Saturday 21 April 2007

Pic of the day: "I am a wife so I don't need things like going out to play." Let us assume she is talking about housework and such, which is indeed a perfectly acceptable way to stay in shape. (Albeit more boring than play, I suspect, unless you are severely newlywed.)

Weight and health

I know I risk repeating myself here, but on the other hand this topic is of great interest to millions of people. (Unfortunately for them, millions of people don't read the Chaos Node, but even a trickle helps in the desert.)

A problem is that we grew up learning the wrong things. Another problem is that tabloids print quick news that don't create a clear picture of what we know today. A third problem is that people who profit on your fears will feed you lies to take your money from you. I have none of these drawbacks. There are things I don't know, but I am pretty good at sorting the wild speculations from valid research. No doubt science will unearth more facts over time. If I am still around, I intend to comment on them. But for now, an overview about weight and health, and things closely related to them both.

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Weight and health both depend on genes, environment, dumb luck... and lifestyle choices. Specifically, they both depend on what you eat (and how much), and how physically active you are. There is little to do about the genes, but a lot to do about the last two factors.

There is no universal "tipping point" which will take you from "damned" to "saved". There are certain milestones though. The closest we come to the fabled health salvation is the practice of at least light exercise half an hour a day (or one hour every other day if you so prefer). If you don't do this, you better have excessively healthy genes. This seems to be a vital signal to the body that it is still inhabited, so to speak, and should not yet start decomposing. OK, that's a bit flippant. What it does seem to do is cause the body to handle sugar and fat differently from before. The amount of free fat in the blood sinks, and the muscles are more likely to burn fat rather than sugar with the same amount of work. (They will still burn sugar if they are in a hurry, as sugar is faster to process and the job can be started before oxygen arrives.)

In fact, the latest research shows that physical activity is far more important than diet. Unless your food is extreme in some way, it will have little effect on your lifespan. There is less risk of some cancers, especially in the colon, if you eat lot of green leafy vegetables, and perhaps a little if you eat fruit. In comparison, being physically active has dramatic benefits for blood pressure, cholesterol and triglyceride balance, and the risk of having a heart infarct, not to mention surviving if you have one after all.

The activity needs to be continuous but there is little benefit in training hard. If you are on the verge of breathing hard, but not necessarily doing it, that is enough. For a person of normal weight this would mean for instance brisk walking with some jogging now and then in flat terrain or some walking uphill. If you are in good shape, you may need to jog most of the time. If you are obese or nearly so, simply walking might be enough to gain the same degree of exercise. It doesn't hurt to run or swim and get exhausted and panting (unless you have or are close to having heart problems already – consult your doctor if in doubt). But the important part is to keep up the exercise several days a week for months on end.

(Even if you run, you still have to keep it up for about half an hour. You cannot run for ten minutes and then tell yourself "it would have been at least half an hour if I had walked". Your mind may believe it, but your body does not. Likewise it seems the exercise must be continuous or nearly so. If you walk ten minutes each hour for twelve hours a day, you will have spent four times as many calories, but still not triggered that special reaction that changes the fat balance in your blood. I am not sure exactly how long pauses you can take, though. Probably only till your heart rate returns to normal levels, which is not long for the first half hour.)

This advice is for those who simply wants to avoid a pointless early death with as little waste of time and energy as possible. It will not necessarily make you look good in a swimsuit. As I said, it is perfectly possible to be fat and exercise. In fact, just taking a long walk may be good exercise if you are fat. But you will still be fat when you come home. And half an hour a day of walking can easily be compensated by a goodly piece of chocolate cake. Even if you don't, you will probably lose fat so slowly that nobody will notice until your high school reunion.

It is possible to be overweight, even moderately obese, and healthy. But people will still snicker at your plush posterior and independently moving tummy. I don't know why this should bother you. Then again I don't have a plush posterior, or even a beer belly, so what do I know? But if you want to be slim, obviously more desperate measures are required than if you just want to hang on to life. This is where diet comes into play.

The cruel truth is that some diets that produce weight loss are downright unhealthy. This includes the Atkins diet, which admittedly has some healthy parts (veggies) but way too much fat. Due to the way our body regulates appetite, eating fat may actually be a way to lose weight if you are fat. (Not if you are already lean and want to go further down, though.) But the extra fat increases the risk of atherosclerosis, a leading cause of death. You better remember to keep moving if you go down that path. There are also various protein diets, which are also bad. The body burns sugars, starches and even fat cleanly, leaving nothing but carbon dioxide and water. Proteins, however, leave a toxic residue that the kidneys have to get rid of. If you eat lots of protein, you must either drink plenty of water (generally a good thing) or risk toxic build-up or damage to your kidneys. This concern does not apply to sugar, starches or fat at all. You can gorge on them till you die and your kidneys will generally not care.

If you want a muscular body (without illegal drugs) you should do strength training. This is entirely different and separate from the "heart training" of long but light exercise. Strength training is all about bursts and straining your muscles as far as you can without hurting them. (This varies with age and previous training. Again, talk to an expert.) In addition to looking good on the beach (unless you overdo it) the extra muscle mass burns some fat on its own even when you are not training. This is the nature of muscle mass, it requires some upkeep even when not in active use. On the other hand, muscle tissue is heavier than fat, so your weight may not go down as much as you expect.

At the other end of the rainbow, there are those who dedicate their lives to living as long as possible. The most extreme case is what we call "caloric restriction", in which you eat only two thirds of normal daily need for years on end. This causes the body to go into a permanent state of starvation, shutting down unnecessary processes such as the reproductive system, and producing less heat. Experiments on a wide range of animals show that this prolongs the life, sometimes with 50%. The older individuals also stay young longer and are less prone to cancer. It is unclear how much the process will influence thinking in humans, who devote far less of their daily calorie intake to the brain than the species we have tested on so far. It seems likely that the brain will also function more slowly, but only a few volunteers have so far chronicled the experience for themselves. They seem to retain most of their intellect, but as mentioned above they lose all interest in sex. I like that priority, but not the thought of living in constant starvation. Obviously it requires an extraordinary strength of will.

Less drastic but still rare is the Dean Ornish lifestyle change, also recommended by Ray Kurzweil. In addition to the daily exercise, it requires you to only get 10% of basic daily calorie needs from fat. Since fat gives twice as many calories per gram as carbohydrates and protein, this means only 5% - one part in twenty – of your dry food can be fat. This is if you live a quiet life. If you have hard physical work or plenty of exercise, you will have to add some more fat. But for an average man with an office job, only 250 kcal a day in the form of fat. This pretty much requires you to be a vegetarian, as even lean meat has some fat in it. You would end up eating so little meat each day that it would hardly be worthwhile making a meat dinner. I suppose you could have a lunch meat sandwich or something though.

The Ornish diet, combined with daily light exercise and regular meditation, is proved to actually reverse the fatty plaques on your arteries. Not a hoax. But the people who are able to stick with it without living in a special dedicated community is so small as to not influence statistics. You could probably learn the name of every one of them. Instincts and popular culture conspire to pry people away pretty quickly if they try it on their own. And of course, you might still get run over by a bus.

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To sum it up: Being fat is less dangerous than we thought, it is the lack of physical activity that kills. Of course, the two tend to go together: It is uncomfortable for the truly obese to move around for long, and conversely if they do it anyway, they will probably start losing weight.

Diets are generally a distraction and a waste of time, unless you intend to drastically change your lifestyle from now on and for the rest of your days. Protein is greatly overrated, unless you are building muscle rapidly. (On the plus side, it actually does make you feel less hungry. I have tried. Still, use with caution.)

But fruit is still healthy! Well, unless it is sprayed...