This article explains the nature of peptides, their functions within the body, and their potential to support sustainable weight loss. It will also highlight the potential side effects and other safety aspects.
What Are Peptides?
Peptides are short chains of amino acids, typically ranging from 2 to 50. Serving as the building blocks of proteins, they act as messengers, transmitting signals throughout the body. In clinical practice, peptide therapy involves the use of laboratory-made peptides to mimic or enhance natural bodily functions. While some peptides, such as GLP-1 receptor agonists (e.g., semaglutide), have demonstrated weight-loss benefits, they are typically prescription medications developed for diabetes or obesity management, rather than general wellness treatments.
Do Peptides Really Help You Lose Weight?
Recent evidence shows that GLP-1 receptor agonists can help people lose weight by:
- stimulating the release of the hormone insulin, which helps regulate blood sugar
- delaying stomach emptying (gastric emptying)
- increasing fullness (satiety)
- reducing appetite
- alleviating food cravings
Specific peptides, such as GLP-1 receptor agonists like semaglutide (Ozempic, Wegovy), liraglutide (Saxenda), and tirzepatide (Mounjaro), have been shown in clinical studies to aid individuals who are overweight or obese in losing weight or managing related metabolic conditions. These peptides work by mimicking natural hormones that regulate appetite and glucose metabolism, specifically incretin hormones naturally produced by the gut in response to eating. This leads to a reduction in the number of calories consumed, which aids in weight loss over time.
Frontiers in Endocrinology confirms that GLP-1 receptor agonists can improve metabolic markers and fat oxidation, but only when combined with dietary and behavioral interventions. It's important to note that not everyone responds to peptide medications in the same way, and they do not guarantee weight loss. Clinical trials often include intensive lifestyle support (nutritionists, exercise programs), which may not reflect real-world conditions. These drugs are not a substitute for behavior change, and discontinuing them often leads to weight regain.
Read also: Is a liquid diet right for you?
The Best Peptides for Weight Loss
The best peptides for weight loss are those approved by the Food and Drug Administration (FDA). Examples include:
Semaglutide
As a 2024 review explains, semaglutide is a GLP-1 receptor agonist. There are three separate semaglutide brands:
- Rybelsus
- Ozempic
- Wegovy
Of these, the only drug to receive FDA approval as a weight loss aid is Wegovy.
Wegovy injection is FDA approved as a long-term weight loss aid for the following individuals:
- adults with obesity, alongside a reduced-calorie diet, and increased physical activity
- adults with overweight, and at least one weight-related condition, such as:
- hypertension
- type 2 diabetes
- dyslipidemia
- children ages 12 years or above with a body mass index (BMI) at or above the 95th percentile for their age and sex
A 2021 study investigated the effectiveness of semaglutide as a weight loss aid in 1,961 people with overweight or obesity. Over 68 weeks, each participant received a once-weekly dose of either 2.4 milligrams (mg) of subcutaneous semaglutide or placebo, alongside lifestyle interventions.
Read also: Explore the pros and cons of liquid diets
Individuals in the semaglutide treatment group lost, on average, 14.9% of their body weight compared to baseline. Individuals in the placebo group lost, on average, just 2.4% of their body weight compared to baseline. The researchers also compared the percentage of individuals in each group who achieved weight reductions of 5% or more.
Liraglutide
Liraglutide is another type of GLP-1 receptor agonist. As a 2024 review explains, the FDA approved liraglutide in 2014 for the treatment of adult obesity, and studies have also shown the drug to be effective in children ages 12 to 18 years.
Liraglutide goes by the following brand names:
- Saxenda
- Victoza
adults with obesityadults with overweight and at least one weight-related health condition
A 2017 review and meta-analysis of five randomized controlled trials (RCTs) investigated the safety and effectiveness of liraglutide for weight management. The review found that the number of individuals achieving a weight loss of 5% or 10% was significantly higher in the liraglutide group compared to the placebo group.
Read also: Risks of Liquid Diets
Tirzepatide
Tirzepatide activates GLP-1 receptors and glucose-dependent insulinotropic polypeptide (GIP), an intestinal hormone that plays a role in insulin secretion and lipid metabolism.
In 2023, the FDA approved a tirzepatide injection with the brand name Zepbound for weight loss in the following individuals alongside a reduced calorie diet and increased physical activity:
- adults with obesity
- adults with overweight and at least one weight-related condition
Zepbound is both a GLP-1 receptor agonist and a GIP receptor agonist, so it helps reduce appetite and food intake. It is a subcutaneous injection that a person administers once a week.
The recommended starting dose is 2.5 mg. After the first 4 weeks, a person can gradually increase the dosage in 2.5 mg increments over the course of 4 to 20 weeks until they reach their target weekly dosage of 5 mg, 10 mg, or 15 mg.
A 2024 study investigated the effect of once-weekly subcutaneous tirzepatide on weight loss management in adults with overweight or obesity. At 36 weeks, the 670 adults experienced an average weight reduction of 20.9%. From this time point, researchers separated the participants into two groups: a treatment group and a control group. At 52 weeks, the group continuing tirzepatide experienced an additional 5.5% weight reduction, while the group who switched to the placebo regained 14% of their body weight.
Other Peptides
Several peptides can support fat loss and help you reach your ideal weight. Each of these peptides works differently to target different areas of the body. Semaglutide decreases insulin resistance and is a powerful anti-inflammatory. BPC 157 helps promote muscle growth, CJC-1295 aids in fat loss and increases the amount of growth hormone released from the pituitary gland.
GLP-1 (glucagon-like peptide-1) agonists are a popular class of peptides for weight loss. They reduce appetite, improve blood sugar control, and enhance metabolic health. A newer peptide, Retatrutide, is a triple receptor agonist in development. Growth hormone releasing peptides (GHRPs) stimulate the release of growth hormone, supporting metabolism, fat loss, and muscle maintenance. AOD-9604 is a fragment of human growth hormone designed to burn fat without affecting blood sugar levels.
Who Should (and Shouldn't) Use Peptides for Weight Loss?
Peptide-based medications are not intended for general or cosmetic weight loss. They are typically appropriate for adults who meet one of the following medical conditions:
- Body Mass Index (BMI) is 30 or higher, without the need for additional health conditions. Chronic diseases like type 2 diabetes, cancers, and heart problems are more likely to happen to these people.
- FDA's prescribing guidelines for GLP-1 receptor agonists, such as Wegovy and Saxenda.
These medications are not suitable for everyone. Inappropriate use can result in serious side effects or ineffective outcomes.
- Pregnant or Breastfeeding Women: GLP-1 receptor agonists are not safe for use during pregnancy or lactation. Patients who become pregnant while on these medications are advised to stop immediately.
- These medications are not intended for losing a few vanity pounds. Using peptides without meeting the clinical criteria increases the risk of complications and frequently leads to weight regain upon discontinuation.
- Serious health risks. Non-FDA-approved products may be contaminated, underdosed, or misbranded.
Peptides for weight loss should be used only by those who meet specific medical criteria, under the guidance of a healthcare provider. They are not appropriate for short-term, self-managed, or cosmetic weight loss goals, and they carry real risks for individuals with certain pre-existing conditions. Proper screening, diagnosis, and ongoing monitoring are crucial for ensuring the safe and effective use of this medication.
Peptides Are Not Standalone Fat-Burning Solutions
Peptides are often marketed online as shortcuts to rapid fat loss, but these claims are misleading. Many people assume that starting a peptide injection will lead to visible fat loss without requiring any lifestyle adjustments.
Some peptides help promote weight loss by helping to regulate blood sugar levels, metabolism, and appetite. However, these effects are secondary and occur only when the patient is already engaging in other weight management strategies. Peptides cannot replace the foundational work of structured, personalized health planning.
Safety Considerations and Potential Side Effects
Using versions of GLP-1 receptor agonists that are not FDA-approved can be unsafe. They could contain harmful ingredients and too much or too little of the active ingredient. They may not contain any of the active ingredients at all. Counterfeit products are available online that may increase the risk of adverse effects.
According to the NIDDK, peptides and other weight loss medications may sometimes cause side effects that outweigh the benefits of weight loss. For this reason, people should only take weight loss medications to improve their health, never for cosmetic reasons alone.
Before prescribing peptides for weight loss, doctors must consider certain precautions.
Peptides for weight loss may delay gastric emptying, which can reduce the effectiveness of oral medications.
The FDA cautions that both Wegovy and Zepbound may not be suitable for use during pregnancy, as these medications may harm the fetus. The FDA recommends that males and females of reproductive age discontinue using Wegovy at least 2 months before a planned pregnancy, as the drug can remain in the system for several weeks.
With Zepbound, the FDA recommends that females using oral contraceptives switch to a non-oral contraceptive method or add barrier contraception for 4 weeks after the initial Zepbound dose, and for 4 weeks after each dose increase.
Peptides for weight loss may also not be suitable for people with a personal or family history of certain conditions, including:
- medullary thyroid cancer
- multiple endocrine neoplasia type 2
- hypersensitivity to the active ingredient, or any other ingredient in the medication
The chart below shows the possible side effects of Wegovy, Saxenda, and Zepbound:
Consulting a Healthcare Professional
A person should contact a doctor if they want to discuss issues with their weight or require advice on appropriate weight loss methods and treatments. A person should also contact a doctor if they are taking a weight loss medication and begin to experience side effects. Depending on the nature and severity of the side effects, the doctor may recommend adjusting the medication dosage or switching to an alternative medication or weight loss method. However, a person should not stop taking a medication unless their doctor advises them that it is safe to do so.
Peptides in Bodybuilding
Supplement companies often claim peptides can amplify muscle gain and facilitate fat loss. But few studies have explored the impact of peptides on bodybuilding, and some are banned in professional sports.
Peptides are a popular performance-enhancing aid in the bodybuilding community. Theyâre short chains of amino acids, which are small molecules that are the building blocks of peptides and proteins. Peptides exist naturally in your body, but you can also find them in animal or plant sources of protein. Manufacturers can isolate these peptides or make them by combining individual amino acids.
You can purchase peptide supplements as a powder that you can mix with a liquid and consume orally. Alternatively, you can find them in injectable form. Some people view peptides as a more natural alternative to anabolic steroids, praising them for their ability to boost muscle mass, promote fat loss, and help bodybuilders maximize their workout results.
However, scientific research on these purported benefits is limited and mixed. Keep reading to learn more about the possible benefits and risks of using peptides for bodybuilding.
Peptides can have structures similar to those of certain hormones and signaling compounds in the body, allowing them to engage with and activate multiple receptors throughout the body, thereby influencing various bodily processes.
Depending on their sequence and composition, certain peptides may help prevent blood clots, boost the immune system, protect cells against damage, and reduce cholesterol, inflammation, and blood pressure.
Specific peptides may also help boost the release of hormones known to stimulate muscle growth, body fat loss, and exercise performance and recovery. This makes them particularly appealing to bodybuilders seeking to maximize their training results.
Bodybuilders are typically interested in changing their body composition as quickly and efficiently as possible. Research suggests that certain peptides may help them achieve these goals.
HGH is a hormone secreted by the pituitary gland. It may help enhance muscle growth and indirectly promote body fat loss by stimulating the liver to release insulin-like growth factor-1 (IGF-1). In turn, IGF-1 stimulates muscle protein synthesis and promotes muscle growth.
Back in the 1980s, HGH was a popular performance-enhancing drug among various recreational and professional athletes, including bodybuilders. But, due to safety concerns, regulating bodies like the International Olympic Committee banned the off-label use of HGH from 1989 onward. Some people claim that GHSs offer many of the same benefits as HGH with fewer side effects. This may explain their popularity as an alternative to HGH among bodybuilders.
While some research suggests that GHS increases the release of HGH or IGF-1 in humans, more studies are needed to determine whether taking GHS actually leads to significant changes in body composition, exercise performance, or recovery.
Whatâs more, no studies have examined the effect of GHSs on well-trained individuals, so scientists currently donât know which muscle groups peptides may affect most, or which workouts they might be best suited for.
Bodybuilders may be particularly interested in GHS peptides. The most popular GHSs for bodybuilding include:
- growth-hormone releasing hormones, such as sermorelin, tesamorelin, CJC-1293, and CJC-1295
- ghrelin and compounds mimicking its actions, such as lenomorelin, anamorelin, ipamorelin, macimorelin, and tabimorelin
- growth hormone-releasing peptides (GHRPs), such as alexamorelin, GHRP-1, GHRP-2, GHRP-3, GHRP-4, GHRP-5, GHRP-6, and hexarelin
Each of these peptides may stimulate the production and release of HGH, although they do so in slightly different ways. Manufacturers often promote each category for slightly different purposes. However, itâs important to note that no studies to date have investigated the effects of GHSs in bodybuilders or other highly trained individuals.
Therefore, indications and recommended dosages are typically based on anecdotal evidence rather than science. The safety of using GHSs over the short and long term is unknown. Studies investigating their safety have been limited in size and duration. Therefore, scientists need to conduct further research to investigate the safety of GHS.