Burning Fat: Cardio or Fat Burning?

March 18, 2005 8:08 AM

So I go to the gym semi-regularly and use the Elliptical machine. It has some built-in routines. One is called "fat-burning" and one is called "Cardio Workout". The fat burning sets a target heart rate in the 120's (number made up) while the Cardio sets my target heart rate somewhat higher -- maybe the low 140's. My question is, which will actually burn more fat, the Fat Burn or the Cardio?
posted by petestein1 to health & fitness (21 comments total)

The idea is that you need to work your heart either way, but that at higher heart rates (and harder work your body's doing), it may stop doing aerobic metabolism (using fat/lipid), and convert to anaerobic, because your body can't keep up with the amount of energy you're requiring it to use. I'm not sure which will "burn more fat," but I think for weight loss, you need to focus on number of calories burned and number of calories you intake each day.
posted by gramcracker at 8:22 AM on March 18, 2005

I am not a doctor/physiologist/trainer, but my understanding is you cannot "burn fat". When working out, use use glycogen as fuel which comes from the carbohydrates you've eaten. If there are no carbs available, the body will go to its fat stores. However, if you run out of available carbs during your workout, you will "bonK, or "hit the wall". (Never happened to me, but I understand it is extremely unpleasant. And symptoms vary.)

This is my very simplified understand of it. Maybe the bigger brains should chime in as well.
posted by ObscureReferenceMan at 8:26 AM on March 18, 2005

the higher the heart rate the more energy you use the more fat you burn, per unit of time.
however, in general you can burn more fat if you go for longer, which most people can do if they don't exhaust themselves too quickly. so if you go for 40 minutes in the 120s this burns more fat than 15 minutes at 140.
posted by alkupe at 8:26 AM on March 18, 2005

Indeed I'm focusing on weight loss.

In reality, I'm talking a few pounds here. I was the same weight for a decade+ and then I hit 30 and bam! I put on a little 3 pound gut. I figure its better to stay on top of it than try to lose 25 pounds a decade from now.

So from what you say I'm better off working less and keeping my heart-rate lower. That's seems to counter-intuitive -- the calorie counter on the machine says I burn more raw calories at the harder Cardio level than the easier Fat Burning level. Also, doesn't hitting that Cardio level help keep my heart rate up all week long and therefore burn fat 24/7?
posted by petestein1 at 8:27 AM on March 18, 2005

If you're after the best "fat/calorie burn", try using the Interval Training option. Interval training (periods of hard, high resistance combined with short bursts of very fast, easy going) is very efficient at both exercising your heart and burning fat/calories, both while you do it, and afterwards. On a Precor it's #8. It will kick your ass. It's the most efficient fat burning, calorie burning workout on the machine, in my opinion. I go to the gym at 6:45 every morning and ride the beast, and I was getting no action at all on the Fat Burn or the Cardio, but when I switched to Interval Training about a month ago (after happening to catch something about it on tv while working out) I can already see the difference in how my clothes fit, and I just look better. I don't weigh myself, but I do have eyes, and IT absolutely works for me, where nothing else did. I do it 7 days a week. If I do 35 minutes of IT on an intermediate level, I burn approx. 400 calories.
posted by iconomy at 8:31 AM on March 18, 2005

if this is in response to me you reversed that
what i meant was the opposite. if you get a higher heart rate but tire really quick and stop this burns less than a longer less intesive workout.
definitely if you're talking about working out for the same amt of time, then the higher the heart rate the better.
i don't think cardio sessions burn fat 24/7. you should build muscle (lift weights) for that. the bigger muscles use more energy 24/7
posted by alkupe at 8:35 AM on March 18, 2005

Alkupe, I was in fact responding to you -- sorry, didn't mean to reverse things.

Currently I do the Cardio routine for 30 minutes at level 9 or so and burn (according to the machine) about 425 calories. Honestly? I could go longer on Cardio, I just get too bored/need to free up the machines for others.

Iconony, interesting to hear you say that you burn about 400 in 35 minutes -- that's the same as me on Cardio only. But I'll try what you say.
posted by petestein1 at 8:40 AM on March 18, 2005

alkupe is right: if you add in some weight training, you'll add some muscle bulk. And having more muscle means larger muscle cells, so each requires more energy; you'll use your energy stores faster. Just remember that muscle weighs more than fat, so don't be surprised if you don't lose pounds on the scale.

1 pound equals 3500 calories. You can pick your way of losing it: eat 500 less calories a day, and you'll lose a pound a week. Eat 200 less, burn 300 more, same thing.

If you have the time to do the fat-burning for longer, you'll probably burn more calories, because you're able to do the machine longer; you'd tire faster on the cardio setting. Also, no, the cardio setting won't keep your heart rate higher the entire week. After you've exercised, your heart rate will drop back down to its normal resting rate.
posted by gramcracker at 8:41 AM on March 18, 2005

Gramcracker, thanks for reminding me that more muscle = weighing more. I'm not really all that much into how much I weight, it's more the little gut and the body fat measure on my scale.

Yes I know this measure is not very accurate but I weigh myself every morning at the same time and in the same part of my daily routine and note the weight and body fat. What matters to me is the measure relative to other days, not the actual number.

The body fat measure moves around slowly between 15% and 17%. When it hits 17% it worries me and I try to spend a few weeks getting back down around 16%. If I can stay motivated and knock it down to 15%... great!

Throughout all of this my weight moves around between 156 and 159. (I'm 5' 10" BTW so you can see that my BMI is just fine.)

I'll have to try the fat burning and try to go for a full hour and see how many total calories I can burn. I can probably knock off an extra 200 or so. Then again, I could just skip dessert for a night (relatively easy for me) and knock them off with a lot less sweat and time.
posted by petestein1 at 8:52 AM on March 18, 2005

Currently I do the Cardio routine for 30 minutes at level 9 or so and burn (according to the machine) about 425 calories.

FYI, I'm told that those counters (I assume you're using the machine where the HRM is in the handgrips) can be off by as much as 30%.
posted by scratch at 9:01 AM on March 18, 2005

petestein1, when I raise the resistance and the ramp level, I burn more, and when I pedal faster, I burn more as well. 400 is the low end, 700 when I really push it, although I can be lazy and not feel like pushing it. Plus, being a man (I think?) you probably have more muscle mass than I do and I have no doubt that you're burning more calories than I am. I'm working on getting up to an hour, too - it's very addicting!
posted by iconomy at 9:03 AM on March 18, 2005

OK, so now I can show my ignorance and ask the question that I've been too embarrassed to ask anyone:

How exactly do you set your tempo on those machines? For example, iconomy talks about the interval training option on the Precor machines. The ones at our gym have the option, but really no guidance on what is the correct tempo for the high resistance and the low resistance cycles there? How many steps/min do you target for both of those? Or do you use some other criteria? (the heart rate monitor doesn't work for me; for some reason all I get from those things is an error message, perhaps I'm already dead and don't know about it!)
posted by tuxster at 9:10 AM on March 18, 2005

Tuxster, I had a girlfriend who could never get the heart rate monitor to work either. If I recall, there were two things that helped.

First, she removed her metal watch.

Second, instead of making a tight grip, she'd hold it with her fingertips... thumb on one side, other fingers 180 degrees opposite.

That worked for her.
posted by petestein1 at 9:16 AM on March 18, 2005

petestein1, I've gone through all those cycles. I no longer wear a watch, and tried holding it all kinds of ways. Sometimes it works (when I use a hold similar to what you mention), but even then it just jumps around. It'll show 70 one second, go upto 120 the next 2 seconds and come back to 85. Either I have a very irregular heart that sometimes doesn't beat and other times goes bezerk, or I just have to give up on those heart monitors...

That's why I would like to see if I can use some other criteria to set my tempo, so that I know I'm doing it right (it's too easy to be lazy and go with the same tempo while watching Seinfeld reruns).
posted by tuxster at 9:25 AM on March 18, 2005

Tuxster, alternatively you could spring for a heart monitor that uses a strap across your chest. I have no idea what they cost but I assume they're more accurate.
posted by petestein1 at 9:36 AM on March 18, 2005

A few points to set the record straight:

1. Your body has two different 'fuel sources': glycogen (carbs) and lipids (fat). Each is turned into energy via a different pathway: glycolysis and lipolysis, respectively. At any given time, your body is using some balance of both.

2. Lipolysis is less efficient, so in shorter, more intense periods of exercise, you use glycolysis more. Hence the 'fat-burning' mode, which attempts to keep you at a low enough level of exertion to favor lipolysis. As the name implies, at least during the exercise period, 'fat-burning' mode will likely burn more fat.

3. The problem with 'fat-burning' mode, and the (usually not terribly accurate) calorie counters on workout machines, however, is that exercise actually helps you lose weight in two ways: it burns calories while you're doing it, and it elevates your metabolic rate for a period after you stop.

4. Intense exercise for a short period of time, while burning fewer calories (and less fat) during the exercise, leads to a much greater post-exercise metabolic rate increase. So much greater, in fact, that it leads to considerably larger total number of calories (and stored fat grams) burned over the course of the day.

5. In other words, in the total (i.e. during + after) picture, 60 minutes in 'fat-burning' mode is actually less effective than 20 minutes of intense interval-based training.

6. Similarly, as several other people have pointed out, muscle is metabolically active - it burns calories even when you're sitting on the couch. So adding weight training to your cardio is probably a wise idea. Be advised that muscle is much denser than fat, so that replacing five pounds of fat with five pounds of muscle would leave you weighing in at the same point, though looking much slimmer. Go by the old 'naked in front of the mirror' test, by how your clothes fit, and by how you feel in general. They're all far more effective than your scale.
posted by thomascrown at 9:38 AM on March 18, 2005 [3 favorites has favorites]

Thomascrown, thank you for the thorough write-up. One follow-up question... you say:

< 60 minutes in 'fat-burning' mode is actually less effective than 20 minutes of intense interval-based training.>>

Why interval-based as opposed to straight cardio? Isn't interval an alternating pattern of fat-burning and cardio?

Or is the cardio in interval training at a harder level than the straight cardio?
posted by petestein1 at 9:46 AM on March 18, 2005

Also, to everyone, while I welcome more facts, opinions and ideas, I just wanted to say thank you for making my first Ask MeFi experience such a great one!

This is an incredible resource.
posted by petestein1 at 9:46 AM on March 18, 2005

tuxster, on the machines at my gym, when you select a course, the ramp, the time, and the resistance are preset. You can try the course on the preselected settings, and then decide if you'd like to increase the resistance, or raise the ramp. I choose #8, Interval Training, like I said. The program starts automatically with the resistance set at 1. I raise it to 4, where it stays the entire time. The ramp raises and lowers automatically depending on what part of the program I'm on, but I can always increase or decrease that myself as well. As far as the time goes, that's the beauty of the program - it's all figured out for you. On the Precor any program is separated into 15 segments. If you opt for a 30 minute workout, each segment is exactly 2 minutes long. If you go to a 35 minute work out, each segment is 2 minutes and ...um...some amount of seconds. If you go to an hour, each segment is 4 minutes long. You don't have to think about it or wonder when to change your intensity or your ramp height - the machine does it automatically for you.
posted by iconomy at 10:43 AM on March 18, 2005

Intervals are the way to get fit faster. If you've got a limited amount of time just blow off the 'cardio' and 'fat-burning' setting and choose the interval setting like iconomy said. Also, the calorie counts are hopelessly optimistic. This might sound a little gross, but if you are having a hard time getting a reading from holding the electrodes a little spit or sweat will increase the conductivity. Just wipe the machine down afterwards. If you really want to do heart rate training, a cheap chest strap HRM is essential.
posted by fixedgear at 2:44 PM on March 18, 2005

PeteStein1:

The rationale for intervals rather than 'steady state' is that you can push the intervalled peaks far higher than you could maintain for a 20' steady state session.

For what it's worth, the two 'easiest' ways to do intervals effectively would be to either set a fixed-duration rotation (one minute of hard running, followed by one minute of easy running, ten times) or to do a handful of escalating cycles (easy jog one minute, slightly harder next minute, decent run third minute, bust your booty the fourth minute, repeat five times.)

If I'm standing on my fitness soapbox here, I would be remiss if I didn't throw out a few other things. As I compete regularly in full-contact mixed martial arts (and there's nothing like the threat of getting your a$! kicked in front of a crowd regularly to keep you motivated at the gym), I've leveraged my neuroscience background and dorked out by following exercise research a bit more closely than is probably in the interest of sanity. Three conclusions:

For people looking to push their cardio to the max, research seems to indicate that the Tabata Protocol yields the best increases in both aerobic and anaerobic abilities. It's very brief, but absolutely brutal, so skip it unless you're willing to take some pain for your gains.

Rather less scary are kettlebells, which are what I recommend to friends looking for easy ways to stay in shape. While kettlebells run about $80 a pop, you can get all the cardio and strength training you need from just one, and subsequently drop the gym membership altogether. They take up almost no space, are extremely time-effective, and yield far faster, more functional results than the standard weight machines / treadmill tack.

Finally, for anyone looking to push themselves to the highest possible fitness gains, I'm a big proponent (and ongoing follower) of CrossFit's free Workout of the Day. Despite being brief, their workouts are exceedingly tough; but, for me at least, it's more than worth the effort.
posted by thomascrown at 4:43 PM on March 18, 2005