If a runner expends 1850 kJ/hr, how long (hr) does she have to run to work off 9 lb of body fat? 1 cal = 4.184 J. Determine to one decimal place and do not include the units with your answer. The nutritional calorie (Calorie) is equivalent to 1 kcal. One pound of body fat is equivalent to about 4.1 x 103Calories.