Lifting light or heavy weights to exhaustion for 12 weeks didn’t change body fat or muscle mass in women who had never lifted before.

Scientific Claim

Twelve weeks of resistance training to failure at either low (30% 1RM) or high (80% 1RM) loads does not significantly alter bone- and fat-free mass or percent body fat in untrained women.

Original Statement

“There were no significant changes in BFFM (p = 0.241) or %BF (p = 0.740) for either group.”

From study:Low-Load vs. High-Load Resistance Training to Failure on One Repetition Maximum Strength and Body Composition in Untrained Women.

Evidence Quality Assessment

Claim Status

overstated

Study Design Support

Design cannot support claim

Appropriate Language Strength

association

Can only show association/correlation

Assessment Explanation

The claim implies a universal absence of effect, but the study only observed no significant changes in a small group without confirmed randomization. The verb 'does not alter' overstates the evidence.

More Accurate Statement

“In untrained women, 12 weeks of resistance training to failure at either 30% or 80% 1RM is associated with no significant changes in bone- and fat-free mass or percent body fat, though the lack of randomization limits generalizability.”

Evidence from Studies

Supporting (1)

Low-Load vs. High-Load Resistance Training to Failure on One Repetition Maximum Strength and Body Composition in Untrained Women.

Randomized Controlled Trial

Human

2019 Jul

The study found that even though women got stronger after 12 weeks of lifting weights, their muscle and fat levels didn’t change—no matter if they lifted light or heavy weights, as long as they pushed to exhaustion.

Contradicting (0)

No contradicting evidence found

Source Study

Low-Load vs. High-Load Resistance Training to Failure on One Repetition Maximum Strength and Body Composition in Untrained Women.

Score: 38

DOI: 10.1519/JSC.0000000000003194

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