AzTrials
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FastingFIRENCT06134258

Mechanisms of Fasting Induced Reduction in Energy Expenditure

A study testing mixed meal test in people with Fasting, run by ETH Zurich at 1 site in Switzerland.

Recruiting

Looking for participants now. Contact the study team or a site below to ask about taking part.

Sites and contacts
Official record
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Trial summary

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. Read more about this study

Who is it for?
Ages 18 to 40 yearsHealthy volunteers can take part
Conditions the study is for
Fasting
What is being tested?
mixed meal test
Could I receive a placebo?
No, everyone receives an active treatment
How many people
40 participants
Where
1 siteSwitzerland
Study dates
15 Nov 2023to 18 Apr 2026
Phase
Interventional
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 to 40 years
  • All sexes
  • Healthy volunteers accepted
  • Adult

Who may be able to join

  • Age: 18 to 40 years
  • Body mass index 18.0 to 27.0 kg/m²

Who cannot join

  • 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

Trial locations and contacts

1 site in 1 country. Contact the study team or a site near you to ask about taking part.

Matthias Betz contact

0041 61 265 2525

matthias.betz@usb.ch

Rahel Loeliger contact

0041 61 265 2525

Rahel.Loeliger@usb.ch

Switzerland1 site, 1 recruiting

  • University Hospital Basel

    Basel

    Rahel Loeliger, 0041 61 265 2525, Rahel.Loeliger@usb.ch

    Recruiting

Other trials in Switzerland

About this study

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

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.
Read the detailed description

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.

Conditions
Fasting
Being tested
mixed meal test
Keywords
Thermogenesis
Medical subject headings
Fasting

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • mixed meal testOther

    mixed meal test after fasting

Study groups in NCT06134258
Study groupRoleWhat they receive
Fasting for 24 hoursOtherFasting for 24 hours
Receives: Other: mixed meal test
Fasting for 12 hoursOtherFasting for 12 hours
Receives: Other: mixed meal test

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. 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.

    Measured: 60 minutes after ingestion of test meal

Secondary outcomes (3)

  1. 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.

    Measured: after 24 hours and after 12 hours of fasting

  2. 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.

    Measured: after 24 hours and after 12 hours of fasting

  3. 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.

    Measured: after 24 hours and after 12 hours of fasting

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted18 Nov 2023
  2. Study start15 Nov 2023
  3. Primary completion18 Apr 2026 (estimated)
  4. Study completion18 Apr 2026 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Basic science
Allocation
Randomised
Intervention model
Crossover
Model description
randomized, open label, cross-over, monocentric trial in healthy volunteers
Masking
None (open label)
Enrolment
40 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06134258
Sponsor's protocol ID
EKNZ_2023-01401
Acronym
FIRE
Status last verified
May 2025
First submitted
6 Nov 2023
Last updated
30 May 2025
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No

Publications

  • Hollstein T, Heinitz S, Basolo A, Krakoff J, Votruba SB, Piaggi P. Reduced metabolic efficiency in sedentary eucaloric conditions predicts greater weight regain in adults with obesity following sustained weight loss. Int J Obes (Lond). 2021 Apr;45(4):840-849. doi: 10.1038/s41366-021-00748-y. Epub 2021 Jan 21.

    PubMed 33479452

  • Reinhardt M, Schlogl M, Bonfiglio S, Votruba SB, Krakoff J, Thearle MS. Lower core body temperature and greater body fat are components of a human thrifty phenotype. Int J Obes (Lond). 2016 May;40(5):754-60. doi: 10.1038/ijo.2015.229. Epub 2015 Oct 26.

    PubMed 26499440

  • Schlogl M, Piaggi P, Pannacciuli N, Bonfiglio SM, Krakoff J, Thearle MS. Energy Expenditure Responses to Fasting and Overfeeding Identify Phenotypes Associated With Weight Change. Diabetes. 2015 Nov;64(11):3680-9. doi: 10.2337/db15-0382. Epub 2015 Jul 16.

    PubMed 26185280

  • Maushart CI, Senn JR, Loeliger RC, Kraenzlin ME, Muller J, Becker AS, Balaz M, Wolfrum C, Burger IA, Betz MJ. Free Thyroxine Levels are Associated with Cold Induced Thermogenesis in Healthy Euthyroid Individuals. Front Endocrinol (Lausanne). 2021 Jun 14;12:666595. doi: 10.3389/fendo.2021.666595. eCollection 2021.

    PubMed 34194392

  • Redman LM, Smith SR, Burton JH, Martin CK, Il'yasova D, Ravussin E. Metabolic Slowing and Reduced Oxidative Damage with Sustained Caloric Restriction Support the Rate of Living and Oxidative Damage Theories of Aging. Cell Metab. 2018 Apr 3;27(4):805-815.e4. doi: 10.1016/j.cmet.2018.02.019. Epub 2018 Mar 22.

    PubMed 29576535

  • Oeckl J, Janovska P, Adamcova K, Bardova K, Brunner S, Dieckmann S, Ecker J, Fromme T, Funda J, Gantert T, Giansanti P, Hidrobo MS, Kuda O, Kuster B, Li Y, Pohl R, Schmitt S, Schweizer S, Zischka H, Zouhar P, Kopecky J, Klingenspor M. Loss of UCP1 function augments recruitment of futile lipid cycling for thermogenesis in murine brown fat. Mol Metab. 2022 Jul;61:101499. doi: 10.1016/j.molmet.2022.101499. Epub 2022 Apr 22.

    PubMed 35470094

  • Pontzer H, Yamada Y, Sagayama H, Ainslie PN, Andersen LF, Anderson LJ, Arab L, Baddou I, Bedu-Addo K, Blaak EE, Blanc S, Bonomi AG, Bouten CVC, Bovet P, Buchowski MS, Butte NF, Camps SG, Close GL, Cooper JA, Cooper R, Das SK, Dugas LR, Ekelund U, Entringer S, Forrester T, Fudge BW, Goris AH, Gurven M, Hambly C, El Hamdouchi A, Hoos MB, Hu S, Joonas N, Joosen AM, Katzmarzyk P, Kempen KP, Kimura M, Kraus WE, Kushner RF, Lambert EV, Leonard WR, Lessan N, Martin C, Medin AC, Meijer EP, Morehen JC, Morton JP, Neuhouser ML, Nicklas TA, Ojiambo RM, Pietilainen KH, Pitsiladis YP, Plange-Rhule J, Plasqui G, Prentice RL, Rabinovich RA, Racette SB, Raichlen DA, Ravussin E, Reynolds RM, Roberts SB, Schuit AJ, Sjodin AM, Stice E, Urlacher SS, Valenti G, Van Etten LM, Van Mil EA, Wells JCK, Wilson G, Wood BM, Yanovski J, Yoshida T, Zhang X, Murphy-Alford AJ, Loechl C, Luke AH, Rood J, Schoeller DA, Westerterp KR, Wong WW, Speakman JR; IAEA DLW Database Consortium. Daily energy expenditure through the human life course. Science. 2021 Aug 13;373(6556):808-812. doi: 10.1126/science.abe5017.

    PubMed 34385400

Questions about this trial

What is this clinical trial studying?

A study testing mixed meal test in people with Fasting, run by ETH Zurich at 1 site in Switzerland.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 2 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: looking for participants now, as of the sponsor's last update on 30 May 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in Switzerland. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

Contact Matthias Betz (0041 61 265 2525, matthias.betz@usb.ch), or a site near the patient. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

change of energy expenditure (EE) determined by indirect calorimetry (kcal per 24h) (time frame: 60 minutes after ingestion of test meal). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06134258, which also lists 7 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 30 May 2025.

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