What did @alfsfitness actually say?
Four days into an MK-677 cycle sourced from TikTok Shop, @alfsfitness reports feeling bigger, lifting more, eating more, and generally feeling "great." He's honest enough to add, "it could be all placebo, I'm not too sure." That self-awareness is worth noting upfront. He's not claiming a transformation. He's documenting a feeling.
The visual comparison he shows is exactly as ambiguous as he admits. He acknowledges he might be tensing harder in the after photo. He's not selling a before-and-after miracle. He's journaling in public, which is a meaningfully different thing than making a health claim. That said, the video still implicitly frames MK-677 as responsible for positive changes in four days, and that framing deserves scrutiny.
Does the science back this up?
Some of it, partially. MK-677 is a ghrelin receptor agonist, meaning it mimics the hunger hormone. The appetite increase he describes is the most pharmacologically credible effect he mentions, and it can kick in quickly.
Ghrelin agonism does stimulate growth hormone secretion, and there is legitimate research here. Nass et al. (2008, Journal of Clinical Endocrinology and Metabolism) found that MK-677 increased GH and IGF-1 levels in older adults over 12 months. Svensson et al. (1998, Journal of Clinical Endocrinology and Metabolism) showed acute GH pulse amplification in healthy subjects. But here's the problem with day 4: IGF-1 downstream effects on muscle protein synthesis take weeks to accumulate meaningfully. Feeling stronger in four days is almost certainly neuromuscular confidence, training momentum, or caloric surplus, not anabolic tissue growth.
The strength and size gains he reports at day 4 are not supported by the pharmacokinetics of GH-axis compounds. This is a timeline problem, not a compound problem.
What did they get wrong (or right)?
He got the appetite effect right, even if accidentally. MK-677's most consistent and rapid effect in literature is increased hunger. If he's eating more, that tracks. Tannenbaum and Bowers (2001, Growth Hormone and IGF Research) noted appetite stimulation as a primary observed effect in ghrelin receptor agonism research.
What he got wrong is the implied timeline. "I'm definitely putting on size" and "my lifts are going up" at day four attributes results to a compound that simply hasn't had time to produce those results through its proposed mechanism. He doesn't explicitly make that causal link, but the video structure does it for him.
He also bought this from TikTok Shop. That's worth saying plainly. MK-677 is not FDA-approved for human use. It's sold as a research chemical. Products on TikTok Shop have no verified third-party testing or pharmaceutical-grade manufacturing standards. You don't know what you're actually taking, at what dose, or whether it matches the label. That's not a minor footnote.
What should you actually know?
MK-677 has a real pharmacological profile, and researchers have studied it. It's not snake oil. But the studies that show meaningful body composition changes run for months, not days. A 2008 study by Nass et al. ran for 12 months. A 1998 study by Murphy et al. in the American Journal of Physiology used extended treatment windows to observe meaningful GH axis changes.
Four days of subjective feeling better is not evidence of anything specific to MK-677. It could be placebo. It could be the training block he's in. It could be eating in a caloric surplus. The creator himself acknowledges this, which is genuinely responsible. But 34,600 viewers are not all going to hear that caveat.
There are also known side effects worth naming. Water retention is common and can mask or mimic rapid weight gain. Increased appetite can lead to fat accumulation alongside any lean mass changes. Insulin sensitivity concerns have been flagged in longer-term use. Nass et al. (2008) noted increased fasting glucose in their cohort. If you're considering MK-677 for any purpose, that conversation belongs with a licensed clinician, not a TikTok comment section.