Just a few years ago, the idea of a drug that could reduce body weight by a fifth while also protecting the heart and kidneys sounded like science fiction. Today it is reality. Drugs from the GLP-1 class – semaglutide (Ozempic, Wegovy) and tirzepatide – are genuinely changing the lives of people with obesity and type 2 diabetes. They are not drugs "for the lazy", as is sometimes said. They are tools that act on the biology of hunger and metabolism. To work well, however, they need to be understood.
How to read the numbers: Today’s average = common in today’s population – not a target or optimum · Risk = what to watch out for
with semaglutide over 68 weeks
with tirzepatide 15 mg over 72 weeks
and cardiovascular death in SELECT
How GLP-1 drugs work
GLP-1 is a hormone released by gut cells after a meal. It works as a "we have eaten" signal. It helps the pancreas release insulin exactly when glucose is rising, suppresses glucagon, which raises blood sugar, slows stomach emptying and acts directly on the hunger and satiety centres in the brain. Natural GLP-1 is broken down within minutes. Modern drugs are modified to last in the blood for several days, so one injection a week is enough.
Tirzepatide goes a step further. It activates two receptors at once – GLP-1 and GIP, another gut hormone involved in processing nutrients. In trials, the result is an even greater weight reduction. People on these drugs most often describe how the "food noise" in their head suddenly goes quiet. Constant thoughts about food, cravings and the urge to keep eating fade. For many, it is the first time in their life they feel in control of food.
What the large trials showed
The evidence here is exceptionally strong. These are large randomized trials with thousands of participants, published in the most prestigious medical journals.
- Obesity – in the STEP 1 trial, adults with overweight or obesity lost an average of 14.9% of their body weight on semaglutide 2.4 mg over 68 weeks, compared with 2.4% on placebo. Half of the participants on the drug lost 15% or more.
- Tirzepatide – in the SURMOUNT-1 trial, the highest dose achieved an average reduction of 20.9% over 72 weeks. More than half of the people on the higher doses lost at least a fifth of their body weight.
- Heart and blood vessels – the SELECT trial followed more than 17,600 people with overweight and cardiovascular disease who did not have diabetes. Semaglutide reduced the risk of heart attack, stroke or cardiovascular death by 20%.
- Kidneys – in the FLOW trial in people with type 2 diabetes and chronic kidney disease, semaglutide reduced the risk of major kidney worsening or death from kidney and cardiovascular causes by 24%.
This is crucial: GLP-1 drugs are not just cosmetics for the scales. In trials they protect the heart, blood vessels and kidneys. Medicine rarely gets a tool with such a broad reach.
Side effects and why this is a prescription drug
The most common problems are digestive: nausea, vomiting, diarrhoea or constipation, and a feeling of a full stomach. They usually appear at the start of treatment and when the dose is increased, and they gradually subside. That is exactly why the dose is increased slowly, step by step. In STEP 1, 4.5% of people on semaglutide stopped treatment because of digestive problems, compared with 0.8% on placebo. Gallbladder problems or pancreatitis occur less often, and the drugs are not suitable for everyone – for example during pregnancy or with certain thyroid cancers in the family.
GLP-1 drugs are prescription drugs, and that is how it should be. A doctor assesses whether you really need them, rules out contraindications, sets a gradual dosing schedule and monitors how you respond to treatment. Buying "semaglutide" online or from unverified sources is a gamble – you never know what is in the vial or at what dose. Never adjust the dose on your own.
Another important point: the drug works as long as you take it. In the STEP 1 extension, people who stopped semaglutide regained about two thirds of the weight they had lost within a year. Obesity is a chronic disease and treatment is usually long-term. The key is to use the time on the drug to build habits that will stay with you.
Muscle loss: the silent tax of rapid weight loss
With any major weight loss, the body loses not only fat but also part of its lean mass – muscle, water and other tissue. With GLP-1 drugs this is especially relevant, because people eat much less. A 2024 review reports that in some studies lean mass made up 40 to 60% of total weight lost, in others around 15% or less. The differences depend on the measurement method, age and lifestyle.
Why does it matter? Muscle is a metabolic organ. It burns glucose, protects against falls and frailty in old age, and is one of the strongest markers of a long and healthy life. Losing twenty kilos while losing a large part of your muscle is not a good deal. The good news is that you can protect your muscle during treatment.
Put protein first at every meal – when appetite is low, eat meat, fish, eggs, cottage cheese or legumes first and only then the side dish. Do strength training two to three times a week, full body, with gradually increasing load. Add daily movement and walking. Drink enough fluids and track how your waist and strength change, not just the number on the scale. If possible, have your body composition measured.
Peptides: BPC-157 and other community heroes
Technically, GLP-1 drugs are also peptides – short chains of amino acids. In the biohacking community, however, the word "peptides" usually means a different group of substances: BPC-157, TB-500, growth hormone-supporting peptides such as ipamorelin or CJC-1295, and many others. The community credits them with faster healing of tendons and ligaments, better sleep, recovery or gut protection. BPC-157 has earned the nickname "Wolverine peptide".
I know many people who have had good experiences with them. But I have to be fair: the difference in the quality of evidence compared with GLP-1 drugs is enormous. A 2025 systematic review found 36 studies on BPC-157 in orthopaedics and sports medicine, 35 of them in animals and in the laboratory, and only one small clinical study in humans. The substance is not approved as a medicine and is banned in sport. Products are often sold labelled "for research only", so nobody guarantees their purity or content.
If you are considering peptides, do not do it on your own. They belong in the hands of a doctor who knows their risks, and they will never replace the basics – sleep, diet, exercise and evidence-based treatment.
- Strong evidence Semaglutide and tirzepatide markedly reduce weight in obesity and improve control of type 2 diabetes; semaglutide reduces the risk of cardiovascular events (SELECT) and kidney worsening (FLOW).
- Moderate evidence Part of the weight lost is lean mass; protein and strength training probably help protect it. After stopping the drug, most of the weight returns.
- Weak evidence BPC-157 and similar peptides for healing and recovery – almost exclusively animal studies, with only isolated small studies in humans.
- No evidence "Semaglutide" from unverified online sources as a safe alternative to treatment under medical supervision.
Conclusion
GLP-1 drugs are a real breakthrough and help millions of people. But they belong in the hands of a doctor, with gradual dosing and a long-term plan. If you take them, think about your muscle: protein, strength training and movement turn weight loss into a real gain in health. Peptides from the biohacking community are interesting, but for now they rest mainly on experience and animal studies. Use the power of science where it is solid, and be careful where it is only emerging.
