WHAT THIS STUDY IS A landmark Phase III randomized controlled trial published in the New England Journal of Medicine, examining whether tesamorelin — a growth hormone-releasing factor analog — could reduce visceral fat accumulation. This trial, alongside a companion Phase III study, formed the clinical evidence base that led the FDA to approve tesamorelin in 2010 — making it the only growth hormone-releasing hormone (GHRH) analog with an FDA-approved indication for visceral fat reduction.
THE CORE FINDING Tesamorelin selectively reduces visceral fat — the metabolically dangerous fat that surrounds internal organs — without significantly affecting subcutaneous fat, limb fat, or overall body weight. This selectivity is what distinguishes it from generalized weight-loss approaches: it targets the specific fat depot most strongly linked to cardiovascular risk, insulin resistance, and metabolic dysfunction.
THE TRIAL 412 patients with documented abdominal fat accumulation were randomly assigned to receive a daily subcutaneous injection of either 2mg of tesamorelin or placebo for 26 weeks. Visceral adipose tissue was measured directly via CT scan — not estimated from waist circumference or body weight, but actually imaged.
KEY DATA POINTS
Visceral fat decreased by 15.2% in the tesamorelin group, compared to a 5.0% increase in the placebo group (p < 0.001)
Triglycerides dropped by 50 mg/dL in the tesamorelin group, vs. an increase of 9 mg/dL in placebo
The total cholesterol-to-HDL ratio improved significantly in the tesamorelin group
IGF-1 levels — a direct marker of growth hormone activity — increased by 81% in the tesamorelin group, compared to a 5% decrease in placebo
A pooled analysis of this trial and a second Phase III study (816 patients combined) found 69% of tesamorelin-treated patients achieved a clinically meaningful visceral fat reduction of 8% or greater, compared to 33% on placebo
THE FDA APPROVAL This trial — together with a second pivotal Phase III study — formed the basis for the FDA's 2010 approval of tesamorelin (brand name Egrifta) for reducing excess abdominal fat. It remains the only GHRH analog with this FDA-approved indication, distinguishing it from other peptides in this class that operate in a less-regulated, off-label space.
WHY THIS MATTERS Most peptides marketed for "fat loss" rely on indirect evidence, animal studies, or anecdotal reports. Tesamorelin's effect on visceral fat was measured directly via CT imaging in a large, randomized, placebo-controlled trial — and the result was strong enough to clear FDA review. For a compound class where regulatory clarity is rare, tesamorelin stands out as the exception: a peptide with a defined mechanism, a measurable outcome, and regulatory approval behind it.
Falutz et al. | New England Journal of Medicine | Vol. 357, No. 23 | December 2007
Read the full journal here: https://pubmed.ncbi.nlm.nih.gov/18057338/