Are Ozempic and similar medications dangerous? What does the science actually say?

What exactly are these new weight-loss medications everyone’s talking about?

Weight-loss medications aren’t some newly discovered drugs with unknown mechanisms. GLP-1 agonists have actually been used for over 15 years, primarily to treat type 2 diabetes. They work by mimicking the natural hormone GLP-1 in our body, which slows down how quickly the stomach empties, helps you feel full longer, and reduces appetite. At the same time, they improve blood sugar control by increasing insulin release and lowering glucagon levels.

This combination—food staying in the stomach longer and a reduced desire to eat (including fewer cravings)—is what leads to relatively faster weight loss.

What was used for weight loss before, and how did these new medications come into the picture?

Before GLP-1 agonists, obesity treatment was mainly based on diet, physical activity, and older medications like orlistat, which had limited effectiveness and, unfortunately, frequent side effects. It’s important to point out that Ozempic is approved for treating type 2 diabetes and is covered by insurance only under specific criteria—typically in patients whose blood sugar (HbA1c) remains poorly controlled despite existing therapy, such as metformin.

Medications specifically approved for weight loss came later. In practice, this includes liraglutide (daily injections), as well as semaglutide and the newer tirzepatide (both weekly injections). Tirzepatide targets both GLP-1 and GIP receptors and, as seen in clinical use, tends to lead to faster weight loss—though often with more side effects as well.

Metabolic effects and benefits

GLP-1 medications have multiple effects, with the main benefits including weight loss of about 10–20% of body weight (depending on the drug and dose), improved insulin resistance, better lipid profiles, and a reduction in overall cardiovascular risk.

Their effects on blood lipids are mostly indirect—through weight loss and improved insulin sensitivity—but they also have some direct metabolic actions. They help lower triglycerides by reducing post-meal fat levels (thanks to slower gastric emptying and reduced food intake), and they can lower LDL (“bad cholesterol”) as weight loss leads to decreased production of LDL in the liver. However, the largest impact comes from the loss of visceral fat—the deeper abdominal fat—which reduces inflammation and improves the overall metabolic profile.

Cardiovascular outcome studies have also shown a reduced risk of heart attack and stroke in people with diabetes. A common counterargument is that we don’t fully know how these mechanisms apply to otherwise healthy individuals. But today, about 1 in 10 people has diabetes, while 25–40% have insulin resistance, and 30–40% have abnormal lipid levels. Early signs of atherosclerosis have even been found in infants over the past decades—meaning most metabolic problems begin long before diabetes develops, and are increasingly influenced by diet and lifestyle, even during pregnancy and early life.

The real truth? Our genes are still shaped by the eating patterns of our ancestors. Looking back just three or four generations, it’s clear that our metabolism isn’t designed to handle constant intake of simple sugars, fast food, sugary drinks, fried foods, and processed baked goods—without the body eventually compensating, often through the development of metabolic and endocrine diseases.

Does Ozempic “eat away” at your bones?

Yes and no—it depends on how they’re used. GLP-1 agonists can lead to some loss of bone and muscle mass, but in many cases their impact is minimal. What really matters is how the weight is lost. Rapid weight loss (for example, 30 kg in 4–5 months), without proper training, can weaken bones regardless of whether it’s achieved with medication or extreme dieting and very low calorie intake. In both cases, the risk of gallstones also increases.

Weight loss with GLP-1 therapy does include some loss of lean mass. On average, about 70–80% of the weight lost is fat, while 20–30% comes from muscle mass. This applies to the general population without structured exercise. In people who train regularly—especially with resistance training—that ratio shifts, helping preserve muscle. With 2–3 strength sessions per week and regular activity, muscle loss is significantly reduced, and the negative impact on bone is largely minimized.

A recent 2025 meta-analysis in patients with type 2 diabetes found that GLP-1 agonists did not increase fracture risk and were even associated with better outcomes in BMD (bone mineral density—a measure of bone strength assessed by DEXA scans) and certain markers of bone turnover compared to controls. This doesn’t mean they “protect” bone in every situation, but it does argue against the idea that these medications inherently damage bone.

In practice: GLP-1 therapy + resistance training + adequate protein intake = preservation of muscle and bone, with weight loss coming primarily from fat.

Risks and side effects

The risk of hypoglycemia (a sudden drop in blood sugar) is very low when GLP-1 medications are used on their own (without other diabetes drugs), especially if patients eat regular, smaller meals rich in protein and complex carbohydrates. These medications are not meant to be used alongside extreme approaches like skipping meals entirely, juice cleanses, or cutting out all carbohydrates.

Instead of skipping breakfast—or grabbing a croissant or bakery sandwich—a better option is something like cottage cheese with nuts, 1–2 eggs with vegetables, or a protein shake if appetite is low. The most common side effects—nausea, diarrhea, and bloating—are often linked to continuing an unhealthy diet (refined carbs, fast food, chips, sugary drinks), and can usually be reduced by switching to meals higher in protein and fiber.

As mentioned earlier, the risk of gallstones increases with rapid weight loss, regardless of the method used. With GLP-1 therapy, it’s recommended to monitor labs (glucose, HbA1c, liver enzymes) every 3–6 months. If symptoms like sudden upper abdominal pain, nausea, vomiting, or pale/yellowish stools occur, an earlier abdominal ultrasound should be considered.

With GLP-1 therapy, the goal of breakfast is: small in volume, nutrient-dense, easy to digest, and rich in protein and fiber.

Recently, there has been discussion about a very rare but serious side effect linked to GLP-1 medications—a sudden loss of vision caused by impaired blood flow to the optic nerve (known as NAION). This is an extremely rare condition, estimated to occur in about 1 in 10,000 users. It’s important to emphasize that this is an association, not a proven cause, since many of these patients already have underlying risk factors such as diabetes, high blood pressure, and abnormal cholesterol levels.

While some analyses suggest a higher risk at higher doses, the key recommendation remains the same: therapy should be started gradually and always under medical supervision. These medications should never be obtained independently and started at the highest available dose without proper guidance.

Who should NOT take GLP-1 medications?

The main absolute contraindication for these medications is a personal or family history of medullary thyroid cancer (including cases in close relatives such as parents or grandparents), as well as individuals with MEN2 syndrome. Caution is also advised in patients with existing gallstones or severe gastrointestinal conditions.

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GLP-1 medications represent a significant advancement in the treatment of obesity and metabolic disorders, but it’s important to emphasize that they are not a “magic solution.” The benefit–risk balance favors their use in individuals with a BMI over 30, particularly when weight loss has not been achieved through diet and regular physical activity, or in those with documented metabolic conditions such as insulin resistance, prediabetes, hypothyroidism, and others. The best results are seen when these medications are combined with a balanced diet (higher in protein and fiber, lower in simple sugars), regular physical activity, and properly guided therapy.

This approach allows for a structured, comprehensive treatment of obesity that not only improves effectiveness but also reduces side effects like nausea and digestive discomfort. In summary, using these medications without proper indication (e.g., BMI ≥30), increasing doses too quickly or starting at high doses, maintaining an unhealthy diet, or skipping meals altogether are not aligned with good clinical practice and can lead to unwanted outcomes. Likewise, taking these medications without introducing regular physical activity (at least walking, swimming, or treadmill exercise 3 times per week, ideally combined with strength training) increases the risk of losing muscle—and potentially bone—mass.

GLP-1 medications do not act as a “bone-dissolving” agent. What actually happens is that rapid weight loss reduces the mechanical load on bones, which can lead to some loss of bone density if not supported by resistance training and adequate protein intake. For that reason, these medications should not be used passively, without attention to physical activity, protein intake, and, in some cases, supplementation (such as vitamin D3 and K2) during periods of more rapid weight loss.