfast, lunch, dinner, and all snacks consumed during this period. For the 12h AMEx condition, the 24-hour post-exercise period will encompass the test meal and typically lunch, dinner, snacks on the day of exercise, and the next day's breakfast, with the observation period ending at 07:00.	24 hours post-exercise
Carbohydrate oxidation	Carbohydrate oxidation, measured via indirect calorimetry	continuously throughout the 30-minute exercise bout
Fat oxidation	Fat oxidation, measured via indirect calorimetry	continuously throughout the 30-minute exercise bout
Energy expenditure	Energy expenditure, measured via indirect calorimetry	continuously throughout the 30-minute exercise bout
Subjective appetite measures	At each study condition visit, participants will rate their subjective perception of hunger, fullness, and desire to eat, and prospective food consumption on a 100mm visual analog scale anchored from "not at all" to "extremely" before each exercise session (Pre), immediately after (Post), and after an additional 30 minutes of post-exercise rest (Post30, immediately before the test meal),	before exercise, immediately after exercise, and 30 minutes after exercise

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Blood glucose	Blood glucose measured via capillary blodd (finger prick)	before exercise and immediately after exercise
Blood lactate	measurement via capillary blood from the ear lobe	before exercise and immediately after exercise
Breath ketones	breath analysis via Lumen (MetaFlow Ltd) device	before and immediately after exercise
Blood ketones	measured via capillary blood (finger prick) and Freestyle Precision Neo (Abbott).	before exercise and immediately after exercise

Collaborators and Investigators

• Sponsor: Technical University of Munich

Study record dates

Study Major Dates

• Study Start (Actual): April 1, 2025
• Primary Completion (Actual): November 30, 2025
• Study Completion (Actual): December 15, 2025

Study Registration Dates

• First Submitted: April 14, 2025
• First Submitted That Met QC Criteria: April 24, 2025
• First Posted (Actual): April 27, 2025

Study Record Updates

• Last Update Posted (Actual): February 6, 2026
• Last Update Submitted That Met QC Criteria: February 4, 2026
• Last Verified: July 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Behavior; Behavior, Animal; Feeding Behavior
• Other Study ID Numbers: MvE_FastEx

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: IPD will be shared upon reasonable request per the Technical University of Munich's data sharing policy.

Drug and device information, study documents

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