Tier 4 — mechanistic

Metabolic impact of dietary glycine supplementation in individuals with severe obesity

Tan HC, Hsu JW, Tai ES, Chacko S, Wu V, Yen PM, Kovalik JP, Jahoor F
Scientific reports 2025 15(1):36433

Bibliography

PubMed
PMID 41107432
PubMed Central
PMC12534614
DOI
10.1038/s41598-025-20511-x
Trial registry
View on ClinicalTrials.gov Registered trial — results not yet published in a peer-reviewed journal.
Funding
Khoo Mentored Research Grant, Duke-NUS KMRA 2020/0013.
Competing interests
The authors declared no competing interests.

Study snapshot

DesignExploratory human intervention
ModelAdult humans
Sample19 adults with severe obesity; 17 completed mixed-meal tests
InterventionOral glycine 100 mg/kg/day; no placebo control
Duration2 weeks
EndpointsPlasma glycine; Acylglycine excretion; Triglycerides and liver enzymes; Glutathione; Insulin sensitivity and homocysteine

What the study showed, in plain terms

In severe obesity, glycine supplementation raised circulating glycine and altered selected metabolic markers. The uncontrolled pilot found no improvement in insulin sensitivity or glutathione and did not directly measure reversal of liver disease.

Key findings

  • Triglycerides and aminotransferases decreased; body weight did not change.
  • HbA1c, fasting glucose, insulin-sensitivity indices and mixed-meal responses did not significantly improve.
  • Homocysteine increased during treatment; the long-term significance was not tested.

What this study can and cannot tell us

No placebo group, small sample and two-week exposure prevent causal conclusions.

A liver-related surrogate index is not imaging or histological proof of MASLD treatment.

Related papers in the corpus

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The metabolic response to ingested glycine
Gannon MC et al. · The American journal of clinical nutrition · 2002
Tier 2
Effect of glycine on insulin secretion and action in healthy first-degree relatives of type 2 diabetes mellitus patients
González-Ortiz M et al. · Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme · 2001
Tier 2
Glycine treatment decreases proinflammatory cytokines and increases interferon-gamma in patients with type 2 diabetes
Cruz M et al. · Journal of endocrinological investigation · 2008
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Oral supplementation with glycine reduces oxidative stress in patients with metabolic syndrome, improving their systolic blood pressure
Díaz-Flores M et al. · Canadian journal of physiology and pharmacology · 2013
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De Novo Glycine Synthesis Is Reduced in Adults With Morbid Obesity and Increases Following Bariatric Surgery
Tan HC et al. · Frontiers in endocrinology · 2022
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Low serum glycine strengthens the association between branched-chain amino acids and impaired insulin sensitivity assessed before and after weight loss in a population with pre-diabetes: The PREVIEW_NZ cohort
Lim JJ et al. · Clinical nutrition (Edinburgh, Scotland) · 2024

Editorial review

Reviewed by the Biohack Blueprint research team

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction