One Year Ago Today I Weighed 308: The Muscle-Loss Frame Just Got Rewritten

11:58 ET. Side door of the kitchen, second cup of coffee, the InBody printout from the 05-19 reweigh next to the phone.

TL;DR

• May 21 2025: 308 lbs on a kitchen scale at this same address. May 21 2026: 196.4 lbs, 14.1% body fat, fat-free mass 168.7 lbs. Twelve months. Retatrutide (GLP-3 triple agonist) plus four levers — protein floor, resistance training, sleep, and an over-40 calorie-floor that I was citing too aggressively a year ago.
• The Cell Reports Medicine 2026 paper and the European Congress on Obesity Istanbul readout (May 12-15) just published a Vienna obesity-clinic cohort, n=486, mean age 49.9 years, showing that **80-85% of GLP-1 weight loss is fat mass with relative muscle preservation** when the patient is in care.
• This walks back the "20% of weight loss is lean mass" frame that became internet conventional wisdom in 2024-2025 — the frame I was citing across multiple pieces on this site as recently as April. The math just changed.
• What still applies: the muscle preservation in the new data is *relative* (proportion-of-loss), not *absolute* (zero lean-mass change). Resistance training and a 1.2-1.6 g/kg protein floor are still the two levers that move the absolute number from "preserved on paper" to "preserved on the InBody."
• The honest-revision call: every blog with a GLP-1-muscle-loss panic piece from 2025 is stale this week. Read this one twice if you started a GLP-1 because of the muscle-loss fear and you have been undereating protein since.

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The number on the scale on May 21 2025

I weighed 308 lbs.

I know the date because I wrote it down in the same notebook where I had been writing down every other failed diet attempt since 2018. Most of those pages have a starting weight and no end weight. This one has both.

A year later, the entry from this morning's reweigh: 196.4 lbs, 14.1% body fat, fat-free mass 168.7 lbs, visceral fat down from a level that would not fit on the InBody chart to a number that finally does.

The drug is retatrutide. The gym-bro press calls it GLP-3 because it stacks GLP-1, GIP, and glucagon receptor agonism on a single molecule. The TRIUMPH-1 Phase 3 readout dropped on May 4 of this year. I wrote about it the same morning, two cups of coffee in, looking at the same InBody slip from a different week.

This is not the TRIUMPH-1 piece. This is the piece I owed myself a year out — the audit of every claim I made along the way, including the ones the science walked back this month.

The 2025 frame: "GLP-1s eat your muscle"

The line entered the wellness internet in waves through 2024 and crystallized into conventional wisdom by spring 2025.

The most cited number was that 20% of weight lost on a GLP-1 is lean mass. It came out of an early sub-analysis of the STEP-1 data and got amplified by every podcast that wanted a hook against the drugs. Strength coaches built entire content schedules around it. I bought the framing — and I quoted the framing — when I started writing about my own arc in summer 2025.

I was not wrong to take it seriously. The mechanism is real: any rapid energy deficit will pull some mass from the lean compartment, and elderly or sedentary or under-protein patients have a much harder ride than fit ones.

But "20% of every pound on a GLP-1 is muscle" is a different claim from "the average patient on these drugs is losing muscle at a higher rate than other rapid-loss protocols." The second claim is what the new data tests. And the second claim does not hold up.

What the May 2026 data actually says

Two papers and a press wave broke this month.

The first is in Cell Reports Medicine — Locatelli et al., 2026 ("Weight loss with GLP-1 medicines does not result in a disproportionate loss of muscle mass or function in obese mice and humans"). The paper combines a mouse model with a human re-analysis and concludes that lean-mass loss on semaglutide tracks what you would expect from any equivalent-magnitude weight loss — not more.

The second is the ECO Istanbul readout (European Congress on Obesity, May 12-15, 2026). Frohner, Jürets, and Itariu of the Metabolism Center N°12 Antonigasse in Vienna ran a retrospective cohort of 486 adult patients with obesity — mean BMI 37.68, mean age 49.9 years (which is the patient cohort I write for almost exclusively), 82% female, treated with liraglutide (8%), semaglutide (82%), or tirzepatide (8%). They used bioelectrical-impedance analysis to track skeletal muscle mass and fat mass during therapy.

The headline finding: 80-85% of total weight loss was fat mass, and relative muscle mass was preserved.

The American Diabetes Association press release on May 13 led with the same number under the headline "New GLP-1 Therapies Enhance Quality of Weight Loss by Improving Muscle Preservation." News-Medical, MedicalXpress, ukactive, and the May 2026 Aimelet review in Diabetes, Obesity and Metabolism all carried the same shape of story this week.

The honest read: when a 49.9-year-old patient with a BMI of 37.68 loses 25-30 lbs on a GLP-1 in a real-world clinic, the bioimpedance-measured fat loss is the dominant signal and skeletal muscle is largely riding along. That is genuinely different from the 2024 framing.

What the data does *not* say

This is the part the headlines will not write.

"Relative muscle mass preserved" is a ratio. It is the proportion of body mass that is muscle. If you lose 30 lbs of total weight and 25 of those are fat and 5 are lean, the relative muscle-mass percentage of your body goes up — because fat fell faster. That is what 80-85% fat-mass loss means. It does not mean the lean number on the InBody did not move.

The May 2026 Aimelet review in Diabetes, Obesity and Metabolism is the clean read on this point. It notes that pharmacological mono-therapy without resistance training and adequate protein still produces absolute lean-mass changes — and that those changes matter for the over-40 patient whose baseline sarcopenia risk is already elevated.

Translation for the 49-year-old reader: the panic was overstated. The discipline was not.

What I did in the twelve months

I will give you the version that fits in one screen.

Lever 1 — Protein floor. I did not chase the 1g-per-pound-of-bodyweight target that gets quoted in the gym-bro press, because at 308 lbs that math is nonsense and at 196 it is still aggressive. I held a 1.2 to 1.6 g per kg of target-bodyweight floor — roughly 105 to 145 grams of protein daily depending on the week — distributed across three to four meals, with at least 2.5g of leucine per meal. The 2.5g leucine number is from the Schoenfeld and Aragon work on the muscle-protein synthesis threshold per meal, and it is the number that matters more than the daily total for the over-40 patient.

Lever 2 — Resistance training. Three lifts a week, compound-first. Not the YouTube hypertrophy split. The Frontiers Clinical Diabetes 2025 paper "GLP-1 agonists and exercise: the future of lifestyle prioritization" makes the cleanest version of this argument — that individuals who continue to exercise during pharmacologic treatment maintain greater fat loss and preserve lean mass after stopping medication than those using medication alone. I am writing this piece while still on the molecule. The lifting is the asset that pays out the year I taper.

Lever 3 — Sleep. The lever nobody wants to hear about. I held seven hours of sleep on a security-officer schedule with a teenager in the house, and on the weeks I did not, the InBody printout reflected it.

Lever 4 — A floor on the calorie deficit. Not a ceiling. A floor. The fastest weeks were not the strongest weeks. The over-40 patient on a triple-agonist already has a 25%+ caloric reduction handed to them by the drug — driving the deficit further with a manual restriction on top of that is how you end up in the absolute-lean-mass-loss bucket the Vienna paper says is preventable.

What this means if you started this year

If you started semaglutide or tirzepatide in the last twelve months because the weight-loss number was undeniable but you were terrified of the muscle-loss frame — read the Cell Reports Medicine paper and the ECO Istanbul press wave this week. The framing has been walked back. The drugs work. The muscle compartment in the Vienna cohort came through the loss in better shape than the 2024 internet predicted.

If you started a GLP-1 because of the muscle-loss fear and you have been underconsuming protein to "match" what you thought the drug was doing to your lean mass — that is the readership I am most worried about this week. Get your protein floor back up. The fear was based on a frame that has not survived May 2026.

If you have been resistant-training and protein-feeding and on the molecule the whole way — the new data is a confirmation, not a permission slip. The reason your InBody numbers look the way they do is the lifting and the protein. The drug was the accelerant. The discipline was the asset.

If you have been on the drug without resistance training because you assumed the molecule would protect the muscle on its own — the Vienna paper does not actually say that. It says the relative proportion of muscle on your body comes through preserved. The absolute number on the lean-mass row of the InBody still rewards lifting. There is no version of this story where the over-40 patient skips the strength work.

What I am writing about the rest of this week

The Memorial Day taper week starts Friday. I have one more piece coming on the adherence-cohort data from the LinkedIn readers who stayed nine minutes on the AI-coach-vs-personal-trainer piece on Tuesday — knowledge-worker over-40s with a structural adherence problem that the AI-coach format actually solves.

The Father's Day cluster opens next week. The 47-year-old reader with a dad who has not had a physical in three years is the cohort that piece is for.

And the orforglipron readout is still untapped — the once-daily oral GLP-1 that the injection-averse over-40 cohort has been waiting on for two years. That piece is coming.

For now: it has been twelve months. I weighed 308. I weigh 196. The science is closer to what I have been seeing on my own InBody than it was a year ago. The fear was overstated. The discipline was not.

Eat your protein. Pick the bar back up. Get seven hours of sleep. Read the May 2026 papers if you have been carrying the 2024 framing around as gospel.

I will be back tomorrow morning at 06:00 with the adherence-cohort piece.

— Jake

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Sources

• Locatelli, J. et al. (2026). *Weight loss with GLP-1 medicines does not result in a disproportionate loss of muscle mass or function in obese mice and humans.* Cell Reports Medicine. https://www.cell.com/cell-reports-medicine/fulltext/S2666-3791(26)00082-0
• Frohner, E. I., Jürets, A., Itariu, B. K. (2026). ECO Istanbul May 12-15 2026: Vienna Metabolism Center N°12 Antonigasse retrospective cohort n=486. https://www.news-medical.net/news/20260513/GLP-1-obesity-drugs-mainly-reduce-fat-while-preserving-muscle-mass.aspx
• American Diabetes Association press release (2026-05-13). *New GLP-1 Therapies Enhance Quality of Weight Loss by Improving Muscle Preservation.* https://diabetes.org/newsroom/press-releases/new-glp-1-therapies-enhance-quality-weight-loss-improving-muscle-0
• Aimelet et al. (2026). *Pharmacological intervention: Challenges and promising outcomes for fat loss and preservation of lean body mass in the treatment of overweight and type 2 diabetes.* Diabetes, Obesity and Metabolism. https://dom-pubs.onlinelibrary.wiley.com/doi/full/10.1111/dom.70229
• ukactive resource brief — *GLP-1 medications and muscle mass preservation.* https://ukactive.com/resources/glp-1-medications-and-muscle-mass-preservation/
• Frontiers in Clinical Diabetes (2025). *GLP-1 agonists and exercise: the future of lifestyle prioritization.*
• Jastreboff, A. M. et al. (2023). *NEJM* 389:514-526 (retatrutide Phase 2 baseline reference for the 308 → 196 patient on the ride right now).