~Altitude Research Center, University of Colorado School of Medicine
Video of interview is at this link. Full transcript below:
Can you tell us about your area of expertise?
My background is in emergency medicine and high-altitude medicine. I’ve been doing both for about 40 years. I did special training in high-altitude medicine at the University of Colorado and I’ve always been attracted to the mountains, living in the mountains, playing in the mountains, and always interested in the effect of high altitude on human physiology and health.
How did you become an expert in high-altitude medicine?
I started as a climber and as a trekker and became interested in high-altitude medicine right out of training. My first job was as a helicopter rescue doctor in Yosemite and from there I went to Nepal and helped to start the Himalayan Rescue Association where I lived for six years at 14,000 feet doing research, taking care of sick trekkers, climbers, and locals, and that took me into my own research lab on Mount McKinley or Denali in Alaska at 14,000 feet and research projects in Tibet, South America, China, Alaska. I’ve been all over the world, all the mountain ranges, to all the places where high altitude peoples live, and where low-landers go to recreate at high altitudes or work at high-altitude mines and telescopes. I’ve been very actively involved and got in on the ground level so to speak about 40 years ago when the field was just starting.
How does altitude affect metabolism and appetite?
High altitude has a significant effect on both metabolic rate and appetite which is why people who live at altitude tend to be thinner and which is why high altitude can actually be used to lose weight. At very high altitudes, it’s a big problem in climbers because there’s too much weight loss and too much muscle mass loss. So basal metabolic rate is increased because of the hypoxia or lack of oxygen and at the same time, appetite is suppressed and there’s a switch in metabolism between the fatty acid metabolism and carbohydrate metabolism. The net result is that the high-altitude environment or simulated high-altitude environment produces changes in body fat, muscle structure, lean muscle mass, total body weight, and total body water.
How much weight do people lose on average when sleeping at altitude?
So how much weight could you expect to lose with one of these hypoxic devices? It depends on a number of factors. It depends on the degree of hypoxia or how high the simulated altitude is, your genetics, your gender, your physical condition, and other medical conditions. One study done in Holland with 20 obese people lost an average of 1 lb/week for the duration of this study and that might be a reasonable goal to shoot for but there has to be a fair amount of flexibility in your expectations because it really depends on a number of factors. A pound a week would be a good ballpark figure to shoot for.
How does altitude affect hemoglobin levels and red-blood-cell mass?
Just like real altitude, simulated altitude increases the hemoglobin mass by increasing the number of red cells in the body. With these simulated altitude devices, you don’t have to worry about getting too high or your blood getting too thick. It can’t really increase it that much. You’re only going to be at 8,000 feet to 12,000 feet and only for 7-8 hours a day and all the studies and athletes show that yes it can increase your red cell mass a little bit, but not enough to cause any health problems. As a by-product or as a side effect that could even increase your exercise performance if you’re a moderate to elite athlete.
How does the body adapt to hypoxia on a cellular level?
Every cell in the body reacts to low oxygen levels. There’s a master switch called HIF which is present in all the cells in the body that senses the amount of oxygen in the cell and in response to a low oxygen level, will latch on to the DNA and cause an expression of genes, either up-regulation of genes, or down-regulation of genes and we now know that it impacts thousands of genes, not just a few genes. So evolutionarily, we’ve developed an amazing adaptive response to low oxygen levels. After all, we have to have oxygen in order to live, and so the body has all these incredible redundant mechanisms and multiple mechanisms to try to protect the body from lack of oxygen and it’s on a cellular level.
How high and for how long do I need to be at altitude to trigger these responses?
The greater the altitude stress, the higher the altitude. In other words, the more likely these changes take place. This isn’t very well studied, this particular aspect, but around 7,000 or 8,000 thousand feet is where this change in metabolism and appetite takes place, and the higher you go, the greater those changes but you need to be at least 7,000-8,000 feet for most people. Duration at altitude is also an issue. The longer you live at high altitude, the more your metabolism is going to be changed. Your weight may be stabilized at a lower weight over a period of time. There’s some evidence that if you go to altitudes say 8,000 feet for just a week or so, your body will start to acclimatize to the point that your appetite won’t be suppressed anymore and your metabolism won’t change so much but that’s not entirely clear. There’re also some differences in gender. Men seem to be more impacted by these changes than women. There doesn’t seem to be any definite influence on age. We’re assuming we’re talking about healthy people that are going to lose weight. There’s evidence that if you’re overweight to begin with, you’re going to lose more weight. There’s also evidence that if you have metabolic syndrome, which is overweight glucose intolerance, or near-diabetes and hypertension that altitude exposure can be beneficial for the entire syndrome. So, the altitude is important and the duration at altitude is important for all these changes.
How is this possible if I’m only exposed to altitude for 7 hours per day? What about the other 17 hours?
It might be surprising to think that this technique actually works when you’re only in the simulated altitude exposure for 7-8 hours at night. What about the other 16, 17 hours a day? Well, that’s why the simulated devices aren’t quite as good as actually living at high altitude. But it’s impressive that even seven or eight hours a day of exposure will produce these benefits of increased metabolic rate and a decreased appetite. It seems to last throughout the day so the hypoxic exposure has effects that go beyond the number of hours you actually spend at simulated altitude. It’s one of the fascinating areas of research on this whole subject.
OK…but why aren’t all Colorado residents skinny?
So, you would think that if altitude suppresses appetite, it increases metabolism, that everyone in Colorado would be skinny. Well, in fact, Colorado is the leanest state in the country. The obesity rate in Colorado is growing but it’s still about 22% whereas the national average is 42% and it’s the only state with under 25% obesity rate. Not only that but if you stratify Colorado by altitude, the people in the very highest counties are the most slender. I should say the least obese. And you can see that multiple studies even around the world that there’s an altitude gradation effect. The higher the altitude, the less obesity. The reasons for it aren’t entirely clear. We talked about increasing metabolism, decreasing appetite. Those are the most important, but also people who live in these communities tend to take better care of themselves. They tend to go outdoors more. They tend to exercise more and there is very good evidence that if you really want to try to use high altitude for losing weight, the best thing to do is to combine it with exercise as well.
I’ve heard of elite athletes using altitude tents to increase their performance; why have I never heard of altitude simulation for weight-loss?
You may have heard of elite athletes using these altitude simulation devices or tents, and they all do. All the aerobic athletes, all the Olympic athletes use them. These are for different purposes because they stimulate more red blood cell production which is basically like blood doping. More red cells can improve your performance at lower altitudes. You may not have heard though about using these devices for weight loss because it’s such a new phenomenon. Only in last few years has it really been studied for that purpose but you’re going to be hearing more and more about it. It’s safe, it’s effective, there are no real side effects like there is with medications, and let’s face it, obesity is a huge problem in our country and around the world without much in the way of effective therapy. There’s certainly a role for hypoxic devices for simulating an altitude in order to lose weight and for more research in this area.
Can you tell us a bit about altitude sickness and how I might avoid it when mountaineering or high-altitude recreating?
Altitude sickness is a big problem and people coming to visit in Colorado and other high altitude locations is extremely common. Over 25% of people coming to ski in Colorado get altitude sickness. But fortunately, it’s pretty minor. It feels like a bad hangover, headache, not a good night’s sleep, decreased appetite, sometimes even nausea and vomiting, and lethargy. Does that sound familiar? It sounds to me a lot like a hangover and it can ruin your holiday. If you’ve only come in for four or five days and one or two days is spent in that kind of condition, it can really ruin a trip so it’s important to prevent it. One of the ways to prevent it is to use these altitude tents before you come to high altitudes. And more and more climbers are doing this so they could spend less time on the mountain. The technique is to sleep every night at a gradually increasing altitude starting at 6,000 or 8,000 feet, going all the way up to 18,000 feet which is where the highest base camps are over a period of 2-4 weeks, sometimes even longer. And what that does is dramatically speed up your acclimatization process when you go into the mountains so that you don’t get altitude sickness. You don’t have to spend as much time acclimatizing, and you can go a little bit faster. So, these devices can be used to help prevent altitude sickness.
What’s more effective for improving cardio: Live High Train Low (LHTL) or Intermittent Hypoxic Exposure (IHE)?
In addition to using these devices for weight control, they can also be used for improving cardiovascular fitness and even improving exercise performance. There’re a couple different techniques for athletes. Live High Train Low has been shown to be the most effective and it’s the most popular. That’s where athletes live at high altitude; that is, they spend most of the day at high altitude, but then go to a lower altitude to train because they can train more intensely at a lower altitude than they can at high altitude. That’s called Live High Train Low.
Another technique is Intermittent Hypoxic Exposure where inside a hypoxic tent, or with a hypoxic mask, a person exercises while they’re hypoxic for say an hour at a time or 30 minutes at a time or even up to 90 minutes at a time. That technique has not been shown to be as successful as the Live High Train Low technique.
Is it safe for my partner to sleep in the tent with me? How about my dog?
Sure, you can have other people sleep in the tent with you, but if they’re not acclimatized, if they haven’t been adjusting to it over a period of time, they might get a headache or have a poor night’s sleep. So ideally, anybody who wants to sleep with you in that tent should have a gradual exposure and gradually increasing the altitude just like you’re going to do. Dogs and pets can also feel the altitude and they can sometimes get a little lethargic, a little bit sick, but they also adjust very quickly.
How is simulated altitude different to actual altitude and does the body respond differently?
Simulated altitude and actual altitude are a little bit different. Actual altitude is a little more stressful on the body. It induces more physiologic changes than simulated altitude. For simulated altitude, you don’t change the pressure, you just change the concentration of oxygen in the air. You add nitrogen, and that reduces the oxygen level and that’s the same as going up in altitude in terms of the amount of oxygen available to the body. Obviously, simulated altitude has a lot of advantages. You don’t have to travel; you can do it at home if you have a small tent device or deoxygenated room for example and you can go in and out, there’s no chamber lock so there’s no change in pressure. It’s much simpler than having an actual altitude chamber.
Is it harmful for me to go from 12,000 feet to sea level and back again (for example, if I have to get up to go to the bathroom in the middle of the night)?
So, you might be going from 12,000 feet down to sea level then back in the device at 12,000 feet. You might expect that to have some detrimental effects but it seems to work out pretty well. Again, there’s no change in pressure it’s only the change in the oxygen concentration. But the body tolerates that very well since you’ve been sleeping at 10,000 or 12,000 feet simulated altitude for a number of days so going out for a brief period of time, coming back in it’s not going to make much difference. It’d be the same as putting on an oxygen mask for a few minutes and then taking it off again and one doesn’t have to worry too much about the effects on the body of going back and forth like that.
What are the contraindications to simulated altitude therapy? Who should not sleep at altitude?
So, like any therapeutic advance in medicine, there’re indications and contraindications or what we call relative contraindications. Before someone is going to use a hypoxic device to simulate altitude in order to lose weight or improve physical performance, they really ought to be cleared by their physician to make sure they don’t have any issues that could come up or that could be aggravated because of the low oxygen exposure. For example, blood pressure that’s under poor control would be a relative contraindication. People who have sleep apnea and have to use a CPAP device or oxygen during sleep obviously are not candidates for this kind of treatment. But most people who are overweight, but otherwise healthy can do okay. Diabetes is not an issue. Lung disease could be an issue so check with your doctor if you have lung disease before going to a simulated altitude. There aren’t many contraindications to the use of these kinds of devices, but lung disease, heart disease, poorly controlled blood pressure, seizure disorder, a few neurologic conditions. Overall, it’s a good idea to check with your doctor before using these kinds of devices or contacting a high-altitude medicine specialist.
Thank you so much for your time and expertise, Dr. Hackett!
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