If not losing weight on Mounjaro, common reasons include inadequate dosage or not enough time on the medication, eating more calories than realized, lack of physical activity, or underlying health/ metabolic issues. Mounjaro works by suppressing appetite and improving insulin sensitivity, but it takes several weeks to show significant fat loss, especially at higher doses like 10mg or 15mg. Weight loss can stall if diet still involves calorie surplus or processed foods, and if exercise isn't combined. Also, initial rapid loss might be fluid, with fat loss taking longer. Monitoring portions, improving diet quality, increasing physical activity, and ensuring proper dosing are key to success on Mounjaro.