Weight-loss jabs like Ozempic, Mounjaro can slim you fast—but doctors warn of real risks

Weight-loss drugs based on GLP-1 receptor agonists are delivering levels of weight reduction earlier difficult to achieve. However, their rapid uptake, driven by social media, celebrity use and rising demand, has also raised concerns around misuse, side effects and long-term safety, which are still being closely studied.

Read on for what Dr Anoop Misra, Chairman of Fortis C-DOC Hospital for Diabetes and Allied Sciences and Director of the National Diabetes, Obesity and Cholesterol Foundation, says about how these drugs work, their benefits, risks and what patients need to keep in mind. These medicines are not a substitute for diet and exercise and require medical supervision.

How these drugs work

GLP-1 drugs mimic a natural hormone released after meals that signals fullness, slows stomach emptying and helps regulate blood sugar. This reduces appetite, improves satiety, and leads to sustained weight loss. These therapies have evolved from diabetes treatment to obesity management. Newer drugs such as semaglutide (sold as Ozempic and Wegovy) and tirzepatide (Mounjaro) have shown significant weight loss in clinical trials, expanding their use beyond traditional indications.

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More than weight loss

These medicines do more than reduce body weight. They improve blood sugar control and insulin sensitivity, and reduce the risk of heart attacks, stroke, and liver fat. They may also help conditions such as sleep apnoea, fatty liver disease and knee osteoarthritis, with early research pointing to possible neurological benefits and reduced alcohol consumption in some cases. Because of these effects, they are particularly useful for patients with obesity along with diabetes, heart disease, or liver conditions.

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Side effects to watch

The most common side effects are gastrointestinal, including nausea, vomiting, diarrhoea and constipation, especially during dose escalation. These affect a large number of users and can lead to discontinuation in some cases. Rapid weight loss can also lead to muscle loss, up to 30 to 35% of total weight lost in some cases, particularly in older adults, affecting strength and metabolism.

There is also a risk of micronutrient deficiencies due to reduced appetite, along with behavioural concerns such as erratic eating patterns or over-reliance on medication. Other risks, though less frequent, require monitoring. These include pancreatitis in susceptible individuals and worsening diabetic eye disease with rapid blood sugar reduction. A rare eye condition has also been reported in some cases.

Some users experience visible facial changes due to rapid fat loss, often referred to as “Ozempic face”, a cosmetic effect seen with rapid weight loss. Rare but serious complications, such as severe slowing of gut movement, can lead to persistent constipation, bloating, and abdominal discomfort. Animal studies have also suggested a possible risk of thyroid cancer, although this has not been confirmed in humans and continues to be monitored.

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Not a quick fix

Dr Misra cautions that these drugs are increasingly being used inappropriately, often without proper medical evaluation. Some individuals obtain them from unverified sources or use them for cosmetic weight loss despite not meeting clinical criteria. Many users also rely solely on medication without making lifestyle changes. Studies show that 60 to 70% of lost weight can return within a year of stopping treatment if diet and exercise are not maintained. Cost remains a major barrier. In India, these drugs can cost between ₹10,000 and ₹25,000 a month, limiting access, although prices are beginning to ease with the entry of generics.

What should patients do?

“These medications work best when combined with structured lifestyle changes, not as a replacement for them,” Dr Misra says. Doctors advise patients to eat smaller, protein-rich meals, avoid overeating or skipping meals, stay hydrated, and remain physically active, including regular strength training to preserve muscle mass. Regular follow-up is essential to monitor progress, adjust dosage, and manage side effects. Patients are also advised not to use these drugs without medical supervision, to avoid abrupt discontinuation and to report any severe symptoms promptly.

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