Cardio or Weights?

 What Burns More Calories: Cardio or Weights?

Someone requested a few weeks back that I write on this topic and I've been working on it for awhile now and I think I finally have a rough attempt at an answer. I'm actually going to split it up into two sections. So here it is, the answer to the question: what burns more calories, cardio or weights? Part 1:

I am going to be annoying and give the cliche answer of "it depends." I know I know, not the answer you were looking for.  But it's true, the amount of calories expended during a bout of exercise depends on a lot of different factors.  The most influential factor probably being the INTENSITY of exercise being performed.  For example, if your "cardio" consists of walking for 30 min at 2 mph you are not going to burn that many calories.  However, if you are doing repeat 400m sprints for an hour you are going to expend a lot more calories at that intensity.  The same goes for resistance training.  You won't expend that many calories if you are going through the motions or sitting on the biceps curl machine doing 100 curls while people watching.  On the other hand,  if you are performing a high-intensity, total body circuit-style workout you will burn more calories.  Another factor that influences calorie expenditure is the duration of exercise.  You will obviously burn more calories if you go out jogging for 3 hours versus 30min.   And the last factor that seems to play a major role in the amount of calories you burn during exercise is body mass, or more specifically lean body mass (the amount of muscle you have).  There is a direct correlation between lean muscle mass and caloric expenditure; meaning the more muscle you have the more calories you burn.

With all that being said, if you are trying to directly compare which type of exercise burns more calories and you try to equate exercise intensity and duration (i.e. comparing 1 hour of cardio at 70% VO2 Max with 1 hour of lifting weights using 70% of your 1 Rep Max), a cardio workout can burn almost twice as many calories as a bout of weight training.  For a 200 lb male working at this intensity and duration, he would probably burn ~500 calories doing a cardio workout and ~250 calories lifting weights.  Be forewarned that this is a very rough estimate and a lot of other factors can influence this calorie expenditure other than the ones previously mentioned, such as exercise selection, age, diet, and sleep.
   
Now, even though you may burn almost twice as many calories performing cardio exercises compared to lifting weights that doesn't mean you won't benefit from resistance training. In fact, in the long run you may be better off lifting weights if your overall goal is to burn calories and lose weight.  As I mentioned before, the more muscle you have the more calories you burn and the best way to increases muscle mass is through resistance training.  There is also a phenomenon referred to as Exercise Post Oxygen Consumption (EPOC) that suggests you burn more calories throughout the day following a bout of weight lifting than you would after a cardio session but I will get into this more in Part II.