MK-677 for weight gain: separating real effects from TikTok hype

What did @s197.eduardo actually say?

Honestly, the video's audio is a song, not a voiceover. The actual claim lives entirely in the caption: "Was stuck at 130lbs for the longest time and ate so much. Just couldn't gain weight till i started doing Mk. Now currently at 160lbs." That's a 30-pound gain attributed directly to MK-677. He also self-identifies as "a rookie not professional," which matters.

There's no dosing information, no protocol, no timeline, and no mention of training changes or diet specifics beyond "ate so much." The claim is essentially: I was a hardgainer, I took MK-677, I gained weight. That's the whole argument. It's worth taking seriously, but it's also worth unpacking what that weight actually represents, because 30 pounds on a body is not all the same thing.

Does the science back this up?

MK-677 (ibutamoren) can absolutely cause weight gain. That part isn't disputed. The mechanism is real: it's a ghrelin receptor agonist that stimulates growth hormone and IGF-1 secretion. Studies confirm these effects. The question is what kind of weight gain and at what cost.

Svensson et al. (1998, Journal of Clinical Endocrinology and Metabolism) found that MK-677 increased lean body mass and GH secretion in healthy older adults. A longer 2-year trial by Nass et al. (2008, Journal of Clinical Endocrinology and Metabolism) confirmed GH and IGF-1 elevation but also flagged increases in fasting glucose and insulin resistance. Murphy et al. (1998, Journal of Clinical Endocrinology and Metabolism) showed it stimulated appetite significantly, which aligns with what Eduardo describes: eating more and finally gaining weight. So the biology checks out. But "weight gain" in MK-677 literature frequently includes water retention and increased appetite-driven caloric intake, not just lean muscle. A 30-pound gain with no body composition data is an incomplete story.

What did they get wrong (or right)?

Credit where it's due: he called himself a rookie, not a coach. That's more honest than most of these videos. And the experience he describes, an ectomorph struggling to eat enough who then gained weight after appetite stimulation, is pharmacologically plausible.

What's missing is context that matters. MK-677 reliably raises appetite and causes fluid retention. Some of that 30 pounds is almost certainly water. Without a DEXA scan or even before/after body fat estimates, "160lbs" tells you nothing about muscle versus fat versus water. Studies like Nass et al. (2008) also documented that roughly half of participants on long-term MK-677 experienced peripheral edema. Ghrelin receptor agonism also elevates cortisol transiently and can impair insulin sensitivity, which are not small side effects for someone whose baseline health metrics we know nothing about. The caption frames this as a simple win. The science says it's more complicated than that.

What should you actually know?

MK-677 is not approved by the FDA for any indication. It is not a SARM, though it is often grouped with them. It is a research compound. That means it's used off-label, the quality of unregulated sources varies dramatically, and long-term safety data in young, healthy adults is essentially nonexistent.

The short-term studies that do exist (mostly in elderly or growth hormone-deficient populations) show real physiological effects, but also consistent flags around blood glucose and insulin sensitivity. If you're a young person with family history of diabetes or pre-diabetes, those signals deserve serious attention. MK-677 also does not require injections, which makes it accessible, but accessibility is not the same as safety. Anyone considering it should do so under medical supervision with baseline labs including IGF-1, fasting glucose, and HbA1c. A 49,000-view TikTok caption is not a clinical protocol.

Bottom line

Eduardo's weight gain story is biologically plausible. MK-677 does stimulate GH, raises IGF-1, increases appetite, and can facilitate weight gain in people who struggle to eat enough. None of that is fabricated. But 30 pounds over an unspecified timeline with no body composition data, no labs, and no side effect disclosure is an incomplete picture. The science supports the mechanism. It does not support treating this caption as a template for your own protocol.