The short answer is – anything from a longer yet easier-effort aerobic activity, to a shorter High Intensity Interval Training (HIIT) effort, will achieve fat burning if done consistently.
There is emerging evidence that HIIT might be even more effective than other forms of exercise to achieve fat loss. This is on top of its established benefits of improved aerobic fitness, blood sugar control, blood pressure and other health measurements.
For more information, read this great article in the New York Times discussing a comprehensive study published in the British Journal of Sports Medicine.
Happy exercising people!