Is Yoga a Fat-Burner?Some advocates claim that yoga burns up to 1,000 calories an hour. Is that true or false?
Q: I regularly do "hot" yoga, also known as Bikram yoga. I've read that this type of yoga can burn 800 to 1,000 calories a session. Is this true? My heart rate speeds up a lot, too. So, is this also a good cardio workout?
A: Some yoga practitioners make outlandish claims about the physiological benefits of yoga, often without any scientific proof whatsoever. The idea that yoga can burn up to 1,000 calories in a session is dubious, if not impossible, according to several studies.
Calorie burn for any activity varies according to many individual factors, especially body weight—and heavier people burn more calories per minute. Consider these typical calorie burns:
|Activity||Average calorie burn*||Typical calorie burn in 45-minute workout|
|At rest||1 to 1.5 calories per min (depending on weight)||45 to 68 calories|
|Walking at 2 mph (30 mins to walk one mile)||2 to 5+ calories per min(depending on weight)||90 to 225 calories|
|Walking at 4 mph (15 mins to walk one mile)||4.6 to 10+ calories per min (depending on weight)||207 to 450 calories|
|Running at 6.7 mph (9 mins to jog one mile)||9 to 19 calories per min(depending on weight)||405 to 855 calories|
*Calorie estimates from Exercise Physiology by McArdle, Katch and Katch
A typical yoga session lasts from 60 to 90 minutes. To burn at least 800 calories, a person would need to burn 9 to 13 calories per minute, depending on the length of the class. So the yoga session would need to be as strenuous as running 6.7 miles per hour—the entire time. Considering that much of yoga involves sitting quietly while breathing deeply, holding perfectly still postures, or doing stretches, this calorie-burn claim doesn't even come close to making sense.
A 2007 study in the journal BMC Complementary and Alternative Medicine measured 20 regular yoga practitioners while they performed a 56-minute beginner-level hatha yoga routine while inside a respiratory chamber. On average, the participants burned 3.2 calories per minute. Another 2005 study in the Journal of Strength and Conditioning Research measured 26 women while they performed 30 minutes of hatha yoga. The women burned an average of 2.3 calories per minute. So it appears that the average yoga workout may burn about as many calories as a very light person walking very slowly.
|Activity||Average calorie burn||Typical calorie burn in 45-min workout||Typical calorie burn in 90-min workout|
|Hatha yoga||2.3 to 3.2 calories per min||104 to 144 calories||208 to 288 calories|
Of course, some types of yoga, like ashtanga or Bikram, are more active than hatha yoga. When people move through asanas, or yoga poses— quickly, they can feel hot and sweaty and experience muscle fatigue. So, could more vigorous forms of yoga produce a tremendous calorie burn that slower types of yoga do not?
Not according to the research. A 2007 study in the Journal of Bodywork and Movement Therapies tried to compare different styles of yoga, recognizing that some types are more vigorous than others. So, they measured 16 people while they performed ashtanga (known to be a highly vigorous form of yoga), as well as hatha and gentle yoga workouts that lasted 80 minutes each. All the sessions included the more active postures found in each style of yoga as well as some relaxation or passive poses.
The researchers found that participants started out with resting hearts rates of between 67 to 70 beats per minute. They achieved an average heart rate of around 74 to 80 beats per minute during the hatha and gentle yoga sessions, and around 95 beats per minute during the ashtanga. When they looked at heart rates during only the most vigorous portions of each routine (the postures rather than the deep breathing meditations), they were about 3 to 5 beats per minute higher, on average.
The hatha and gentle yoga routines raised participants' heart rates to around 42 to 45 percent of their maximum heart rate, which is below the threshold for moderate-intensity cardio activity. The ashtanga session reached a 54 percent threshold, leading the researchers to conclude that this workout may contribute to increases in cardio-respiratory fitness in people who are unfit or not physically active.
One problem with the study is that the number of people tested was small, and half of the subjects had performed yoga at least once in the week prior to the study (suggesting that they were trained and fit to do yoga). Six of the participants had never done yoga. Because they were untrained, they would likely exhibit a different physiological response to the workouts. But the researchers failed to distinguish between the groups.
Even if they had, the numbers were so small that it would be statistically difficult to come to any reliable conclusions. It may be that only those who were new to ashtanga were getting the higher heart rates, and even then they were barely enough to constitute the moderate-to-vigorous intensity cardio workout that walking, cycling or running provide. Those who were used to yoga were probably working at an even lower intensity, and therefore probably not meeting general cardiovascular recommendations from the workout.
Is Bikram better?
While these weren't Bikram workouts, it's unlikely that hot yoga burns more calories just because it may raise your heart rate higher. In reality, the huffing and puffing and heavy sweating found in many yoga rooms is due to the hot room, not the hot yoga. The Bikram method recommends turning up the temperature to a minimum of 105 degrees and aiming for 40 percent humidity in the room.
Ever try standing outside in Houston in August? Ever try running in Florida in the summer? Not only do you sweat more when it's hot and humid, when you sweat, you dehydrate yourself. And the more dehydrated you are, the higher your heart rate goes. When you sit in a sauna your heart rate rises high, too, but it's not because you're burning more fat or calories. It's because your heart is working extra hard trying to cool you off. In fact, for some people, exercising in this type of environment isn't safe. And it certainly isn't a great way to lose weight.
While any movement is a good thing, especially for those not in good physical condition, these study results are not a resounding stamp of approval for using yoga to improve cardio fitness or to burn extra calories.
But some people are convinced that yoga is a good way to achieve weight loss. If so, it may be more from the mental self-discipline that the yoga philosophy instills, rather than the workout. Neither the calorie burn nor the intensity of yoga appears to be enough to make much of an impact on weight at all.
Yoga slows down metabolism
In fact, one recent study showed that long-term yoga practice seems to slow down metabolism. A 2006 study in BMC Complementary and Alternative Medicine compared 104 men and women; 55 were regular yoga practitioners for at least six months or more, and the other 49 did not practice yoga at all. Basal metabolic rate was measured using an indirect calorimeter to monitor oxygen consumption. The yoga group had a 15 percent lower metabolism, even after adjusting for heavier and lighter body weights.
Regular yoga can decrease sympathetic nervous system activity, or a person's level of arousal (which is why it helps de-stress you). So finding that these practitioners had a slower metabolism makes sense. The researchers speculated whether this lower metabolism may make it more likely for a person who does yoga to gain weight or body fat, and they noted that higher body-fat levels can be seen at lower BMIs.
Does this mean that you should avoid yoga? Not necessarily. Just recognize why you're doing it. If you're trying to lose weight, more cardio and healthier eating is the answer (read my other columns for more information). But yoga is a good workout if you need to wind down, focus or improve your flexibility and balance.
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