I had lost 45 lbs (350 to 305) and then had lost track of my weight loss over a few months span. I purchased a bike 2 months ago and I've lost 20 lbs. I ride it 6 days a week for at least 50 minutes. I do HIIT two of those days and I ride to work once or twice a week, which is 30 miles round trip. My polar watch shows a calorie loss of around 860 each way. Not too shabby! But yes, a bike is a great form of cardio, I prefer it over any other cardio. Beats jogging or sitting in a gym, unless I'm doing weights.