That was this old article... http://www.timesonline.co.uk/tol/news/uk/science/article2195538.ece http://www.timesonline.co.uk/tol/news/uk/science/article2195..

That was this old article... http://www.timesonline.co.uk/tol/news/uk/science/article2195538.ece http://www.timesonline.co.uk/tol/news/uk/science/article2195... But it was discussing walking, not riding (far more efficient), and used common milk as the calorie provision (effectively a worst-case scenario).