Before You Try Peptides: What a Clinical Researcher Wants You to Know First

Gabriel Alizaidy, MD, MS is Scientific Director at Maximus, a precision health and performance medicine company, where he leads clinical research, designs hormone and peptide protocols, and trains providers across the US on how to apply them. Before joining Maximus he worked on CAR-T therapy trials at UChicago Medicine. 

What makes his perspective distinctive is what sits behind it: not just published literature, but real-world clinical data generated across thousands of patients, tracked across protocols, adjusted in real time. 

Most of the conversation around peptides and GLP-1 drugs is built on thin published evidence and secondhand interpretation. Gabriel is working from a different dataset entirely. 

In this interview, he shares what that data is telling him about GLP-1 beyond weight loss, which peptides are delivering consistent results, and what to have in order before starting any protocol.​​​​​​​​​​​​​​​​

1. You develop peptide and hormone protocols grounded in clinical research and see real outcomes every day. What do you know from that work that most people researching peptides on their own will never pick up?

Someone looking at peptides online will find a mechanism of action, a dosing range, and a list of reported benefits. What they won't find is how those peptides behave inside a body that already has its own hormonal landscape, inflammatory load, and metabolic state. A peptide that produces a clear response in one person can do almost nothing in another, and the difference is rarely the compound. It's the environment it's being introduced into. Someone with uncontrolled insulin resistance won't get the same growth hormone response from CJC-1295 or tesamorelin as someone with normal glucose metabolism.

Most people also stack peptides simultaneously because they read about a "protocol" online. For optimal results, you address sleep, diet, exercise, and get metabolic markers in range before layering anything else on top. The order you do things in changes the result as much as the things themselves.

2. Which peptides are delivering consistent, measurable results right now, and what are you seeing in terms of outcomes?

Tirzepatide and retatrutide are the current kings. Tirzepatide is a dual GLP-1/GIP agonist with published trial data showing roughly 20% total body weight loss over 72 weeks, plus strong lipid and liver fat improvements. 

Retatrutide adds a glucagon receptor to that, making it a triple agonist, and the Phase 3 data is showing 22 to 24% weight loss at 48 weeks with 85 to 90% resolution of fatty liver disease. The cardiovascular, hepatic, and anti-inflammatory data on both grows with every top line result announced.

BPC-157 and TB-500, colloquially referred to as the wolverine stack, are the most widely used tissue repair peptides. BPC-157 upregulates VEGF for new blood vessel formation at the injury site and increases GH receptor expression locally. TB-500 promotes cell migration and reduces fibrosis through a separate mechanism.

KPV, a fragment of alpha-MSH, is gaining traction for gut inflammation and mucosal repair. 

GHK-Cu regulates over 4,000 genes involved in tissue repair and antioxidant defense, with documented effects on collagen synthesis, wound healing, and bone repair. Plasma levels of GHK-Cu drop from around 200 ng/mL at age 20 to about 80 ng/mL by age 60, which is a large part of why it's getting attention in the beauty and longevity space. 

All four of those together make up the KLOW stack, and the combination has a following because each compound targets a different part of the repair and regeneration process.

3. GLP-1 protocols are everywhere. Beyond weight loss, what are you observing clinically that the mainstream conversation is missing?

Most of the public conversation frames GLP-1 agonists as weight loss drugs that happen to have a few bonus effects. The clinical reality is closer to the opposite. Weight loss is a downstream effect of broader cellular and metabolic changes, and the data on those other effects is, in several cases, stronger than the weight loss data.

I talk about the cardiovascular evidence more than anything. The SELECT trial enrolled over 17,000 non-diabetic people with obesity across 41 countries and showed roughly a 20% reduction in major adverse cardiovascular events. GLP-1 agonists stabilize atherosclerotic plaque by reducing monocyte adhesion, inhibiting foam cell formation, and increasing fibrous cap thickness. 86% of heart attacks come from unstable plaques causing less than 70% stenosis, meaning they're clinically silent before they rupture, so plaque stabilization changes the calculus on cardiovascular risk in a way that blood pressure and cholesterol management alone do not. 

The neurological data is early, if not premature, but two published RCTs show exenatide (an older generation of GLP-1) slows Parkinson's progression, and a pilot trial showed liraglutide (also an older generation of GLP-1) prevented decline in brain glucose metabolism in Alzheimer's over 6 months.

The liver numbers are the ones I keep coming back to. Semaglutide achieved 59% NASH resolution (the most severe form of nonalcoholic fatty liver disease (NAFLD), a condition in which the liver builds up excessive fat deposits) vs. 17% placebo in a 72-week trial. 

Retatrutide resolved fatty liver disease in 85 to 90% of participants. NAFLD now exceeds hepatitis C as the leading indication for liver transplant, and if these numbers hold at scale, this drug class changes that trajectory.

4. How do you approach combining peptides with hormone optimization? 

Hormones and peptides aren't separate categories you stack on top of each other. They interact. 

Optimized testosterone changes how GH peptides perform because testosterone increases nitrogen retention and protein synthesis, so when you add CJC-1295 or ipamorelin on top of that, the body has a better anabolic environment to respond to the GH pulse. 

Optimized thyroid function changes how metabolic peptides perform because T3 drives basal metabolic rate, and a GLP-1 agonist introduced into someone with untreated hypothyroidism is fighting a metabolic floor it can't lower on its own. 

The hormone part of the puzzle should have priority because it sets the conditions for everything that follows.

5. Before someone starts a peptide protocol, what bloodwork and baseline markers should they have in hand, and what are they looking for?

At minimum: CBC, CMP, lipids, fasting insulin, CRP, ApoB, ApoA1, lipoprotein(a), a full sex hormone panel, thyroid panel, IGF-1, vitamin D, B9, B12, RBC magnesium, and homocysteine. That covers metabolic health, inflammatory status, cardiovascular risk, hormonal landscape, and nutrient status before anything new enters the picture.

This is a starting point. More labs will be needed depending on context, goals, and specific pain points. 

Someone focused on GH needs a solid IGF-1 baseline to measure response against. Sex hormones are often a straightforward fix that changes how everything else responds. 

You want to understand the landscape before you change it, so that when you recheck you can actually tell whether the protocol is doing what it should or whether something needs to change.

6. What does a well-structured peptide cycle actually look like in practice? Duration, dosing adjustments, when to stop, when to reassess.

Run a peptide for the duration it's needed and not longer. Some compounds lend themselves to extended use, and real-world evidence supports longer protocols for GH peptides like CJC-1295 and ipamorelin without significant issues. For GLP-1 agonists, you don't need to max out the dose to get results, and splitting the dose can reduce side effects. The goal is to find the minimum effective dose that produces the outcome you're after.

Tissue repair compounds like BPC-157 and TB-500 are typically run for the duration of the healing process and then stopped. Immune peptides like thymosin alpha-1 can be dosed more aggressively for acute illness and then stepped down. 

Every protocol needs a clear reason for starting, defined markers of progress, and a point where you stop or adjust based on what the labs and the response are telling you.

7. How do you think about peptides within a broader health stack alongside nutrition, training, and sleep?

Sleep, nutrition, training, and stress management come first. Growth hormone release peaks during deep sleep, so a GH peptide in someone sleeping five hours a night can't produce a full pulse because the body doesn't spend enough time in that phase. Someone eating 60 grams of protein a day doesn't have the amino acid availability for tissue repair or lean mass preservation regardless of what compounds they're on.

GLP-1 drugs have been documented to cause muscle loss, or so the narrative goes. They reduce appetite, and if someone eats less protein as a result, they lose lean mass. That's a nutrition problem. GH peptides don't build muscle without resistance training either. The peptide amplifies the training stimulus, and if there's no stimulus, there's nothing to amplify.

If gut dysfunction is driving elevated systemic inflammation, that inflammatory state blunts the response to nearly everything else you introduce. Fix the gut before or alongside any protocol, and everything downstream works better.

8. What are the most common mistakes you see in how people use peptides, and what are the real risks people underestimate?

Research-use-only peptide use is widespread, and while I don’t condone it, it’s a reality that we all have to face. But for anyone who goes down that path, verifying what you're actually putting in your body is the first step, before protocol design even enters the conversation. 

Request third-party testing, verify purity documentation, and do all the legwork before assuming a vial contains what the label says. If a supplier can't provide that documentation, find a different supplier.

9. For our European readers, what does access to quality peptide protocols look like right now?

Regulatory frameworks vary by country, and some peptides that require compounding pharmacies and off-label justification in the US are available as approved drugs in parts of Europe. Thymosin alpha-1 is one example, approved in several European countries while remaining non-FDA-approved in the US.

Most peptides used clinically have no formal regulatory approval for their common indications anywhere in the world. BPC-157 has no regulatory approval for pain or healing on the entire planet. The quality standard is the same regardless of where you are: cGMP-certified manufacturing, third-party purity testing, and documentation you can verify. That burden falls on the individual and the provider whether you're in the US, the UK, or anywhere else.

10. Across peptides, small molecules, and advanced therapies, what should someone optimizing their health today be watching for in the next two to three years?

The other thing I think about is real-world evidence aggregation. Thousands of clinicians are working with these compounds daily, collecting labs, tracking outcomes, adjusting protocols, and that data sits in isolated charts across hundreds of practices with no systematic way to aggregate it. 

If we can build infrastructure to collect and analyze those outcomes at scale while protecting privacy, we close the gap between what providers observe and what the published literature formally supports. BPC-157 is the clearest example: two decades of clinical use, strong preclinical data, consistent provider-reported outcomes, and zero published human RCTs. That gap doesn't exist because the compound doesn't work. It exists because no one has built the system to formalize what providers already see. That's the problem I think about most.