Fasting, Fed
Conditions
Keywords
breath acetone, energy balance
Brief summary
This study aims at assessing whether breath acetone concentration is a good bio-marker of instantaneous energy balance in healthy subjects.
Detailed description
Each participant will be studied on three occasions, separated by 1-4 weeks. Each evaluation will consist in the same set of metabolic measurements, but will be performed fasting or during administration of a 70% fat or 70% carbohydrate liquid diet, according to a randomized order. On each occasion, subjects will consume a standardized dinner the day before the experiment. They will remain fasted since 10 pm until the test day. On the day of the experiments, one venous cannula will be inserted into a forearm vein for the collection of blood samples. An indirect calorimetry (measurement of respiratory gas exchanges using a ventilated canopy at rest, or a face mask during exercise) will be performed throughout the 6-hour test to measure energy expenditure and net substrate oxidation rate. Blood samples will be obtained every 60 min for the measurement of plasma glucose, insulin, free fatty acids, and beta-hydroxybutyrate concentrations. Breath samples will be also collected every 60 min (in 500 ml sampling bag) for the measurement of breath acetone concentration using a novel gas analyzer based on infrared laser spectroscopy. Measurements will be done during 3 consecutive periods: * 0-120 min: Fast + Rest: subjects will remain lying in bed in fasting conditions (negative energy balance). * 120-360 min: Fed + Rest: subjects will remain in bed in a fasting state (C) or will receive every hour a liquid meal containing either 70% fat, 15% carbohydrate and 15% protein (Fat), or 70% carbohydrate, 15% fat and 15% protein (Sugar), corresponding to 1.5 X hourly resting energy requirement (positive energy balance). * 360-480 min: Fed + Exercise: subjects will be transferred to an ergometric bicycle and will be asked to bike at a power output of 25 W \[i.e. increasing total energy expenditure to ca. 2 time resting energy expenditure (negative energy balance)\].
Interventions
OTHERFasting condition
Subjects will fast over the whole experimental period (480 min)
OTHERSugar condition
After a 2-h fasting state, subjects will ingest every hour a drink containing 70% carbohydrate, 15% fat and 15% protein and providing 1.5 X hourly resting energy requirement.
OTHERFat condition
After a 2-h fasting state, subjects will ingest every hour a drink containing 70% fat, 15% carbohydrate and 15% protein and providing 1.5 X hourly resting energy requirement.
Sponsors
Empa - Swiss Federal Laboratories for Materials Testing and Research, Zürich
University of Lausanne
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Subject)
Eligibility
Sex/Gender
ALL
Age
18 Years to 60 Years
Healthy volunteers
Yes
Inclusion criteria
* BMI 19.5-29.9 kg/m2, * Healthy
Exclusion criteria
* any known disease (with the exception of allergies); * consumption of alcohol \> 40 g/day; * any current drug treatment (with the exception of contraceptive agents, antihistaminergic drugs for allergies, or multivitamin supplementations), * history of lactose intolerance, * history of exercise intolerance.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Breath acetone | Every 60 min from 0 to 420 min | Changes in breath acetone concentrations in conditions of positive vs. negative energy balance. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Plasma parameters | Every 60 min from 0 to 420 min | Relationship between breath acetone and plasma beta-hydroxybutyrate, glucose, free fatty acids and insulin concentrations |
Countries
Switzerland
Outcome results
None listed