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Obesity rates are soaring across the United States and the world, with a majority of Americans now overweight or obese. With obesity now widely acknowledged as a pandemic, there’s significant interest in novel therapies for shedding those pounds—including peptide-based weight loss injections.
Over the past several years, researchers and clinicians have realized that a class of peptides known as glucagon-like peptide-1 (GLP-1) receptor agonists could have powerful effects on weight. These compounds help reduce hunger and regulate blood sugar levels, making it easier for people with obesity to stick with a reduced-calorie diet.
The result is rapid weight loss and better health, making GLP-1 receptor agonists a valuable tool in the ongoing battle against climbing obesity and chronic disease rates.
Three of the most powerful, well-known, and thoroughly-researched weight loss peptides include:
Here’s our review of these three peptides for weight loss, along with our top recommendations of online sources that ship all three to U.S. based researchers.
Here are the top three peptides for weight reduction and fat loss:
Before discussing peptide-based weight loss therapies, let’s first define the term “peptides.”
In the most basic terms, peptides are composed of amino acids or the “building blocks” of protein. Peptides are short chains of amino acids consisting of 50 amino acids or less, while proteins are made of 51 or more amino acids.
Peptides have a variety of uses in the body, and the body synthesizes many of them naturally as part of its biochemical processes. They can also be broken down from food and dietary supplements and used by the body.
Peptides are a large and diverse class of compounds, and many powerful medications are peptide-based.
Weight loss injections are now soaring in popularity, like semaglutide, liraglutide, and tirzepatide, are all peptides. These are unique types of peptides known as glucagon-like peptide-1 (GLP-1) receptor agonists (though tirzepatide happens to be a dual GLP-1/GIP agonist, as discussed below).
GLP-1 is a hormone that helps regulate appetite and blood glucose levels. It’s produced in the intestinal cells and is typically activated in response to eating. GLP-1 stimulates the secretion of insulin, a hormone that shuttles excess sugar from the blood. It also slows down gastric transit, the pace at which food moves through the digestive tract .
GLP-1 receptor agonists activate the glucagon-like peptide-1 receptors, stimulating them beyond the level of a typical meal. For weight loss, this does two key things:
First, it increases satiety. Slowed digestion means that feeling fuller for longer, making it easier to slash calories by eating less [2, 3].
Also, GLP-1 activation stimulates insulin secretion. Many obese patients are also insulin resistant, so their bodies “ignore” insulin. However, GLP-1 receptor agonists can increase the body’s natural insulin production so that the body can “hear” these signals .
Together, these two effects lead to weight loss. When paired with a low-calorie diet and exercise, weight loss can be rapid and dramatic.
Although there are some slight differences between the many GLP-1 receptor agonists available, they all work in essentially the same way.
Here’s a quick rundown of the best injections for weight loss, including how they work, a review of the most recent research, and a summary of their potential side effects and risks.
Tirzepatide is a GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist. In May 2022, it was approved by the United States Food and Drug Administration (FDA) for use as a type 2 diabetes treatment available under the brand name Mounjaro.
It is also used off-label to promote weight loss in people with overweight or obesity and is currently in clinical trials for this purpose.
As a GLP-1 and GIP receptor agonist, tirzepatide works by slowing down gastric motility and increasing insulin secretion, ultimately resulting in increased satiety and better blood sugar control. This benefit for people with type 2 diabetes often results in weight loss, especially when paired with a balanced diet and moderate exercise.
The results of phase 3 clinical trial on tirzepatide for obesity in non-diabetics was published in The New England Journal of Medicine in July 2022. This study included over 2,500 participants with a body mass index (BMI) of 30 or more, or 27 or more with at least one weight-related complication. After 72 weeks, the placebo group had lost an average of 3.1% of their body weight, while the tirzepatide groups had lost an average of 15%-20.9% of their body weight .
Tirzepatide commonly causes gastrointestinal side effects like nausea, vomiting, and diarrhea. It may also be associated with an increased risk of thyroid tumors or thyroid cancer, as this is a known complication of GLP-1 receptor agonists in rat studies. Note, however, that this effect has never been observed in humans .
Tirzepatide is a once-weekly subcutaneous injection that can be taken long-term. The dose must be gradually titrated up to the optimal dosage to prevent severe gastrointestinal side effects.
Clinical research subjects concurrently on blood glucose-lowering medications like insulin or metformin should be carefully monitored as tirzepatide may increase their risk of hypoglycemia.
Semaglutide is perhaps the most well-known weight loss peptide in the U.S. and globally. It’s currently FDA-approved for both weight loss and type 2 diabetes management.
In 2017, it was approved for type 2 diabetes under the brand name Ozempic. In 2019, an oral version sold under the brand name Rybelsus was approved. Finally, in 2021, a high-dose version was approved for weight loss and is currently sold under the brand name Wegovy.
Semaglutide appears to be one of the most powerful of the GLP-1 receptor agonists and has been found to promote an average weight loss of 15% of body weight after 68 weeks of administration. It works by reducing appetite by slowing down the digestion process, and it also increases insulin levels.
In one meta-analysis of four randomized controlled trials including over 3,600 nondiabetic obese, researchers noted an average weight loss of 11.85%. However, the review authors also found that semaglutide was associated with a notable risk of gastrointestinal side effects .
In an analysis comparing tirzepatide and semaglutide, researchers found that semaglutide was associated with a slightly lower rate of weight loss and a slightly higher rate of gastrointestinal side effects compared to tirzepatide .
Like tirzepatide, semaglutide may cause nausea, vomiting, or diarrhea. Subjects with a history of thyroid cancer should also be excluded from semaglutide clinical research, since the peptide also increases the risk of thyroid cancer in rats. As with the other GLP-1 receptor agonists and tirzepatide, this effect has not been observed in humans .
Semaglutide is also a once-weekly subcutaneous injection, although there is an oral tablet version available (Rybelsus) for diabetics by prescription. Women who are pregnant or breastfeeding should avoid participating in semaglutide research.
Liraglutide is another GLP-1 receptor agonist that has a number of similarities to both semaglutide and tirzepatide. It was first approved for type 2 diabetes in the U.S. in 2010, and then for weight loss in 2014. Additionally, it was approved for weight loss in adolescents in 2020.
Like semaglutide, it works by activating GLP-1, which slows down the transit time of food in the digestive tract and stimulates insulin secretion. This two-pronged mechanism of action increases satiety, reduces appetite, levels out blood sugar levels, and reduces food cravings—all of which can lead to weight loss.
Liraglutide and other GLP-1 receptor agonists are particularly helpful for weight loss when paired with a healthy diet and exercise. While liraglutide may not be as effective for weight loss as semaglutide or tirzepatide, it also appears to have fewer side effects. It can also help to improve heart health in patients with type 2 diabetes .
In a 2022 trial published in JAMA, researchers compared once-daily liraglutide with once-weekly semaglutide. The semaglutide group lost over twice as much weight as the liraglutide group, although the participants using liraglutide still lost an average of 6.4% of their body weight .
A key drawback of liraglutide is that it requires daily subcutaneous injections. This limits its convenience in comparison to semaglutide and tirzepatide, which are both once weekly. Additionally, daily injections may make the side effects of injections—like pain, swelling, or bruising at the injection site—a more commonplace occurrence.
As is the case with other GLP-1 receptor agonists, liraglutide frequently causes mild digestive side effects like vomiting, nausea, and diarrhea. Additionally, liraglutide may also increase the risk of thyroid gland tumors or thyroid cancer, an effect that has been noted in animal studies, but not observed in clinical studies. Still, subjects with a history of thyroid cancer or thyroid-related conditions like multiple endocrine neoplasia type 2 should not participate in research on liraglutide .
Tirzepatide, semaglutide, and liraglutide are all related peptides. They are all GLP-1 receptor agonists with similar mechanisms of action and safety profiles. All three appear to be safe for most weight loss subjects if administered correctly. In fact, they have all been approved by the U.S. Food and Drug Administration (FDA) and are available under various trade names.
All three can support both weight loss and blood sugar management. However, based on user experiences and existing research, semaglutide and tirzepatide appear to be more effective for weight loss than liraglutide. Semaglutide is also currently FDA-approved for weight loss, and tirzepatide is poised for approval for weight loss in the near future (late 2023).
These peptides likewise have similar side effects and contraindications. The most common side effects of each are gastrointestinal: nausea, vomiting, and diarrhea. Nausea is by far the most commonly reported side effect, affecting up to half of subjects who undergo GLP-1 receptor agonist peptide therapy .
Additionally, all three peptides carry a potential risk for thyroid cancer and the development of thyroid tumors. This effect has been noted in preclinical animal research but not observed in humans.
Finally, tirzepatide, semaglutide, and liraglutide are all available through reputable research peptide vendors. The total cost of research can vary significantly based on vendor, dosage, and other factors. Read on for information on where to source research-grade versions of all three online.
There are several online vendors who list weight loss peptides for research purposes. However, not all vendors are created equally.
Reputable vendors provide high-quality peptides that have been lab-tested for purity, fast worldwide shipping, and several payment options. Here are our three favorite peptide vendors:
Peptide Sciences offers a comprehensive catalog of research peptides, all made in the U.S. and at least 99% pure. This vendor offers tirzepatide, semaglutide, and liraglutide for research purposes, and all compounds are third-party tested by independent labs to ensure quality.
Additionally, Peptide Sciences offers free domestic shipping on orders over $200. They also regularly run promotions, including discounts on large orders, free bacteriostatic water, and free shipping. However, they currently do not offer worldwide shipping and only ship within the U.S., so overseas-based scientists should check elsewhere.
Core Peptides also offers tirzepatide, semaglutide, and liraglutide for research. Their peptides are tested for purity, and they offer worldwide shipping. For U.S.-based orders, they offer free shipping over $200. Their products are also made in the U.S, but at this time the vendor accepts payments only via credit card.
Limitless Life is a vendor that provides a variety of research peptides as well as nootropics, or brain-enhancing compounds. While they do not currently offer liraglutide, semaglutide, or tirzepatide, all three compounds are expected to be in stock soon. Sign up for their VIP mailing list through the above link to stay informed on availability and for price breaks.
Visit any one of these top vendors today to source top-quality tirzepatide, semaglutide, liraglutide, or other peptides for weight loss.
Weight loss injections can vary significantly in cost depending on the vendor, the peptide purchased, the size and concentration of the vials, and the form.
When purchasing peptides, do not forget to account for the costs of shipping and necessary laboratory supplies — such as bacteriostatic water, needles, syringes, and alcohol pads.
Researchers may also be able to access bulk-purchasing discounts for large orders.
For example, at our preferred vendor Peptide Sciences, 30mg liraglutide costs $485, 3mg semaglutide costs $120, and 5mg tirzepatide costs $160.
While liraglutide is significantly less expensive per milligram than semaglutide or tirzepatide, it requires once-daily dosing unlike the latter two.
Remember that prices will vary between vendors, and these prices do not include any available promotions or bulk discounts.
Research peptides for weight loss typically arrive in a powdered form in vials. Scientists will need a few supplies to properly reconstitute and administer these peptides.
The first is bacteriostatic water. This is a sterile solution that inhibits the growth of bacteria thanks to the addition of 0.9% benzyl alcohol. It is used instead of regular water to reconstitute injectable peptides and other injectable compounds to drastically reduce the risk of introducing potentially harmful bacteria to the bloodstream during the injection process.
Peptide researchers will also need needles, syringes, and alcohol prep pads. Luckily we have found a reliable retailer of laboratory supplies that offers kits designed specifically with peptide research in mind: BacteriostaticWater.org
To reconstitute a peptide for injection, first, sanitize all supplies and your hands using alcohol prep pads. Using the needle and syringe, draw up the directed amount of bacteriostatic water from its vial then insert it into the vial of peptide. Then, swirl the vial until the peptide is completely dissolved into the solution. Avoid shaking the vial.
To administer the peptide solution, draw the correct dosage into a new syringe, then depress the plunger to remove air bubbles.
Next, pinch the skin where the injection will be placed to make it firm. Weight loss peptides are often injected into the stomach, but may also be injected into the thighs or upper arms. Participants may also want to rotate injection sites.
Insert the needle into the skin, and then slowly depress the plunger to administer the peptide. Remove the needle and syringe and dispose of it in an appropriate sharps container.
Because weight loss injections are subcutaneous — or just below the skin—they are relatively easy and painless for most to administer.
Clinicians and researchers alike have observed many people finding great success with weight loss peptides. Before and after pictures and stories online note losses of up to fifty pounds in a number of months. Many patients who have struggled to control their weight throughout their life have found weight loss success through semaglutide, tirzepatide, or liraglutide.
Still, there are a number of factors that may influence the effectiveness of these peptides from individual to individual.
First, starting weight is a key consideration. Those who are larger often lose more weight at a more rapid pace than those who need to lose a small amount of weight.
Next, diet and lifestyle factors can affect the rate of weight loss in those given peptides like tirzepatide, semaglutide, or liraglutide. Calories still matter, so strictly following a reduced-calorie diet or engaging in calorie-burning exercises can shed weight faster.
Finally, dosage and adherence to a well-designed peptide protocol will have a huge impact on weight loss. Most weight loss peptides require a weekly injection, and those compounds backed by extensive research already have established dosing protocols.
Clinical studies and case reports detail incredible results from weight loss peptides. These are more reliable than online anecdotes since they are published in peer-reviewed scientific journals. In a case report published in Cureus, GLP-1 receptor agonists led to a weight loss of over 100 pounds in a morbidly obese person with a genetic condition that caused extreme obesity and compulsive eating .
GLP-1 receptor agonists have also been noted to be extremely successful in other cases of morbid obesity, including in one woman with a body mass index (BMI) of over 100 and a weight of nearly 700 pounds. Combined with an extremely low-calorie diet, peptide therapy promoted a weight loss of 174 pounds in just 31 weeks .
There’s been a flurry of research on weight loss peptides over the past decade, and the potential effects of these peptides began to be observed and more understood.
Research is still ongoing at a blistering pace. There’s huge interest in weight loss peptides and weight loss medications from the scientific and medical communities as well as society at large.
One particular advancement of interest is the development of new, more convenient and efficient delivery methods. Injections can be burdensome, so delivery methods including oral, transdermal, or nasal sprays show promise.
As obesity and diabetes rates continue to climb, a multi-pronged approach will be necessary. Just like weight loss surgery or strict diet programs, peptides for weight loss may not be right for everyone—but they will be right for some.
Additional breakthroughs could help stem the tide of obesity and diabetes as we work towards making major changes to our food system to help reduce the incidence of these conditions at the source.
Semaglutide, tirzepatide, and lireglutide are peptides that can help people with obesity and type 2 diabetes lose weight, manage their blood sugar levels, and drastically improve their health.
All work at the GLP-1 receptor to slow down digestion and increase insulin production. Tirzepatide additionally acts on the GIP receptor to trigger a broad range of physiological effects.
While all three may cause digestive side effects, the research community has reported great success in applying these peptides for weight loss, with high-quality trials and case studies showing fantastic results.
As interest in peptides for weight loss grows, there will be more opportunities for researchers to study GLP-1 receptor agonists and develop new compounds.
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