The treadmill at the gym shows two heartbeat “bands”. One says “Cardio Training Zone” and one says “Fat Burning Zone”.
The Cardio might be like 150-180 beats per minute, and the Fat burning is like 120-150.
My question is this: If my goal is to “burn fat”, should I be running in the “fat burning” zone or does the “cardio” zone give me the benefits of BOTH Cardio and Fat burning. I ask because I regularly work out in the “cardio” zone but don’t feel like I’m burning as much fat as I could.
It seems obvious that “cardio” should do the fat burning better, but I know sometimes physiology can be counter-intuitive.
Follow-up – this is probably one for the ages, but what’s better “fat-wise”, 20 minutes in the cardio zone or 30 minutes in the fat zone?
Thanks.
background: since knee surgery a couple years ago, I’ve put on some weight. My goal of exercising has never been to “lose weight” but rather just to “be in shape”. BUT, having less weight will be better for my knee in the long run, and is better for my cycling. Regular road running irritates the knee a bit – the treadmill is more comfortable for it.
I’m no expert, but I’m sure one will be along soon to refute what I’m about to say.
Here’s what I’ve found through reading and personal experimentation:
The “fat burning zone” tends to be at a lower heartrate. IIRC, the idea is to stay exercising for a longer time period, thus burning more fat. Most people’s bodies burn the energy currently in their bloodstream for the first 15-20 minutes of exercising, then they move on to the fat reserves. Therefore, if your goal is to burn fat you should exercise at a pace that allows you to stay active for longer than 15 or 20 minutes. Thus the “fat burning zone.”
According to what I posted above, 30 min in the fat zone is better than 20 min in the cardio zone.
Other factoids of interest:
everyone’s heart rate is different. Those damn charts mean very little. The machines are notoriously bad at detecting heart rate. Unless you’re wearing a heart rate monitor (one of the ones with the strap that goes around your chest) I’d just ignore what the machines say.
ANY exercise is better than none. Sure, it’s good to say that you should do 60 min of exercise a day. But many of us don’t have the time for that. If all you can do is 30 min, do it and be happy.
From what I’ve found from wearing a heart rate monitor, getting off your ass and doing something is 90% of the battle. The calories burned from running as fast as you can for 30 min versus running at an easy pace for 30 min are negligable (~50 calories for me); the calories burned from running for 30 min at an easy pace versus sitting your ass at a desk is huge.
I really don’t have a problem getting off my ass. I’m actually in pretty decent shape heart/lungs/muscle wise. I’m just carrying around a gut that I’m trying to burn off and I was wondering if there was some reason that going too hard make burning fat less efficient.
I thought that there were benefits of being in the “aerobic” zone versus the “anaeroic” zone (and vice-versa) that might have something to do with this.
But, I do find myself going “hard” for 20 minutes a lot more than going “medium” for 40 and that’s probably why I’m not burning it as fast as I expect.
ultrafilter – is that so?
for one, I always thought that better aerobic shape led to decreased at-rest metabolism.
My wife says if I lifted more, and increased muscle mass, my at-rest burn would be more.
I don’t necessarily equate more muslce mass with better aerobic shape, though.
Anyway, the upshot of all of this is just to be diligent about exercising, which I mostly am.
(oh, and then there’s my meat/bread/beer diet – but I’m trying to look at the exercise independently of that).
Your body has three “tanks” from which to get energy: available carbohydrates, fat stores, and glycogen. Available carbohydrates are the carbohydrates that are floating around your system and have not yet been converted to fat. Fat stores are the fat in your body which can be converted to carbohydrates. And glycogen is like rocket fuel. It’s a substance which can easily be converted into glucose for energy.
Depending on how hard you’re working, your body gets the energy it needs from the different tanks. At low levels of exertion, most of the energy is coming from the available carbohydrates. At moderate levels of exertion (fat burning zone), most of the energy is coming from the fat stores. And at a high level of exertion (cardio zone), most of the energy is coming from glycogen.
In terms of losing weight, it doesn’t matter so much in which zone you exercise as long as you’re burning calories. So, for example, if you did a light workout of walking and burned 500 calories, you may have used up the available carbohydrates in your system. Then later when your body needs energy for its normal tasks, it’ll convert fat into energy. So you’ll still lose fat even if you’re not working out in the fat burning zone, but it’ll just happen later. If you do a strenuous workout and burn your glycogen, your body will later convert fat into glycogen to replace what was used.
An advantage of doing a strenuous workout in the cardio zone is that you will experience a post exercise caloric expenditure that may be 50% of the calories you used during the exercise. So run hard and burn 500 calories, then lose another 250 calories during the day as your body recovers from the strenuous workout. The PECE only seems to happen with strenuous workouts.
So in terms of losing fat, it doesn’t matter so much if you stay in the fat burning zone. Overall, you’re better off in the cardio zone since you’re burning calories quicker (more calories per minute) and you’re getting more of an aerobic workout. However, you need to look at the calories used in the different workouts. If you’re getting exhausted in the cardio zone and cut your exercise short, you might be better off doing an easier exercise for a longer period of time so that you burn more calories overall.
filmore and ultrafilter are dead-on. I suggest you read Covert Bailey’s Smart Exercise: Burning Fat, Getting Fit. It is easily the best book for explaining the sometimes contradictory recommendations you hear, even if the title is a bit cheesy.
Originally Posted by Trunk
for one, I always thought that better aerobic shape led to decreased at-rest metabolism.
Actually, that’s true: your metabolism becomes more efficient as you get into better aerobic (or any kind) of shape. So when you’re in shape, your resting pulse and respiration rate tend to be lower than when you’re out of shape. ( For example, Lance Armstrong’s resting pulse is somewhere in the 40’s, as I recall.)
In addition, your maximum pulse rate, which occurs when you put in maximum effort, will be higher when you’re in good shape than when you’re in bad shape.
Note that this higher rate occurs with higher effort. If your aerobic self and your fat self are engaged in the exact same activity, say walking a mile in 25 minutes, then your aerobic self will require less exertion than your fat-self and you will burn fewer calories than you would have when you were fat.
But when your two selves are asked to ‘run as fast as you can,’ the aerobic self will achieve a higher pulse/respiration than the fat self.
But I’m not sure that any of this is getting at your original question. Maybe you could think of it this way: if you only exercise below the aerobic window, then you will get thinner, but you won’t be improving your cardiovascular fitness as much. So you might look good but still keel over with a heart attack. So I’d suggest trying to stay inside that aerobic window, but stay at the low end of it so that you can continue exercising for a longer period without having to stop from exhaustion.
Make sense?
And I forgot to explain, that ‘aerobic window’ is when your heart rate is in the 60-80% range of your maximum heart rate.
The standard rule of thumb for calculating your max is to subtract your age from 220. So if you’re 40, your max pulse is about 180 beats per minute, so you need to exercise so that your heart rate stays between 108-144 bpm. To exercise longer (and burn more fat), stay closer to that lower number.
I really do need to improve my diet, which I tend to be stubborn about. I did a marathon one year ('97) and could eat/drink whatever I wanted while training and still lose weight.
So I still have this notion that I can overcome any diet with enough exercise. But, I don’t exercise even nearly at those same levels as I used to.