Dave Asprey's peptide claims: what the science actually supports

What did @daveaspreyofficial actually say?

Asprey told his interviewer there are peptides that let you lose belly fat without exercising or changing your diet. He named two specifically: "SLUPP32" and MK-677. He called MK-677 "magic" and claimed it "causes your body to grow new mitochondria" in a way similar to exercise. He also repeated his often-cited personal story about exercising 90 minutes a day, six days a week for 18 months and failing to lose weight, concluding that "exercise doesn't help you lose weight very much at all."

To be clear about what was claimed: a person can eat junk food, skip the gym, take these compounds, and lose belly fat. That is a very specific, testable claim, and it deserves a direct answer.

Does the science back this up?

Partially, but not in the way Asprey framed it. MK-677 is a ghrelin receptor agonist that stimulates growth hormone secretion, and some research does show it increases lean mass. But fat loss without dietary changes? The evidence is thin.

A 2008 randomized controlled trial by Nass et al. in the Annals of Internal Medicine found MK-677 increased growth hormone and IGF-1 levels in older adults, and improved lean body mass, but it also increased fasting blood glucose and did not produce meaningful fat loss. A 2019 review by Sigalos and Pastuszak in Sexual Medicine Reviews noted MK-677's anabolic effects come with metabolic tradeoffs, including insulin resistance, which is the opposite of what someone eating junk food needs. As for SLUPP32, the research is almost entirely preclinical. A 2020 study by Zhu et al. in Cell Metabolism found the SLUPP32 receptor pathway involved in mitochondrial function in mice, but there is no compound named "SLUPP32" commercially available or tested in humans as a peptide therapy. Asprey appears to be referencing a receptor target, not an actual drug.

What did they get wrong (or right)?

Let's give credit where it's due: Asprey's point that exercise alone is a poor driver of weight loss is actually well-supported. The compensatory appetite response to exercise is well-documented, and researchers like Herman Pontzer have written extensively about how total daily energy expenditure adapts. His personal anecdote aligns with real physiology here.

But calling MK-677 "magic" that causes fat loss while eating junk food is not supported. MK-677 is not a peptide, it is a small-molecule secretagogue, and the FDA has not approved it for any use. It raises IGF-1, which has its own long-term cancer-risk questions. Several researchers, including Laron in a 2001 paper in Pediatric Endocrinology Reviews, have flagged IGF-1 elevation as a potential promoter of certain tumor types with chronic use.

The SLUPP32 claim is the bigger problem. Presenting a mouse-model receptor pathway as something you can take to burn fat is misleading at best. There is no human-ready SLUPP32 compound. Telling 244,000 viewers otherwise is irresponsible.

What should you actually know?

If you are genuinely interested in peptide therapy or growth hormone secretagogues for body composition, there is legitimate clinical work being done, but it looks nothing like "eat junk food and take this." Any responsible approach involves baseline labs, a licensed prescriber, and honest monitoring of insulin sensitivity and IGF-1 levels.

MK-677 does show real effects on growth hormone pulse amplitude and lean mass in clinical settings. It is not a toy, and it is not appropriate for unsupervised use. It is currently classified as a research chemical and is not FDA-approved. Compounded versions exist but their quality varies significantly across suppliers.

The broader framing here, that there is a shortcut to body composition change that bypasses diet, is a claim that sells supplements and podcasts but does not hold up in longitudinal outcome data. The DIETFITS trial (Gardner et al., 2018, JAMA) and decades of obesity research consistently show diet quality and caloric balance are the dominant variables. Peptides can be adjuncts in clinical contexts. They are not replacements for foundational metabolic health.