The Effect of Hydration on Postprandial Metabolic Responses

Certain populations, such as industrial workers and endurance athletes are particularly susceptible to dehydration due to exposure to heat for long periods of time causing evaporative water loss via sweating. The physical and cognitive decrements associated with dehydration have been widely researched, however the effect of dehydration on metabolism is lesser known. As climate change is causing temperatures to rise, and metabolic diseases such as type 2 diabetes are more common, the effect of dehydration on metabolism, specifically glycemic response to meals, needs to be established for future recommendations in clinical, environmental and athletic settings.

Therefore, the aim of this study is to investigate the effect of acute exercise-induced dehydration on subsequent metabolic responses to feeding (i.e. glycaemia and insulinaemia).

Study Overview

• Status: Not yet recruiting
• Conditions: Glycaemia
• Intervention / Treatment: Other: Water intake; Other: Water restriction

• Study Type: Interventional
• Enrollment (Estimated): 16
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Lewis J James, PhD; Phone Number: +44 (0) 1509 226305; Email: L.James@lboro.ac.uk

Study Locations

• United Kingdom
  • Leicestershire
    • Loughborough, Leicestershire, United Kingdom, LE113TU
      • Loughborough University
      • Contact: Lewis J James; Phone Number: +44 (0) 1509 226305; Email: L.James@lboro.ac.uk

Participation Criteria

Eligibility Criteria

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

Description

Inclusion Criteria:

• Male or female
• Generally fit and healthy
• Participate in endurance or intermittent exercise at least 3 times a week or minimum of 150 minutes moderate intensity activity per week

Exclusion Criteria:

• < 18 or > 45
• Any health condition that may affect study outcomes (e.g., endocrine/liver/renal/cardiovascular disease)
• Any morbidity that affects ability to cycle
• Smoker or vaper

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

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Euhydrated; Light exercise in a hot environment with water ingested to fully replace sweat losses and maintain euhydration.	Other: Water intake; Water ingested to fully replace sweat losses during exercise.
Experimental: Hypohydrated; Light exercise in a hot environment with water restricted to induce hypohydration of ~3% body mass through sweating.	Other: Water restriction; Water restriction to induce hypohydration of ~3% body mass through sweat losses during exercise.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Plasma glucose	Measured using colorimetric assay from venous blood samples	6 hours

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Plasma insulin	Measured using ELISA from venous blood samples	6 hours
Plasma osmolality	Measured using freezing point depression from venous blood samples	6 hours
Plasma volume change	Determined from haemoglobin and haematocrit measures in blood samples collected before and after drink ingestion	6 hours
Urine volume	Determined from urine samples collected before and after exercise	6 hours
Body mass	Determined from weighing participants before and after exercise	6 hours
Urine specific gravity/osmolality	Determined from urine samples collected before and after exercise	6 hours
Thirst sensation	Measured via 100 mm visual analogue scales 0 mm = not at all thirsty 100 mm = extremely thirsty	6 hours
Hunger sensation	Measured via 100 mm visual analogue scales 0 mm = not at all hungry 100 mm = extremely hungry	6 hours
Fullness sensation	Measured via 100 mm visual analogue scales 0 mm = not at all full 100 mm = extremely full	6 hours
Core body temperature	Measured via ingestible pill	6 hours
Blood pressure	Measured via and automated sphygmomanometer	6 hours

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
N-back task for working memory (cognitive function)	The task will comprise three progressively harder memory loads (1-Back, 2-Back, 3-Back). Each stimulus type will be used in all memory loads. Participants will have to respond using the space bar when they see a stimulus that is presented one, two, or three steps previously, dependent on the load condition. Each phase will comprise 50 trials with ten targets presented centrally on a plain white screen. Each stimulus will be presented for 1000 ms unless the participant responds and in which case the next trial will begin. Commission errors and correct responses will be used as indices of performance. Commission errors occur when participants respond to non-targets.	3 hours
Go/no-go task for response inhibition (cognitive function)	Participants will be instructed to press the space bar when an image of a tree appears onscreen ("go" stimulus) and to inhibit responding when an image of a football is presented (the "no-go" stimulus). The task will comprise 200 trials, of which 10% will be no-go trials. Each trial will last 500 ms and will have a black image on a white background. The sequence of stimuli will be the same for each participant. In order to allow for pre-potent tendencies to develop, 50 go trials will precede the first no-go trial. Increased commission error responses (i.e. responding incorrectly on a no-go trial) will indicate reduced response inhibition. Commission errors and correct responses will be measured as indices of performance.	3 hours
Oculomotor function antisaccade task	Each trial will start with a 1-second instruction screen prompting participants to focus on the target. A central fixation point will be displayed for one second, followed by a brief blank interval and then the appearance of a red distractor. The distractor will appear randomly to the left or right of the fixation point and will remain visible for 2 seconds. Participants will be instructed to maintain fixation at the centre and then make a saccade in the opposite direction as soon as the distractor appears. The task will include 24 trials, with four additional practice trials. The primary variables measured will be reaction time mean and standard deviation, which reflect inhibition latency and variability. Antisaccade errors, or the number of incorrect saccades, will also be calculated.	3 hours
Oculomotor function prosaccade task	Each trial will begin with a 1-second instruction screen, followed by a central fixation point and a brief blank interval. A green target then will appear randomly to the left or right of the fixation point for 2 seconds. Participants will be instructed to fixate at the centre and then make a saccade towards the target. The task will include a total of 14 trials, with four additional practice trials. The variables measured will be reaction time mean and standard deviation, which indicate prosaccade latency and variability.	3 hours
Oculomotor function smooth pursuit task	A smooth pursuit task consists of participants following a stimulus with their eyes as it moves in an elliptical pattern on a screen. The stimulus is in motion for 60 seconds. The primary variable measured will be the variability in x and y coordinates of the left and the right eye.	3 hours

Collaborators and Investigators

• Sponsor: Loughborough University
• Collaborators: National Institute for Health Research Leicester Biomedical Research Centre

Study record dates

Study Major Dates

• Study Start (Estimated): March 1, 2025
• Primary Completion (Estimated): November 1, 2025
• Study Completion (Estimated): December 1, 2025

Study Registration Dates

• First Submitted: February 4, 2025
• First Submitted That Met QC Criteria: February 10, 2025
• First Posted (Actual): March 25, 2025

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: February 10, 2025
• Last Verified: February 1, 2025

More Information

Terms related to this study

• Keywords: Glucose control; Hydration; Dehydration; Glycemia; Glycaemia; Hypohydration
• Other Study ID Numbers: 2025-20370

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

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