What it means
The name comes from heart-rate zone systems that split effort into five bands. Zone 2 is the second-easiest, often placed at roughly 60 to 70% of maximum heart rate, though definitions vary between coaches, devices and labs.
A simpler guide is the CDC talk test. At moderate intensity you can talk but not sing. Zone 2 sits at the easier end of that range: breathing is deeper, but conversation is comfortable. Brisk walking, easy cycling, swimming and elliptical work are common choices.
Zone 2 is popular for building an aerobic base with low injury risk and less fatigue than hard intervals. Minutes spent there count toward the 150 minutes of moderate activity a week in the US guidelines.
Claims that zone 2 burns fat in a special way are often overstated. For weight loss, total activity and the overall calorie deficit matter more than the exact zone.
Why it matters
Zone 2 work is a gentle way to build fitness when GLP-1 side effects make hard workouts feel rough.