Clinical Trial Details
— Status: Recruiting
Administrative data
NCT number |
NCT04935983 |
Other study ID # |
NL72841.081.20 |
Secondary ID |
|
Status |
Recruiting |
Phase |
N/A
|
First received |
|
Last updated |
|
Start date |
September 1, 2020 |
Est. completion date |
April 2022 |
Study information
Verified date |
June 2021 |
Source |
Wageningen University |
Contact |
n/a |
Is FDA regulated |
No |
Health authority |
|
Study type |
Interventional
|
Clinical Trial Summary
It is well known that, even in quite homogenous populations, inter-individual variability in
fat oxidation during exercise, in particular MFO, is quite large. Individual factors like
gender, body composition (lean mass) and fitness level do explain a substantial part of this
variation. In addition, genetic factors do underlie differences between individuals. But also
'external factors' like nutritional status, i.e. a low or high carbohydrate (CHO)
availability, and exhaustion are likely linked to maximal fat oxidation, due to alterations
in substrate availability. The contribution of these external factors to alterations in
substrate utilization is, as of yet, unknown.
This study aims to establish the impact of pre-exercise CHO availability and exhaustion on
maximal fat oxidation (MFO & FATmax) during exercise
Description:
Rationale: During exercise, energy expenditure increases dramatically, with exercise
intensity as the single most important factor influencing substrate utilization. It is
commonly reported that fat oxidation increases as exercise intensity increases, up to a
certain point. At higher exercise intensities, fat oxidation declines quite rapidly, despite
increased energy requirements, and carbohydrate becomes the predominant, and finally the only
fuel source during (aerobic) exercise.
The maximal capacity of the human body to oxidize fat during exercise can quantitatively be
described by the so-called 'MFO' and 'FATmax'. The MFO (maximal fat oxidation) is the highest
absolute level of fat oxidation as expressed in gram per minute (g/min), while FATmax is the
exercise intensity at which fat oxidation is highest (%VO2max or %HFmax). These concepts may
have importance for endurance training and performance.
It is well known that, even in quite homogenous populations, inter-individual variability in
fat oxidation, in particular MFO, is quite large. Individual factors like gender, body
composition (lean mass) and fitness level do explain a substantial part of this variation. In
addition, genetic factors do underlie differences between individuals. But also 'external
factors' like nutritional status, i.e. a low or high carbohydrate (CHO) availability, and
exhaustion are likely linked to maximal fat oxidation, due to alterations in substrate
availability. The contribution of these external factors to alterations in substrate
utilization is, as of yet, unknown.
Objective: The investigators aim to establish the impact of pre-exercise CHO availability and
exhaustion on maximal fat oxidation (MFO & FATmax) during exercise.
Study design: The study consist of two parts. In part I the impact of carbohydrate
availability will be assessed, in part II the impact of exhaustion.
In part I (cross-over design) subjects will perform an graded exercise test to measure
maximal fat oxidation ('fatmax test'). At one occasion with low CHO, the other time with high
CHO. The order will be randomised. One week will be considered in between conditions.
In part II (single-arm intervention), subjects will do the graded exercise test twice on a
single day, but now with an exhaustive exercise session ('training') of ~ 90 min in between,
to induce exhaustion In both parts, the experimental testing will be preceded by a visit in
which body composition is measured and subjects are familiarised to the test procedures. In
addition, a physical activity questionnaire and a 3 day food record will be taken.
The graded exercise test is the so-called 'fatmax test' as described by Achten and Jeukendrup
(2003). Participants start with a warming up at 95W (males) or 60 W (females), after which
intensity will be increased every 3 min with 35 W, till exhaustion. Heart rate as well as
oxygen consumption (VO2) and carbon dioxide production (VCO2) will be monitored, to obtain
fat oxidation rates and maximal aerobic capacity.
Study population: The population of this study will consist of both males and females, aged
20 to 35, with a BMI of 18.5 to 27 kg/m2. A participant should be recreationally active,
defined as minimal of 3 hours training per week, and a maximum of 10 hours a week. Their
sports activity should have an endurance component Participant do not smoke and are healthy,
and comply with the study procedures.
Intervention (treatment):
Part I: In this part of the study the pre-exercise availability of carbohydrates will be
manipulated. Before measuring maximal fat oxidation during exercise, subjects will be
randomly-assigned to a 36 hour period (i.e an afternoon, a single day plus a breakfast) of
either a low CHO / high fat diet (~65 %en by fat) or an equal energy (isocaloric), high
carbohydrate diet (~65 %en by CHO).
Part II: in this part the intervention is a 'training session' of 90 min at 60% Wmax, with
every 15 min a high intensity bout of exercise of 2 min (90%Wmax). This is to simulate a
training session, and induce exhaustion.
The day before the trials, participants have to refrain from exercise.
Main study parameters/endpoints: The main study parameters are the MFO and FATmax as assessed
with indirect calorimetry (VO2, VCO2) during a graded exercise test (35W/ 3min protocol). In
order to calculate MFO and FATmax, oxygen consumption (VO2) and CO2 production (VCO2) are
measured. From these values the respiratory exchange ration (RER) can be calculated, and fat
oxidation will be quantified according to the equations of Frayn.