Otherindependent cross-checkabstract checked I-FAST-103 standard review
Normal hormone values during a three-day fast
Reference intervals for glucose, beta-cell polypeptides, and counterregulatory factors during prolonged fasting.
Overview
Højlund K et al.. Am J Physiol Endocrinol Metab 2001 · PMID 11120658 · DOI 10.1152/ajpendo.2001.280.1.E50
In 33 healthy adults fasting 72 hours, glucose and insulin went down while stress hormones went up.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Define normal values during the 72-hour fast test.
- How was the study done?
Repeated blood sampling during a 72-h fast.
- How many people, animals or samples were studied?
33 healthy Danish adults.
- What was actually found?
Glucose, insulin and C-peptide decreased; glucagon, FFA, cortisol, catecholamines increased.
- How large was the observed effect?
P<0.001 for decreases (values not in abstract).
- What do the results mean in everyday life?
When healthy people fast, insulin and blood sugar go down, not up.
- What are the study's limitations?
Values not available from abstract.
- What does it say about Elawady's specific claim?
Insulin falls but is measured throughout; blood sugar falls in healthy fasting.
- Do the results apply to Germany and Europe?
Applies; same physiology.
- What can explicitly not be concluded from this study?
Whether insulin ever reaches undetectable levels in individuals.
Scientific in-depth review
1. Full reference
- Authors
- Højlund K et al.
- Journal
- Am J Physiol Endocrinol Metab
- Year
- 2001
- Identifier
- PMID 11120658 DOI 10.1152/ajpendo.2001.280.1.E50
- Verification
- verified – PubMed efetch 2026-10-26; Crossref update-to/updated-by check
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
What are normal glucose, insulin, C-peptide, proinsulin and counter-regulatory hormone levels during a 72-h fast?
3. Study design and population
- Study design
- Other – Prospective physiological study (72-h fast) to establish reference intervals
- Population
Healthy adults
- Country
Denmark
- Period
not stated in abstract
- Sample size
33 (16 men, 17 women)
- Inclusion and exclusion criteria
not stated in abstract
4. Methods and endpoints
- Exposure / intervention
72-h fast
- Comparator
Baseline (start of fast)
- Endpoints
Glucose, insulin, C-peptide, proinsulin, glucagon, FFA, catecholamines, cortisol, growth hormone
- Statistical methods
Repeated measures; reference intervals
5. Actual results
- Results
Glucose, insulin, C-peptide and proinsulin decreased (P<0.001); glucagon and FFA increased linearly; adrenaline, noradrenaline and cortisol rose with circadian rhythm; higher BMI gave higher insulin and C-peptide during the fast (P<0.05).
- Absolute risks
not reported
- Authors' conclusion
Reference intervals for glucoregulatory factors during a 72-h fast; diminished beta-cell response with increased counter-regulatory hormones.
6. Strengths
- Healthy volunteers of both sexes
- Standardised 72-h fast used clinically
7. Weaknesses
- Absolute values not in abstract (full text not accessed)
- Small sample
8. Risk of bias
- Orienting tool
- none applicable
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Descriptive physiology; risk of bias low for the question asked.
9. Assessment of the statistical interpretation
Insulin and C-peptide decrease; reference intervals for the 72-h fast are reported (values not in abstract, so whether any individual reached undetectable levels cannot be judged); glucose falls rather than rises in healthy fasting.
10. Relevance to the specific claim
Confirms the correct part (insulin falls with fasting) and shows glucose falls in healthy fasting, against both 'zero insulin' and 'rising glucose' as normal.
11. Independent contrary findings
12. Transferability to Germany and Europe
Universal biology; applies in Europe and Egypt.
13. Overall methodological judgement
Supports the kernel 'insulin falls'; provides no support for 'zero'.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | low |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
15. Linked fact checks
- Fasting brings gut hormones, above all insulin, to zero ('your fasting insulin equals zero'). – Studies with mixed or unclear results