A few years ago I wrote this post on high altitude flatulence expulsion (HAFE). To this day, it continues to get the most hits by far on my site (81.4% of hits this past week). This tells me two important things about humanity:

We cannot get over our fascination with farts
We still have a lot of questions on the effects of altitude

The second point is what leads me to today's post.

I am currently in my favourite place in the world for 4 glorious weeks. It just so happens that this favourite place sits at 1,800 m (just over 5,900 ft). On any given day we may hike or take a cable car up to 3,500 m (11,500 ft). According to my favourite source of potentially erroneous but easily accessible information, Wikipedia, this places us at 'high' altitude (not 'very high' or 'extreme', which come with their own set of problems).

It's worthwhile to note that other more scholarly articles define 'high' altitude as anything above 2,500 m (8,000 ft). Since I'm no scientist and I've felt the effects sitting as low as 1,500 m, I'll stick with Wikipedia's version for the purpose of this post.

Not everyone will be hit as hard or at all by altitude sickness at these levels, but the visitors we've had at this height tend to support the theory that many will.

Bear in mind that my everyday life normally has me sitting at 10 m (33 ft). Any way you do the math, that's a pretty significant difference in altitude. So it's perfectly normal that I would require some period of adjustment. But since I've been visiting high altitude regions for a few years now, I pretty much know what to expect during acclimatisation, and I know a bit more how to prepare than I did the first time I ventured to 1,500 m. So I thought it only fair to share the wisdom I've gleaned along the way:

Trouble breathing: This is not caused by lower concentration of oxygen levels, but by the increased barometric pressure which allows fewer oxygen molecules to enter with each breath. In order for your body to get enough oxygen, you need to ventilate more, meaning you have to breathe harder. Despite this, the oxygen content in your blood won't quite get up to sea level concentrations, yet you will still require the same amount of oxygen to perform everyday activities. This will lead to the second symptom:
Increased heart rate: Your heart will pump harder in an attempt to get more oxygen flowing via your blood stream to your organs. To give you an idea, my average resting heart rate usually sits somewhere around 55. At 1,800 m it's about 68.
Dehydration and thirst: Your increased respiratory rate, combined with low humidity and dryer air can lead to dehydration at high altitude. At my current altitude, my body is perspiring about twice as much moisture as it was at sea level. Because of lower air pressure, moisture from my skin also evaporates faster.
Headache, nausea, vomiting & loss of appetite: It is quite possible that fluid (blood) distribution in the body will change when you reach high altitudes. This is because your body knows it has to feed your essential organs first (brain, heart and lungs). This means less blood is flowing to your digestive organs, so digestion becomes harder, and more blood being pumped to the arteries to the brain, often contributing to headache.
Sleep disturbances: High altitude can lead to sleep disturbances with frequent awakenings and a feeling of lack of air. At 2,000 m, your body actually feels like it is exercising, so you may not wake up feeling quite as refreshed as you'd expect.
Gas & bloating: Even though the pressure on the outside of your body decreases, the pressure of gas inside your body remains the same. This creates an imbalance and a greater urge to expel gas and relieve the pressure.
Fatigue: Based on the above, your body is likely working harder, you may not be feeding it as much as it's used to, you're not sleeping as well, and you're generally uncomfortable. It's no wonder you're tired!

Thankfully, most of the effects listed above will abate within a few days, and there are a few ways you can help it along.

Rest: Plonk yourself down somewhere comfortable and enjoy the view. Give your body a little break, allowing it to adjust to these new conditions, and don't push yourself too hard for the first few days.
Breathe in that cool, crisp, fresh air: Get outside, go for a short, slow-paced walk, and let the sun beat down on you. Walk a little further every day; you'll be surprised at how much stronger you'll feel within a few days.
Drink, drink, drink: No, NOT alcohol. Drink as much water as you possibly can, and start before ascending. Avoid alcohol and caffeine if you can for the first few days (I need my coffee in the morning, so I just drink extra water to make up for it). Moisturising from the inside out will help with headaches, dry skin and fatigue.
Descend: Go down if you feel your symptoms getting worse. Even 200 m can make a difference. Walk down if you're up for it, or grab a cable car or train if they're available. This can help pump more 02 into your blood stream and really re-energise you.
Ascend: If you're not feeling too bad, go up a bit and then come back down. It may be tough on the way up, but you'll feel revitalised when you get back to lower altitude.
Eat plenty of carbs: Apparently carbs can supply up to 15 percent more energy for the same amount of oxygen in comparison to fats. Don't worry about weight gain; you're burning more energy at heights. Make smart choices, and fuel your body well.
Moisturise: Your skin may feel flaky and dry; dish out for a tub of moisturiser to help hydrate from the outside in.
Protect yourself from the sun: I live in the Middle East, so you'd think I'd be tan as a nut, but that isn't the case. Many days it's too hot to go out, and when the weather is milder there tends to be a thin film of dust in the air that dilutes the effects of the sun's rays. So when you get me 1,800 m closer to the sun on a cloud-free day, you'd better believe I slather on sunscreen, wear a hat and sunglasses and wear long sleeves and pants.

Did I mention 'REST'?: Within a few days, you will likely have acclimatised, but I find that the sleep disturbances persist. Since I'm on vacation, I allow myself an afternoon nap after a vigorous walk if my body's telling me it's tired. I love to spend the day hiking, skiing and exploring, but evenings are devoted to relaxing on a patio sipping local wine, reading to my heart's content, making puzzles, playing board games and watching movies. You only live once; go easy on yourself!

Once you get over the physical symptoms of high altitudes, you may find yourself feeling more energised. You'll be amazed at how quickly you can walk uphill again. You'll find yourself itching to get out into the fresh air and active. You'll want to freshen up. If you're like me, you may want to cook up a storm. This is when you'll start to notice other differences at altitude:

Weight: Because you are further from the earth, less gravitational force is actually exerted on your body. This translates into a lower weight on the scale; not much, but measurable (think a quarter kilo ...).
Hair texture: Because there is less moisture in the air, people with curly/frizzy hair may find their hair is a bit straighter at altitude. This may make it appear slightly longer, though there is no scientific evidence to show that hair actually grows faster or slower at altitude.
Boiling point: Because boiling water relies on both heat and atmospheric pressure, water will boil at a lower temperature at altitude. This will mean that you may have to cook you veg, rice, or pasta for a little longer to experience the same 'doneness' you would get at sea level (boiling point at sea level = 100C, boiling point at 600 m = 98C.
Cooking in general: Things will take longer to cook. Think eggs and meat. Don't turn up the heat, this will only burn them. Just cook them a little longer. Lesson learned, this may mean meat will end up a bit drier than you're used to. Word to the wise: if you're an amateur like me, don't ever attempt to whip up egg whites for a meringue at heights. I tried unsuccessfully this morning to whip some up to create beautiful eggs in a basket ... I ended up with a pretty flat and watery egg white omelette.
Taste and smell: Though I haven't personally noticed any difference, there are some people who say they have trouble distinguishing tastes at altitude. God forbid I'd be unable to taste the soothing richness of my morning brew!

This is not an exhaustive list by any means, only me dipping into a few of the symptoms I've experienced at altitudes of 1,500-3,500 m. The symptoms will vary from person to person, and are unlikely to be life-threatening at these heights. But for those of you who, like me, are seeking to escape sea level for a little ski or hiking escapade, it's best to be prepared for the worst so you can face it head on and get on as quickly as possible with what you came here to do in the first place ...