Mechanisms of Fasting Induced Reduction in Energy Expenditure

Study Overview
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Brief Summary
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Fasting reduces the energy consumption of the human body. The extent of this adaptation varies significantly between different individuals. The aim of this research project is to investigate how this adaptation of the metabolism is regulated by the body. For this purpose, we will first measure how the so-called basal metabolic rate of the body reacts to a short-term fasting of 24 h in a preliminary study. Those subjects with a particularly pronounced and those subjects with an only slightly pronounced reaction of the basal metabolic rate will be invited to the main study. Here, in random order (24 h fasting vs. 8 h fasting), the following is compared how the basal metabolic rate of the body reacts to the reduced energy intake. how the energy metabolism increases after a test meal what role in particular the thyroid hormones play in this adaptation. In addition, a sample of the subcutaneous adipose tissue is taken in each case and it is examined how the regulation of metabolic processes at the cellular level.

Official Title
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Mechanisms of Fasting Induced Reduction in Energy Expenditure - FIRE Trial

Conditions
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Fasting

Intervention / Treatment
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* Other: mixed meal test


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age: 18 to 40 years Body mass index 18.0 to 27.0 kg/m² Exclusion Criteria: Chronic conditions necessitating medical treatment (e.g., renal failure, hepatic dysfunction, cardiovascular disease, diabetes mellitus), Known or suspected non-compliance, drug or alcohol abuse, Inability to follow the procedures of the study Participation in another study with investigational drug within the 30 days preceding and during the present study, Previous enrolment into the current study, Enrolment of the investigator, his/her family members, employees and other dependent persons, Hypothyroidism or hyperthyroidism Pregnant, breastfeeding and menopausal women

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: randomized, open label, cross-over, monocentric trial in healthy volunteers
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Fasting for 24 hours<br> | Other: mixed meal test<br>* mixed meal test after fasting<br>|
| Other: Fasting for 8 hours<br> | Other: mixed meal test<br>* mixed meal test after fasting<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change of energy expenditure (EE) determined by indirect calorimetry (kcal per 24h) | Difference of EE (determined by indirect calorimetry) between baseline and 60 minutes after ingestion of the liquid test meal. Both measurements will be performed after an overnight fasting period. | 60 minutes after ingestion of test meal | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Level of free thyroxine | The thyroid hormone (TH) system is an important regulator of EE. We hypothesize that levels of TH are higher in the spendthrift than in the thrifty group. | after 24 hours and after 12 hours of fasting | 
| Level of free triiodothyronine | The thyroid hormone (TH) system is an important regulator of EE. We hypothesize that levels of TH are higher in the spendthrift than in the thrifty group. | after 24 hours and after 12 hours of fasting | 
| Respiratory quotient (RQ) | We hypothesize that the participants in the thrifty group have a lower proportion of fatty acid metabolism and therefore a higher RQ. | after 24 hours and after 12 hours of fasting | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Thermogenesis