Leucine and HMB for muscle growth in young men lifting weights
What it found
Adding leucine to a whey protein shake built just as much muscle and strength as adding HMB, a compound made from leucine.
This was found in 26 young men who lifted weights for 12 weeks.
What they found
Studies in people
Muscle size gains
Both groups gained about the same amount of lean body mass over 12 weeks. The HMB group gained 2.3 kg on average and the leucine group gained 2.6 kg. Ultrasound scans showed similar increases in thigh muscle thickness and area in both groups.
Strength improvements
The heaviest weight the men could lift went up equally well in both groups. Total strength across three lifts rose by 70 kg in the HMB group and 80 kg in the leucine group, which the authors say is about the same.
Hormone levels
Blood tests checked hormones like testosterone, cortisol and growth hormone at several points. Neither supplement changed these hormone levels differently from the other during any phase of the training.
Power output changes
Cycling power tests improved similarly in both groups after 12 weeks. During a very intense training phase, peak cycling power actually dropped more in the HMB group than in the leucine group.
What the authors conclude
- They conclude that adding HMB to whey protein does not build more muscle or strength than adding leucine to whey protein in young men who lift weights.
- Their results contradict earlier studies that reported unusually large muscle gains from HMB supplements.
- They suggest that people who lift weights do not need to choose HMB over leucine when using a whey protein shake.
How it was done
Some earlier reports claimed that HMB, a substance the body makes from leucine, builds far more muscle than leucine itself. The authors wanted to test this by comparing the two directly when added to whey protein.
Twenty-six young men who already lifted weights twice a week took part. For 12 weeks they followed a supervised weightlifting program and drank a whey protein shake twice a day. Half got 1.5 g of HMB in each shake and half got 1.5 g of leucine instead.
What it can’t tell you
- This trial only looked at young men who were already lifting weights regularly. It cannot show what would happen in women, older adults or people new to exercise.
- Everyone in the trial also took whey protein. The study cannot show how leucine or HMB might work if taken without any extra protein.
Who paid
- Authors work at
- McMaster University, CANADA; Federal University of Santa Catarina, BRAZIL
The paper
- Title
- Equivalent Hypertrophy and Strength Gains in β-Hydroxy-β-Methylbutyrate- or Leucine-supplemented Men
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Jakubowski JS, Wong EPT, Nunes EA, et al (2019). Equivalent Hypertrophy and Strength Gains in β-Hydroxy-β-Methylbutyrate- or Leucine-supplemented Men. Medicine and science in sports and exercise. doi:10.1249/MSS.0000000000001752Free full textPubMed 30113522DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error