MK-677 Before and After: The Week-by-Week Timeline From the Human Trials

MK-677 (ibutamoren) is unusual among research compounds in having a two-year, placebo-controlled human trial behind it, plus a run of shorter Merck-era studies from the 1990s that measured GH, IGF-1, body composition, sleep and bone turnover at fixed timepoints. So the "before and after" for this compound does not have to come from forum photographs. It can come from DEXA scans and blood draws on 65 older adults followed for 24 months, and from eight-week studies in obese young men.

This page sets out what those studies say happens week by week on 25 mg daily, what a researcher should record before the first capsule so the "after" is interpretable, how big the real change is against the noise, what reverses on stopping, and where people misread water for muscle. For the pharmacology and the compound's regulatory position, see the Bureau's MK-677 guide.

Where the data come from

The anchor is Nass and colleagues' 2008 trial in the Annals of Internal Medicine: 65 healthy adults aged 60 to 81, randomised to MK-677 25 mg or placebo once daily, with a modified crossover over two years and one-year primary endpoints. Around it sit the earlier Merck studies: a 1996 dose-ranging trial in 32 healthy elderly subjects with 24-hour GH sampling at two and four weeks; a 1998 eight-week trial in 24 obese men aged 18 to 50; a seven-day calorie-restriction crossover in eight young volunteers; a sleep-architecture study in young and older adults; and bone-marker studies out to 18 months. All used 25 mg as the main dose, which is why that number dominates research protocols today.

Two things are missing from this record and matter for reading it. Nobody has published a trial in trained adults under 40, which is most of the people searching this query. And the longest study, the two-year one, was in people over 60 whose GH axis had declined with age. Expect the direction of the effects to transfer; do not assume the size does.

The week-by-week timeline

The line to reread is "no improvement in any strength or function measure". Sixty-five people took the compound for a year, gained a statistically robust kilo of fat-free mass, and were not measurably stronger. The authors say plainly that the study was underpowered for function; the point stands that lean mass on a DEXA and performance in the gym are different measurements.

What to record before the first dose

MK-677 changes water, appetite and glucose before it changes anything you would call a physique, and all three contaminate the usual before-and-after measures. Record the following on the same morning of the week, fasted, before starting.

• Fasting glucose and HbA1c, then insulin if you can get it. Every trial that looked found glucose worse: +1.4 mmol/L fasting at four weeks in the elderly study, an impaired OGTT at two and eight weeks in obese men, +0.3 mmol/L and reduced insulin sensitivity at one year. Without a baseline you cannot see it coming.
• IGF-1. The trial response was 40% to 88% above baseline. A follow-up value only means something against your own starting number, and it tells you whether the compound you bought is doing anything at all.
• Seven-day rolling scale weight. Not a single reading. The first-month gain is dominated by water and food; a rolling average is the only way to separate a trend from Tuesday.
• Waist at the navel and a calf or ankle circumference. The ankle number is for oedema, which the two-year trial lists as a transient effect. If the ankle grows before the arm does, that is water.
• A DEXA or at least bioimpedance, with the caveat that both read intracellular water as lean mass. The trial's +0.8 kg of "body cell mass" was, by its own definition, water inside cells.
• Sleep log or wearable data. The sleep study found stage IV sleep up roughly 50% and REM up more than 20% in young adults at 25 mg, and REM up nearly 50% in older adults, within 7 to 14 days. Sleep is the earliest subjective change and the one most worth tracking against a baseline week.
• Appetite and calorie log, because if intake goes up by a few hundred kilocalories a day for three months, the fat gain in the two-year trial (limb fat +1.1 kg) follows without any help from the compound.
• Photographs, same light, same distance, weekly, understanding that the first month's pictures will show a fuller, softer look from water that later resolves.

Realistic magnitude, and what is noise

The controlled one-year effect on fat-free mass is 1.6 kg relative to placebo (+1.1 versus -0.5). That is real, repeatable across the eight-week and one-year studies, and small. It is also inseparable in the published data from the roughly 0.8 kg of intracellular water and the fact that total weight rose 2.7 kg, of which limb fat accounted for 1.1 kg. Fat did not fall anywhere in the two-year trial; the eight-week study in obese men, where fat loss was the hypothesis, found total and visceral fat unchanged.

The IGF-1 and GH numbers are large and fast, which is what makes the compound feel like it is working. A 24-hour mean GH concentration up 97% and IGF-1 up 88% inside four weeks is an unambiguous pharmacological signal. It is just not the same thing as a body-composition result, and the trials that measured both show the gap.

Noise is bigger than the signal in the first month. A 2 kg scale swing from glycogen, sodium and the compound's own fluid effect is ordinary. DEXA lean-mass readings move by about a kilo with hydration alone. That is why the only fair comparison is the three-month or six-month one, taken at the same hydration and time of day as the baseline.

What reverses on stopping

MK-677 is a ghrelin-receptor agonist that amplifies the body's own GH pulses; it adds no exogenous hormone. GH and IGF-1 return to baseline once the drug clears, and the single-dose GH data (a peak of 55.9 µg/L on day one dropping to 22.6 µg/L after a week) show how quickly the axis adapts even while dosing. The water goes first, usually within a fortnight, taking a kilo or two of scale weight with it. The bone-marker changes are described in the 18-month study as tracking IGF-1, so they are expected to fade as well.

What has not been studied is whether the kilo of fat-free mass persists. No published trial followed participants off drug with a DEXA. The reasonable assumption, given that strength never improved and the tissue gained was partly water, is that most of it does not; the honest statement is that there are no data. The appetite change reverses, which some researchers experience as the opposite problem after months of eating more.

Where people misattribute results

Water as muscle. This is the central error for this compound. The first four weeks produce a fuller look, a heavier scale and a higher DEXA lean number, all of which the trial data attribute substantially to intracellular water and fluid retention. The two-year study's authors called the body-cell-mass increase what it was.

Appetite as anabolism. Eating more builds tissue with or without MK-677. In the one-year data, participants gained more fat than lean, and the placebo group also gained weight. If a researcher's calories went up 20% and their weight went up 3 kg, the compound's contribution is the difference between that and what 20% more food does on its own, which is not much.

Better sleep as "recovery". The sleep effect is genuine and fast, but the trials found no link from it to strength or function. Feeling recovered and being stronger were measured separately, and only one of them changed.

Ignoring the glucose. Fasting glucose rose in every study that measured it. A researcher who feels lethargic or notices increased thirst at week six and blames the appetite, or the extra food, is missing the most consistent finding in the literature. The FDA's stated reason for restricting ibutamoren from compounding is a different one, the potential for congestive heart failure in certain patients, and a 2026 sports-medicine scoping review lists that alongside insulin resistance as the documented risks.

Stacks. MK-677 is often run with an injectable GHRH or GHRP, or with a SARM. The trial numbers on this page apply to 25 mg alone in people who took nothing else. The muscle-growth stack page and the natural GH boosters page cover what the combinations add and what they confuse.

Sourcing and dosing notes

MK-677 is not a peptide; it is an oral small molecule, so there is no reconstitution and no syringe. The trial dose was 25 mg once daily, taken at bedtime in the sleep study, and that is what most research protocols copy. If you are pairing it with an injectable secretagogue such as ipamorelin or tesamorelin, the peptide dosing calculator handles the injectable side, and the ipamorelin guide explains why researchers combine a GHRP with a ghrelin mimetic in the first place.

On sourcing: because MK-677 is sold as a powder or in capsules and liquid suspensions rather than as a lyophilised vial, dose accuracy is a bigger issue than purity, and a vendor that publishes a per-batch certificate showing actual milligram content is worth more than a low price. The Bureau's top-scored source for MK-677 at the time of writing is Pantheon Peptides, which links a lab results page from each listing and ships from the US. Check price at Pantheon Peptides See the Pantheon Peptides review for how the scorecard treats it, and peptide side effects for the glucose and oedema signals to log.

Ibutamoren is a research compound that the FDA has placed on its list of bulk substances that may present significant safety risks. The trial results above come from supervised studies in specific populations; nothing here is medical advice, and the Bureau does not advise anyone on using research compounds.

Frequently Asked Questions

How quickly does MK-677 work?

Hormonally, immediately: peak GH after a single 25 mg dose was 55.9 µg/L against about 9 µg/L on placebo, and IGF-1 rose from 141 to 219 µg/L within 14 days in older adults, reaching 265 µg/L at four weeks. Sleep changes appeared within 7 to 14 days in the sleep study. Body composition is much slower. The eight-week trial found fat-free mass up by DEXA; the one-year trial found +1.1 kg versus -0.5 kg on placebo. Most of the first month's scale gain is water and food.

How much muscle does MK-677 add?

In the only long trial, 65 adults aged 60 to 81 on 25 mg daily gained 1.1 kg of fat-free mass over one year against a 0.5 kg loss on placebo, a 1.6 kg difference. Body cell mass, which is intracellular water, accounted for 0.8 kg of it. Limb fat also rose by 1.1 kg, total weight by 2.7 kg, and there was no improvement in any strength or function measure. No trial exists in trained adults under 40, so the effect in that group is not established.

Does MK-677 cause water retention?

Yes, in the trials. The two-year study lists transient, mild lower-extremity oedema and muscle pain among its adverse effects, and reported a 0.8 kg increase in intracellular water in the treatment group. Researchers typically notice puffiness in the hands and ankles and a 1 to 2 kg scale rise in the first two to four weeks. It usually settles as dosing continues and clears within a fortnight of stopping. Track an ankle circumference alongside weight to tell it apart from tissue.

Does MK-677 make you hungry, and for how long?

Increased appetite was the most frequent adverse effect in the two-year trial, and the authors report that it subsided in a few months. It starts with the first doses because the compound is a ghrelin-receptor agonist, and it is the main reason participants gained more fat than lean tissue over the year. A calorie log from a baseline week is the only way to know whether a later weight change came from the compound or from the extra food.

What happens to blood sugar on MK-677?

It goes up in every study that measured it. Fasting glucose rose from 5.4 to 6.8 mmol/L over four weeks in older adults on 25 mg, an oral glucose tolerance test was impaired at two and eight weeks in obese men, and at one year fasting glucose was up 0.3 mmol/L with reduced insulin sensitivity. A baseline fasting glucose and HbA1c, repeated at four and twelve weeks, is the minimum a researcher should log. This is the most consistent adverse finding in the literature.

Do MK-677 results last after stopping?

The hormonal effects do not; GH and IGF-1 return to baseline once the compound clears, and the water weight leaves within about two weeks. No published trial followed participants off drug with a body-composition scan, so whether the kilo of fat-free mass persists is unknown. Given that strength never improved and part of the gain was intracellular water, the cautious assumption is that most of it reverses. The appetite increase also reverses, sometimes leaving a researcher eating far more than they need.

Research use only. The compounds discussed are sold as research chemicals and are not approved for human use. Nothing here is medical advice.