Reducing muscle mass lowers the number of calories the body burns at rest.

See the scientific wording

Loss of muscle mass decreases basal metabolic rate in humans.

Supporting

Moderate

2 studies

Correlational — new studies may shift this

Observational

2 moderate-quality studies link this claim to the outcome, but causation is not established.

What the research says

2 studies reviewed

Supporting (2)

Moderate

The age-related decline in resting energy expenditure in humans is due to the loss of fat-free mass and to alterations in its metabolically active components.
Cross-Sectional StudyHuman2003
This study shows that when people lose muscle, their body burns fewer calories at rest, which supports the idea that muscle loss lowers metabolism.
Contribution of individual organ mass loss to weight loss-associated decline in resting energy expenditure.
Cohort StudyHuman2009
This study shows that when people lose weight, they lose some muscle, and that makes their body burn fewer calories at rest - exactly what the claim says.

Contradicting (0)

None

No contradicting studies found yet

That doesn't mean it's settled — it just means no study has tested the opposite.

Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.

Scores reflect study quality, not just count.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 2 supporting studies

About Fit Body Science

How Fit Body Science checks a claim

1
We isolate the claim
Health advice from videos, articles and studies is broken down into single, testable claims.
2
We find the research
Each claim is matched against peer-reviewed studies, with every source cited by DOI.
3
We grade the evidence
Studies are scored on methodology, statistical rigor, transparency and publication quality.

See how the 0–100 score is calculated

What is Fit Body Science?

The fitness and health internet is full of confident claims. We check them against real research.

Every claim on this site is traced back to peer-reviewed studies, scored on methodology and reporting quality, and given a verdict you can audit yourself — sources, DOIs and all.

Full evidence breakdown and mechanism chains
Ask our AI anything about a claim or its studies
Get notified when new research changes a verdict