There is no single “fastest fat burner.” The fastest reliable results come from a calorie deficit plus higher protein intake and consistent physical activity. Stimulants like caffeine can temporarily increase energy expenditure, but long-term fat loss is driven by sustained weekly energy deficit. A practical fast-track approach is to create a daily 300–600 calorie deficit, prioritize protein, use resistance training to preserve muscle, and increase low-risk movement such as walking. Chasing “instant fat burn” with high-dose stimulants can trigger side effects like palpitations, insomnia, and anxiety. The safest speed is the one you can measure, maintain, and repeat over time.