Effects often appear in layers: early changes in appetite/routine in the first days, and more measurable weight and metabolic changes over 2–4 weeks. Some see quick scale drops in the first 1–2 weeks, partly from water/glycogen. More meaningful fat loss usually becomes clearer within a month. Studies report that certain cardiometabolic indicators can improve within weeks, but speed varies widely. Key drivers are calorie deficit, adequate protein/fiber, sleep, and stress. Compensatory overeating delays results. Track weekly waist, weight averages, and hunger control rather than single-day scale numbers. If nothing changes after ~4 weeks, adjust food quality/portions, activity, and sleep—not only the fasting window.