Answer: at least 150 minutes and the exercises could be walking, swimming, biking, and an elliptical. Personally if I was 200lbs I would pick walking or swimming because when swimming your weight is being supported by the water and it burns much more calories than biking because it conducts heat twice as fast forcing your body to burn calories faster meaning you could reach a healthy weight sooner if you stick to eating healthy or a diet than by biking or using an elliptical