Among the many uses and types of therapeutic peptides, the topic of peptides for muscle growth is drawing increased interest among the research community and the public at large.
Any gym-goer knows that building muscle is difficult on the best of days, and requires dedication to a strict workout routine and a nutrition protocol.
For these reasons, it’s no surprise that scientists are increasingly looking into peptides as compounds that may aid in hypertrophy or muscle growth processes.
Here are the best peptides for muscle growth, along with a review of the safety and effectiveness of peptides for bodybuilding.
Top 3 Peptides for Muscle Growth
Based on the research available to date…
Here are three of the best peptides for bodybuilding:
Ipamorelin: Best Overall Peptide for Muscle Growth CJC-1295 DAC: Best Peptide for Improving Body Composition 5-Amino-1MQ: Best Peptide for Maintaining Muscle Mass
What Are Peptides?
Peptides are unique compounds that may offer several benefits for a huge number of health conditions and concerns.
In recent years, they have grown in popularity and general interest as they receive more attention from both researchers as well as the health optimization and biohacking communities.
Structurally, peptides are short chains of amino acids — typically consisting of up to 50 amino acids linked together. Amino acids are the “building blocks of protein,” or — in this case — the building blocks of peptides.
Longer chains consisting of 51 or more amino acids are categorized as proteins.
With the many amino acids scientists have identified, and the endless configurations they could exist in to form different peptides, there is huge potential for these compounds for a number of health applications.
To date, more than 80 peptide drugs have been approved worldwide, and the industry’s rapid growth is predicted to continue, with numerous peptides under avid clinical analysis for their myriad therapeutic benefits.
Studies support the effectiveness of various peptides in a range of clinical areas, from injury recovery to the treatment of inflammatory and cardiovascular diseases.
Currently, peptides are being used for:
Muscle growth
Weight loss
Immune support
Anti-aging
Skin health
Disease prevention
Inflammation
Apart from their many potential benefits, peptides are advantageous for their favorable safety profiles, relatively low production costs, and as less invasive alternatives to traditional medical treatments.
Ongoing technological advances in peptide routes of administration and formulations have led to increases in bioavailability and more targeted therapeutic effects. Leading researchers are optimistic about the future of this novel pharmaceutical field.
How Do Peptides Work for Bodybuilding?
There are several different classes of peptides, and each of them works in slightly different ways.
Our top two picks for muscle-building peptides, Ipamorelin and CJC-1295 DAC, are both growth hormone secretagogues.
They signal the body to produce more growth hormone, which is what potentially triggers increased muscle growth.
However, in order for peptides to help with muscle building, engaging in muscle-building activities is a necessity. These include:
Resistance training utilizing progressive overload (increasing weight, reps or sets over time to pose a continuous challenge to the body).
A surplus of calories and protein provides the raw materials the body needs to synthesize new muscle tissue.
Adequate periods of rest and recovery, including good sleep and low stress — because new muscle tissue is built during rest periods, not during workouts.
Peptides mostly likely do not directly stimulate new muscle growth in healthy individuals — training is still required. But, they could make conditions more favorable for optimal muscle growth.
Does Peptide Therapy for Muscle Growth *Actually* Work?
There are many factors that impact the efficacy of peptide therapy for muscle growth. These include:
The type of peptide chosen
Dosage and administration schedule
Consistency with peptide administration
Workout routine
Nutrition
Rest and recovery
Age, sex, and current health status
Not to mention, there is still not a lot of research to support many of the peptides we discuss below, particularly in human subjects. Although the small amount of existing research does appear pretty promising, there is no definitive evidence for these peptides’ ability to promote hypertrophy in healthy adults.
Instead of counting on peptide therapy to grow muscle, it may be considered a supplementary addition to a solid muscle-building routine. It can help make conditions more favorable for muscle growth, but merely taking a peptide is unlikely to cause muscle growth by itself.
It is still important to stimulate the body’s natural healing process by damaging the muscle tissue through strength training, and then recovering properly — allowing the muscles to heal. This is where muscle growth happens.
Best Peptides for Bodybuilding and Gains
There is a seemingly endless number of research peptides, all with different functions and potential benefits.
Here are seven that are among the best suited for muscle growth, along with a quick review of how they work, a summary of existing research, and a verdict on their usefulness for muscle hypertrophy.
1. Ipamorelin
Ipamorelin is a synthetic growth hormone-releasing peptide and a ghrelin mimetic. Essentially, it acts like the hormone ghrelin and is able to bind to ghrelin receptors in the pituitary gland. In doing so, it stimulates the release of growth hormone-stimulating hormone — which signals the body to secrete growth hormone [1].
While there are many other peptides that act as ghrelin mimetics similarly to ipamorelin, they also activate the body’s stress response — sending it into “fight or flight” mode. A unique advantage of ipamorelin is that it does not activate this stress response [2].
Still, there has not been a great deal of published research on ipamorelin. Most of the research that exists was done in animals, so it is considered “pre-clinical.”
Because it stimulates the release of growth hormone, researchers have found that ipamorelin may help to stimulate new bone, muscle, and blood vessel tissue formation [3, 4, 5].
All of these effects would offer body composition advantages, boosting lean (fat-free) body mass.
However, what we are most interested in right now is muscle growth. In one rat study, researchers investigated the effect of ipamorelin on bone damage caused by glucocorticoids. Rats were administered glucocorticoids, which induced bone damage, and then a subgroup was administered ipamorelin. The researchers noted that the ipamorelin-treated group not only had their bone damage reversed, but showed significantly increased muscle strength [4].
On that note, ipamorelin is banned for use in sport by the World Anti-Doping Organization (WADA) and related bodies, signaling that it does convey some kind of performance advantage above and beyond typical sports supplements and therapies.
Still, more research is needed before we can fully understand the effects of ipamorelin — especially on human muscle growth.
CJC-1295 is a synthetic analog of growth hormone-releasing hormone. Like ipamorelin, it stimulates the pituitary gland to release growth hormone. It was originally developed to assist with excess fat accrual in people with HIV/AIDS, but trials were discontinued after one of the participants died.
Although study researchers determined the death was not related to CJC-1295, its pharmaceutical potential has been abandoned for now [6].
Many CJC-1295 peptide products on the market are made with Drug Affinity Complex (DAC), which helps the compound bind to blood proteins and gives it a much longer half-life over CJC-1295 without DAC. While CJC-1295 DAC has a half-life of about one week, the no DAC version fully clears from the body in about an hour [7, 8].
CJC-1295 significantly increases blood levels of growth hormone and insulin-like growth factor-1, making it a promising option for muscle growth.
Both growth hormone and insulin-like growth factor-1 could theoretically promote muscle growth in healthy subjects, but this has not been tested in published research. Additionally, the link between CJC-1295 and muscle growth has not been extensively studied [9].
Still, CJC-1295 may offer other benefits for muscle growth and body composition. As noted, it was originally developed to assist HIV/AIDS patients suffering from lipodystrophy, a disorder of fat accumulation.
Additionally, CJC-1295 may help to improve sleep quality. Researchers have found that the peptide’s parent, growth hormone-releasing hormone, could reduce cortisol levels at bedtime, as well as increase rapid-eye-movement (REM) sleep and slow-wave sleep [10].
Given the important roles of sleep and recovery in muscle building, this is yet another way that CJC-1295 may help to promote hypertrophy.
5-amino-1MQ is a synthetic version of a compound called methyl quinolinium, a nicotinamide N-methyltransferase (NNMT) inhibitor. The significance of this is that there is a research-backed link between NNMT and metabolic disorders, like obesity.
Therefore, researchers have been investigating the potential of NNMT inhibitor compounds, including 5-amino-1MQ, as anti-obesity agents [11].
In mice, researchers have found that 5-amino-1MQ could help to reverse obesity and lower total cholesterol levels with no side effects [12].
These changes may be related to the way 5-amino-1MQ affects the gut microflora [13].
However, it also offers some benefits related specifically to muscle growth. Independent peptide researchers have noted that 5-amino-1MQ also helps with the creation of new muscle tissue, and makes it easier to recover from intense workouts. Overall, this results in a more efficient, faster muscle-building process.
For simultaneous fat loss and muscle growth, 5-amino-1MQ is recommended because of its “dual action” potential, as it can actually promote both fat loss and muscle growth at the same time. Unlike most peptides, 5-amino-1MQ has high oral bioavailability and is typically available in capsule form.
4. MK-677
MK-677 is actually not a peptide. However, like ipamorelin, MK-677 functions as a ghrelin analog and stimulates the production of growth hormone and insulin-like growth factor-1 in the pituitary gland [14].
Also comparably to ipamorelin, MK-677 can also stimulate growth hormone with minimal effects on the body’s cortisol level — so it does not cause the same amount of stress response as other compounds that stimulate growth hormone [14].
Additionally, like 5-amino-1MQ, MK-677 is designed to be taken orally, making it another injection-free alternative to many of the peptides featured on this list [14].
Since 1996, there have been a number of studies on MK-677 in both animals and humans.
In one notable study, researchers found that MK-677 could help preserve lean body mass in obese men while they were losing weight, which is advantageous because weight loss is often accompanied by losses in lean mass (muscle and bone). This can affect overall health and bone strength, and lower metabolic rate, making it even more of a challenge to continue to lose fat [15].
5. Sermorelin
Sermorelin is an analog of growth hormone-releasing hormone, so like many of the other peptides on this list, it works by increasing growth hormone production. It was originally developed and approved by the U.S. Food and Drug Administration (“FDA”) for the treatment of growth hormone deficiency, but its approval was discontinued in 2008 for commercial (not safety) reasons. This means that sermorelin is no longer available as a medication, just a research chemical [16].
Researchers have found that sermorelin may help promote lean body mass gains in men with clinical and subclinical hypogonadism (low testosterone and other sex hormones). However, it is not known if Sermorelin would have the same muscle-boosting effect on otherwise healthy men [17].
6. Follistatin 344
Follistatin is a naturally occurring protein found in nearly all human cells, and follistatin 344 is a synthetic version of this protein. It inhibits the action of myostatin, a compound that down-regulates muscle growth [18].
In animal studies, follistatin administration has been shown to significantly increase muscle mass. However, it is important to note that this research was done in animals with muscular disorders. It is not clear if follistatin would offer the same benefits in healthy animals, or in healthy humans, so more research is needed [19, 20].
7. Tesamorelin
Tesamorelin is another growth hormone-releasing hormone analog that was originally developed to treat lipodystrophy in HIV/AIDS patients. It is currently available for that purpose under the brand name Egrifta [21].
However, researchers have noted potential other benefits, including muscle mass improvements. In one 2019 study in HIV patients, researchers noted that those who experienced fat loss from tesamorelin administration (“tesamorelin responders”) subsequently displayed increases in muscle area and density [22].
Still, it is not clear if the same effect would occur in people without HIV, so more studies on healthy test subjects are warranted.
Peptide Side Effects and Safety
There is not a lot of research on the majority of the compounds discussed above, so caution and vigilance are warranted.
We do know that some of the most common side effects of injectable peptides are related to the delivery method, and include injection site pain, redness, or swelling.
Here is a quick rundown of some of the known side effects and safety concerns of each of the muscle growth compounds covered above:
Ipamorelin may cause face flushing and increased appetite [23, 24]. It has not been FDA-approved for any use in humans.
CJC-1295 may cause hives, nausea, anxiety, irritability, headache, or flu-like symptoms [25]. It has also been observed to cause side effects like flushing, water retention, and insomnia, which cease upon discontinuation of therapy [6, 7].
5-Amino-1MQ is primarily used for weight loss, so it may cause weight reduction (even if unwanted). It also affects the gut microbiome, which may cause digestive tract issues [12].
MK-677 may cause increased blood glucose, insulin resistance, increased appetite, mild edema, muscle pain, decreased cholesterol, and/or increased cortisol [26]. It is also important to note that two separate studies on MK-677 have been discontinued: one in children for an unknown reason, and one in elderly people with hip fracture because it appeared to increase congestive heart failure risk [27, 28].
Sermorelin may cause face flushing, vomiting, headache, paleness, pain, nausea, and taste changes [29]. Its FDA approval was withdrawn in 2008 for reasons unrelated to safety or effectiveness [16].
Follistatin 344 may cause muscle soreness and swelling, although this could be due to training itself [30].
Tesamorelin may contribute to insulin resistance and increase risk of type 2 diabetes [31]. Currently, it is FDA-approved to treat HIV-associated lipodystrophy.
Research subjects with preexisting medical conditions or who are taking prescription medications should be properly screened prior to being included in a study involving any one of these compounds.
When preparing peptides for injection, it is important to follow best practices for reconstitution and storage and source research-grade materials, including bacteriostatic water.
Do Peptides Work Like Steroids Would?
Peptides and steroids are often lumped together. It is true that they are both considered “performance enhancers.” And peptides are often erroneously thought to be equivalent to steroids because both are commonly administered via injection.
However, there are few true similarities between these two categories of compounds. Steroids and peptides are very different.
As mentioned above, peptides are short chains of amino acids. They may help to increase muscle mass, as long as the other “ingredients” are there — progressive overload and protein/calorie surplus.
On the other hand, anabolic steroids are lab-made versions of the hormone testosterone, which is the dominant sex hormone in men and is associated with increased muscle mass.
Anabolic steroids are more powerful than peptides from a muscle-building standpoint because testosterone, including lab-made testosterone, is a more direct muscle-builder.
However, anabolic steroids also have more downsides, such as an increased risk of infertility, hair loss, and acne [32].
As we discussed above, peptides have varying mechanisms of action and may help promote muscle growth depending on these mechanisms.
On the other hand, anabolic steroids all bind in varying ways to bind the androgen receptors and work much like natural testosterone.
Overall, peptides are generally a safer option. They cannot override the body’s natural testosterone threshold as do anabolic steroids. Instead, they can be used to help optimize the body’s natural hormone production.
Concerns and Caveats
Here are a few of the potential downsides of peptides for muscle growth to be aware of.
Peptides are not the best compounds for hypertrophy
While peptides are powerful, they may not be the best tools available for muscle growth. There are other compounds that may be more effective (like anabolic steroids), although these tend to have more associated risks.
The effects of peptides on hypertrophy are likely going to seem minuscule in comparison to these other compounds.
Peptides are not magic bullets for muscle growth
Peptides should not be thought of as a shortcut or a “hack” for muscle growth. Administering peptides with this expectation is likely going to result in disappointment.
Peptides should be viewed as a component to a muscle growth strategy, which includes other basic ingredients like:
A good workout routine that prioritizes progressive overload
Adequate calorie and protein intake
Appropriate periods of rest
The addition of peptides may help the hypertrophy process happen more quickly or more efficiently, but peptides will not magically result in new muscle growth unless the fundamentals are also in place.
Peptides for muscle growth are banned in competitive sports
Thinking about testing peptides in preparation for competition, or for an edge at a sporting event?
You may want to reconsider.
Many peptides are enumerated by the Prohibited List of the World Anti-Doping Agency (WADA) Prohibited List, meaning that they are banned from sporting competitions subject to WADA rules and standards [34].
The World Anti-Doping Agency’s standards are used to develop more local standards, so this ban is pretty universal across organizations that implement some form of anti-doping.
Competitive athletes are advised to build muscle the old-fashioned way: resistance training with progressive overload, plenty of protein intake, and eating at a caloric surplus.
Peptides and Bodybuilding | Verdict
Peptides for muscle growth show a lot of promise, but more research is needed overall. Most existing research on peptides for muscle growth is done in animals, or in patients with muscular disorders that affect how the body builds new muscle.
Still, independent researchers may be curious about the effects of these peptides on muscle growth in healthy adults.
Still, remember that peptides are not going to be a “quick fix” for muscle growth. A solid exercise, nutrition, and recovery plan will still be essential to see results.
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