What are Peptides

By now I’m sure you’ve heard of the word peptide thrown around, maybe it was on a listicle or you saw a billboard for Collagen Peptides.

It’s hard to not walk into a store and see multiple peptide-based products promoting anti-aging, muscle growth, and other attractive promises

In this article we will be looking at the science behind peptides, what they are, the sources, how specific peptides work as well as the safety and research behind them.

Warning: The content on Muscleandbrawn.com and the information included in this article is intended for entertainment and informational purposes only. It is not intended nor implied to be a substitute for professional medical advice. Prior to buying anything, check that it is compliant where you live with your current government laws. We frequently mention research chemicals that are not made for human consumption. Therefore, before purchasing any product for personal use, consult with your doctor or healthcare provider first.

What are Peptides and why should I care?

Peptides are smaller versions of proteins made up of amino acids- the building blocks of protein. Where proteins are long chains made up of more than 50 amino acids, peptides are shorter and made up of 2-50 amino acids. Since they are shorter than proteins, our bodies can digest and absorb them more easily than proteins (1).

How do Peptide’s work?

Peptides often act as hormones sending information through our blood from one site to another and stimulating our cells to produce various chemicals that can have beneficial effects on our bodies (2).

Where can I find them?

Peptides are naturally made in our body, can be found naturally in food sources, and be made synthetically by labs.

Food products that contain peptides include:

  • Meat
  • Fish
  • Legumes
  • Soy
  • Oats
  • Flaxseeds
  • Hemp seeds
  • Wheat

Peptides made synthetically in a lab are usually bioactive peptides that mimic or influence the natural peptides in our body. These peptides will have different properties depending on the sequence of amino acids (2).

There are many health benefits of peptides, the most common being:

  • Muscle Growth
  • Weight Loss
  • Anti-Aging
  • Improving the skin barrier
  • Lowers the blood pressure
  • Acts as antioxidants
  • Improving the immune function

There are multiple bioactive peptides on the market however the most common ones are:

Forms of Peptides:

Peptides come in a variety of forms depending on their use. Peptides to aid in anti-aging are commonly found in the form of lotions and face masks, however peptides to aid in muscle growth, weight loss and injury recovery are commonly found in a supplemental powder or injectable form (3).

Peptides in skincare

Common peptides in skincare are:

  • Collagen
  • Antimicrobial peptides

Collagen, elastin and AMPs are important components that are found in healthy skin and play an important role in anti-aging, wound healing and skin recovery.

Our bodies naturally make collagen, however as we age the production declines. This leads to those dreaded fine lines and skin that is not as bright or even.

The Collagen molecule is too large to be absorbed through the skin and is commonly taken as a supplement in an ingestible form.

Peptides however can be absorbed by the skin and are a common ingredient added to skin care products. Collagen is made up of three polypeptide chains so adding peptides to skincare products can stimulate collagen production.

The skin barrier is our body’s line of defense against bacteria, ultraviolet rays and other toxins. This barrier can be damaged from exposure to toxins, over-exfoliation and even poor sleep. Peptides help build up a stronger barrier and prevent further damage to the skin.

Peptides can help ease inflammation, repair damaged skin and even out skin tone. Certain peptides are antibacterial and these properties can help assist to reduce acne.

Peptides also include elastin fibers, these fibers help make our skin look firmer. As we age the elastin production reduces so adding them to skincare products will help make our skin firmer (3).

How do Collagen peptides and antimicrobial peptides (AMPs) work?

Collagen peptides assist the skin in firmness and reduce the appearance of aging lines.

There are numerous AMPs and each with different health benefits. Notable ones include an AMP that produces melanin- a peptide improving protection against the sun and another AMP that is involved in skin whitening.

Peptides for bodybuilding

Common peptides used for bodybuilding are:

Growth hormone secretagogues (GHS) are a group of peptides commonly used for body building as they can stimulate the production and release of human growth hormone (HGH).

HGH helps to boost muscle growth and promote fat loss however, due to its side effects taking HGH directly is banned. GHS are considered a natural and safer alternative to HGH with less side effects.

Peptides for Weight Loss

Common peptides for weight loss include

  • Growth-hormone releasing hormones- sermorelin, tesamorelin and CJC-1295
  • Growth hormone-releasing peptides (GHRPs)- GHRP-6
  • Ghrelin and other mimicking compounds- ipamorelin, macimorelin
  • Mitochondrial derived peptides- MOTS-c
  • Peptide fragment- AOD9604
  • Serotonin-noradrenaline dopamine reuptake inhibitor- tesofensine

There are many peptides used for weight loss with some sharing the function of being used in bodybuilding such as sermorelin and ghrelin.

The weight loss effects of tesofensine were first noticed in Alzheimer’s and Parkinson’s trials whilst in recent years new peptides such as MOTS-c and AOD9604 have been found.

How do Growth hormone-releasing peptides and hormones (GHRPs) work?

Growth hormone secretagogues (GHS) are a group of peptides commonly used for body building as they can stimulate the production and release of human growth hormone (HGH).

HGH is a hormone secreted by the pituitary gland, can enhance muscle growth and promotes the loss of body fat. This is done by stimulating the liver to release insulin-like growth factor-1 (IGF-1).

IGF-1 triggers muscle protein production and muscle growth. It also indirectly promotes the breakdown of body fat (3).

How do Ghrelin and other mimicking compounds work?

Ghrelin is a hormone produced mainly in the stomach with the small intestine, pancreas and brain producing small amounts. It has numerous functions in our body and has been dubbed the ‘hunger hormone’ as it stimulates appetite, increases food intake, and promotes fat storage.

Ghrelin and other compounds mimicking it bind to the GHS receptor and stimulate the release of growth hormone from the pituitary gland. This release of growth hormone breaks down fat tissue and increases muscle growth. These peptides are used to aid in weight loss, increasing muscle and can assist in muscle recovery (4).

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How do mitochondrial derived peptides work?

MOTS-c is a relatively new peptide derived from the mitochondria and is referred to as an exercise mimetic. This means that it mimics or enhances the therapeutic effects of exercise.

In response to metabolic stress and regulation of adaptive nuclear gene expression MOTS-c can translocate to the nucleus of a cell. Research shows that it can enhance the oxidation of lipids, decrease fat gain on a high fat diet, turn glucose into usable energy and can control insulin sensitivity (5).

How do peptide fragments work?

AOD9604 is a modified form of an amino acid that is found in GH. It has the fat reducing component of HGH without the side effects.

This peptide was developed to help the body burn fat by regulating the body’s metabolism and stimulating the body’s natural fat burning process. It triggers the release of fat from obese fat cells and decreases the growth of new fat that surrounds the fat cells.

Research has shown that is reduces body weight, increases fat oxidation and increases lipolysis in obese animals (5).

How does tesofensine work?

Tesofensine works by inhibiting the neurotransmitters; noradrenalin, dopamine and serotonin in the brain from being reabsorbed in the body. The body responds by suppressing hunger.

Subsequently patients have smaller meals and are less likely to snack. It also appears to affect the pleasure sensation of food consumption by modulating the action of dopamine on a particular sector of the brain (5).


The market for peptides is expanding with multiple companies producing peptides related products. With this expansion there is always the question of whether a supplement is safe or not.

Collagen peptides are safe however there are potential side effects with the common being gastrointestinal symptoms and rashes if taken topically.

The safety of using GSHs over a short and long term period is unknown. The side effects are more serious than collagen peptides and include increased appetite, elevated blood sugar levels, fluid retention and a risk of contamination if non- sterile needles are used (3).

The safety of MOTS-c has not been established yet, more research is needed. AOD9604 is approved by the FDA and has obtained Human GRAS status and does not have harmful effects on blood sugar levels.

Tesofensine has been reported to have a good safety profile however there was an increased number of side effects observed in a group of participants who had a higher dosage (5).

There is limited research on the safety of the use of peptides and more research is needed. Collagen peptides are not yet approved by the FDA and there are limited GSH peptide supplements that have been approved by the FDA with some GSH peptides currently banned by the World Anti-Doping Agency (3).

When buying a peptide supplement, it is important to buy from a reputable source with quality ingredients.

Are they legit?

The research around peptides is increasing rapidly however more research is needed. The evidence for collagen supplements with reducing aging lines and relieving joint pain is promising however there is limited research with collagen and improving muscle growth and bone density (1).

Research suggests that GSH increases the release of HGH or IGF-1 however there are limited studies in analyzing the body composition before and after the use of peptides (3).

There is currently research being conducted over the use of MOTS-c and AOD965 in weight loss (5).

If you are considering taking a peptide supplement, do your research- we have a range of articles regarding the different peptides and how they work, as well as reviews of various peptides, consult with your healthcare provider, and choose a reputable source.

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2. https://www.medicalnewstoday.com/articles/326701#side-effects
3. https://www.healthline.com/nutrition/peptides-for-bodybuilding#bottom-line
5. https://doctorpaulvin.com/blog/7-game-changing-peptides-for-fat-loss/


Michelle Hawksworth

Michelle Hawksworth | Writer

Michelle Hawksworth is a South African Registered Dietitian and yoga teacher with a passion for running, wellness, and supplements. She blends traditional nutrition and physical activity principles with a holistic approach to health, and provides evidence-based information to her clients. Michelle is dedicated to empowering individuals to take control of their health and make sustainable changes. She is an inspiration to others through her work and dedication to health and wellness.

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Christina Hotchkiss
Christina Hotchkiss
1 year ago

I’m interested in MOTS-C. How would I cycle safely? Daily? How long & typical dose for fat loss & anti aging. Thanks!

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