L-Leucine
120 mg publishedThe formula’s primary BCAA and a key trigger associated with muscle protein synthesis.
Who it’s for · 01
When appetite drops, protein still has a job.
Appetite-reducing weight-loss medications make it easy to under-eat protein. Muscle notices before the scale does. This page covers where an amino acid capsule fits, where it doesn’t, and what the evidence actually shows.
The honest part
No published trial has tested amino acid or protein supplements in people taking GLP-1 medications with a muscle outcome (checked against PubMed on 2026-09-15). What exists is evidence from diet-only weight loss: higher protein intake helps keep lean mass while eating less. POWER9® is a dietary supplement, not part of a prescription plan. Keep your prescriber in the loop.
Where it fits
Moments this page is written for.
Small mealsWhen a full plate is off the table and protein has to fit in less.
Days food feels like a choreNine amino acids at close to zero calories, no shake to finish.
Keeping training goingResistance work is the other half of holding on to muscle.
What the research covers
The studies closest to your situation.
Graded by strength of human evidence, with the population and dose each study used. Compare the dose studied with the amount on the POWER9® label before deciding what a finding means for you.
- Strong
Higher-protein diet (comparator; indirect evidence for the GLP-1 segment) Lean-mass preservation during caloric restriction
Meta-analysis of 24 RCTs (n=1063) shows energy-restricted high-protein diets mitigate fat-free-mass loss (+0.43 kg) and REE decline versus standard protein; a meta-analysis of 20 RCTs in adults 50+ finds more lean-mass retention with higher protein; a 4-week RCT with 2.4 vs 1.2 g/kg/day during a 40% deficit plus training produced +1.2 vs +0.1 kg lean mass. Consistent, but none of these trials involved GLP-1 drugs.
Adults and older adults undergoing diet-induced weight loss (no GLP-1 therapy) · Dose: >=25% energy from protein or >=1.0 g/kg/day; up to 2.4 g/kg/day with intense training · meta-analysis, 2012, PMID 23097268 - Promising
Whey protein + leucine + vitamin D supplement Muscle preservation during intentional weight loss in obese older adults
Double-blind RCT (n=80, 13 weeks, -600 kcal/day diet plus resistance training): appendicular muscle mass changed +0.4 kg with the supplement vs -0.5 kg with isocaloric control, with equal weight and fat loss; strength and function did not differ. Single well-run trial; diet-induced, not drug-induced, weight loss.
Obese older adults (mean 63 y, BMI 33) on a hypocaloric diet with resistance training · Dose: 21 g protein per serving, 10 servings/week (leucine- and vitamin D-enriched) · RCT, 2015, PMID 25646324 - Slight
Essential amino acid blend (EAA) + whey meal replacement Lean-mass preservation during caloric restriction in obese elderly
Small RCT (n=12, 8 weeks, 7% weight loss): the EAA/whey meal replacement did not significantly preserve lean tissue versus a competitor product but produced greater fat loss and higher acute MPS. Tiny sample; mixed result.
Elderly obese adults on an 1200 kcal/day diet · Dose: 800 kcal/day EAA/whey meal replacements (EAA dose not in abstract) · RCT, 2012, PMID 23231757 - No evidence or conflicting
Essential amino acids / protein supplementation Lean-mass preservation during GLP-1 medication
No randomized trial of EAA, leucine, or protein supplementation in GLP-1-treated patients with a lean-mass outcome was found on PubMed as of 2026-09-15. What exists: a 2026 meta-analysis of 7 RCTs (n=821) quantifying lean-mass loss on obesity-dose GLP-1 medication (absolute -1.74 kg; one drug -5.44 kg; lean mass as a proportion of weight actually rises), a 2024 review of mitigation strategies, and a 2025 narrative review recommending protein 1.2-2.0 g/kg/day, creatine and HMB by extrapolation from non-GLP-1 weight-loss trials. Untested, not disproven.
Adults with obesity on GLP-1 medication · Dose: None tested directly; reviews suggest 1.2-2.0 g protein/kg/day by extrapolation · meta-analysis, 2026, PMID 42321502
Inside the formula for this
The amino acids doing the work.
Published amounts per serving. The full nine-part formula lives on the POWER9® page.
L-Valine
60 mg publishedA BCAA used by the body in protein synthesis and muscle maintenance.
L-Isoleucine
60 mg publishedA BCAA commonly associated with energy and exercise recovery.
L-Lysine
50 mg publishedAn essential amino acid involved in protein synthesis and other body functions.
The leucine-led BCAAs are the amino acids most associated with keeping muscle protein synthesis signaled while intake goes down. Lysine is an essential amino acid the body uses in protein synthesis. Food-first protein still sets the floor.
Straight answers
Questions people in this situation ask.
01Does POWER9® prevent muscle loss on a GLP-1 medication?+
No supplement can claim that. No trial has tested amino acid supplements in people taking these medications. Diet-only weight-loss studies show higher protein intake helps keep lean mass. Ask your prescriber for your protein target.
02How much protein do I need while eating less?+
Reviews of weight-loss trials commonly cite 1.2 to 2.0 grams per kilogram of body weight per day, from food first. Your clinician sets your number based on your plan and health.
03Can capsules replace protein foods?+
No. POWER9® adds nine amino acids at close to zero calories. It does not replace complete protein from food.
Related reading
From the journal.
Educational reading, not medical advice.