As the use of anti-obesity medicines like Ozempic continues to grow, more people are trying to understand what daily life looks like on these injections. Beyond weight loss results, concerns often centre on side effects, especially those linked to digestion. Many users of GLP-1 agonist medicines report gastrointestinal issues such as nausea, vomiting, constipation, and heartburn. In recent months, another pattern has caught attention. Several people say they feel sick after eating greasy or oily food.To understand why this happens, we spoke to Dr Pratayksha Bhardwaj, World Record Holder Dietician and Weight Management Specialist, who explains that this reaction is more common than people realise.What Ozempic Does Inside the BodyOzempic, medically known as semaglutide, was originally developed to help manage Type 2 diabetes. It is now widely prescribed for weight management because of how it influences appetite and digestion.According to Dr Bhardwaj, Ozempic works by slowing down gastric emptying and acting on appetite-regulating centres in the brain. “Food stays in the stomach longer, and the feeling of fullness comes earlier than usual,” he explains. This change helps people eat less but also alters how the body handles certain foods.Why Greasy Food Can Trigger Nausea On OzempicFatty and oily foods naturally take longer to digest. When this process is further slowed by Ozempic, the stomach can struggle to cope with heavy meals.Dr Bhardwaj says that eating large portions, especially foods high in fat, can overwhelm the digestive system. “When fatty foods sit in the stomach for too long, they can trigger nausea, vomiting, or even diarrhoea,” he notes. This is why some people feel unwell shortly after eating fried snacks, fast food, or rich gravied dishes.Is This an Allergy or Something Else?Many patients worry that vomiting after eating greasy food might be a sign of an allergic reaction. Dr Bhardwaj clarifies that this is not the case. “This response is physiological, not allergic,” he says. It reflects how the body adapts to the medication rather than an intolerance to the drug itself.Clinically, doctors observe that tolerance for oily foods drops sharply after starting Ozempic. Vomiting is more commonly reported during the early stages of treatment or when the dose is being gradually increased.Can This Side Effect Be Beneficial?Interestingly, this reaction can support healthier eating habits. Dr Bhardwaj points out that the discomfort acts as a natural reminder to change food choices. Patients are often advised to eat smaller portions, reduce fat intake, and include more fibre-rich vegetables in their meals.Lower-fat foods are easier to digest and less likely to cause nausea. Over time, many people find that their preferences shift away from heavy, greasy meals.When to Seek Medical Advice?While occasional nausea can be expected, persistent vomiting should not be ignored. Dr Bhardwaj advises consulting a doctor if symptoms continue. In some cases, a dose adjustment or personalised nutrition plan may be needed to reduce discomfort while continuing treatment safely.Ozempic can be effective, but understanding how it interacts with food is key to managing side effects and maintaining long-term health.