Thanks to decades of research that dove into the best exercise for weight loss, we now know that both strength training AND cardio are crucial pieces of the weight loss (or maintenance) pie. Gone are the days when fitness buffs would pedal away for hours on end on the elliptical. Strength training not only keeps us strong and able to tackle tasks like lifting heavy bags of groceries to climbing several flights of stairs, but it also stokes us up with muscle cells that burn far more calories than fat cells. (Up to three times more, according to many estimates!)