I gained 13.6 pounds of muscle in four months. Probably not.

I got my fifth DEXA scan yesterday. The summary popped up on the iPad before I’d even gotten off the table. Lean mass: 252.6 lbs. Up from 239.0 in January. +13.6 pounds of lean tissue in four months.

I lifted five days a week. I ate in a surplus. I’m 35 and a half, several years into serious training. That number is not how muscle accrual is supposed to work.

The DEXA report calls it “Lean Mass.” On the same page, in light grey type, it explains what’s in that bucket: “Muscle Mass, Organs, Blood and Stomach Contents.” Nothing in the report tells me how those four split. The number I actually want — pounds of contractile skeletal muscle — isn’t on the page.

Glycogen is the big one. Trained skeletal muscle stores roughly 15–18g of glycogen per kg, and each gram of glycogen carries about three grams of water. For somebody my size, fully topped off, that’s plausibly 4–6 lbs of glycogen and bound water sitting inside muscle tissue. DEXA reads all of it as lean mass.

The January scan I went into fasted, after a low-carb day. The May scan I went into on the back of a normal training week, with my usual pre-workout carbs on board. If muscle glycogen was meaningfully more depleted in January than in May — and it almost certainly was — four to five pounds of the “gain” is plumbing.

Then there’s measurement noise. DEXA is good but not perfect. Reproducibility studies on the Lunar Prodigy put intra-machine variance for lean mass at something like ±1–2 lbs even on back-to-back scans, more across months once positioning, hydration, and machine drift stack up.

So out of the 13.6 lbs:

• ~4–5 lbs glycogen + bound water, optimistic
• ~1–2 lbs measurement noise
• ~1 lb organ-mass shifts at this size (gut content, training-driven blood volume)
• That leaves maybe 5–7 lbs of new muscle, best case

Five to seven pounds of real muscle in four months at 35 is still aggressive — closer to what the literature calls possible for younger, less-trained lifters. My honest guess is 2–4 lbs. Which is good. Two to four pounds of actual muscle in four months is a solid bulk. But “+13.6” is the number on the report, and it’s the one I almost posted about.

The five-scan trend tells the better story than any single scan:

Two ~14-lb jumps; two boring middle scans. The boring ones — +5.2 over nine months and +3.2 over three — match what the literature predicts and what my lifting numbers actually corroborate. The jumps line up with scans I walked into hydrated, fed, and post-training-week. The pattern isn’t “I gain ten pounds of muscle in a quarter and then plateau.” It’s “I gain a couple pounds of muscle, quarter over quarter, and the rest is signal noise the DEXA dutifully reports as muscle.”

I start a twelve-week cut tomorrow. The next scan, fasted, on a low-carb day, will tell me what’s actually structural. If lean mass drops 6–8 lbs while body fat drops 15, that’s mostly the glycogen-and-water tax coming due, and what’s left is what I actually built. If it drops 12+, the +13.6 was almost entirely smoke.

I don’t know which it’ll be yet.