Diet & Health

Don't feed your inner worm!

2010-10-16T20:21:00.000-04:00

One of the most profound insights I got from reading Good Calories, Bad Calories by Gary Taubes concerns the interpretation of cause and effect when considering caloric balance and weight gain. It is a difficult concept to grasp, and I had to think about it a long time before I understood it. I've participated in various comment sections in different blogs and have found that I have not done a good job explaining it, so rather than cluttering the comments in them, I'll expound on it here.

In a nutshell, the idea is this: if one gains weight, then by definition one has taken in more calories than one has expended -- one has "overeaten". That's what thermodynamics tells us. What it doesn't tell us is why one has overeaten. Most people believe -- and it seems obvious by observation -- that overeating causes weight gain. But here is the other possibility: weight gain causes overeating. This might seem silly and perplexing at first, but I propose a thought experiment below to explain the profound difference.

Let's imagine I have been affected with an intestinal parasite, like a tapeworm. This worm lives for itself, and steals some of the food I eat. It is capable of growing to an enormous size, capable of weighing as much as its host, and it has food preferences.

Now suppose this parasite steals ten percent of all the calories I ingest. Over time, I find that I am less satisfied with my portions, because the amounts I am used to eating now leave me hungry. So I have an extra snack or meal. If I had been living happily on an average of 2,000 calories a day, I find that I must now eat 2,200 calories, because the tapeworm has eaten and stored 200 of them to foster its own growth. After 150 days of this, my tapeworm now weighs a pound. The extra 200 calories a day is hardly noticed by me, because it is so easily obtained, and after ten years of living with my tapeworm, it has grown to weigh 20 lbs.

Now poor me, ten years older and 20 lbs. heavier, wonders how I gained this weight, in spite of watching my portions and exercising regularly! "Eat less!" "Exercise more!" say all of my friends, doctor, and the conventional wisdom.

So I cut my portions for a while, and guess what? I lose weight! Yes, my tapeworm slimmed down a bit, as have I, but now I am trying to live on reduced calories, and my worm still takes its (now reduced) tithe of my meals. My metabolism and cells are screaming for fuel by making me hungry. I feel tired and have no will to exercise. I still need my daily 2,000 to function well.

Eventually hunger gives in, and over time I must return to eating 2,200 calories a day, and my worm gets bigger than ever. And again I need even more energy to carry around the extra weight.

Now, knowing that my weight gain is due completely to the pirated and stored calories in my parasitic worm, and inaccessible to my metabolism, would any reasonable person blame my weight gain on my "overeating"? Is my overeating causing my weight gain?

No, the root cause is that the fuel I consume is not all getting to my metabolic engine. It is the weight gain of my parasite that is driving me to overeat. And if I don't overeat, I will become sedentary, or lose lean mass as my body attempts to compensate for the semi-starvation imposed upon it.

Now let's imagine two other conditions: my tapeworm loves, just loves sugars and starches! It will actually eat not 10% but 75% of the sugars I ingest, but it's not so fond of protein and fat. Furthermore, it is triggered to start eating by sensing high insulin levels in its host. Now what kind of diet would be the worst I could eat? What kind of diet would go a long way to fattening my worm, and leave me with the least share of the calories I eat? What kind of diet would ensure that I became really, really hungry not long after eating? I think you know the answer.

If you can now transfer these parasitic qualities to fat tissue itself, you begin to see the idea. Imagine that Metabolic Syndrome is an imbalance in the regulation of the fat tissue itself, causing it to hold on to stored calories more than release them. The end result is the same. The fat tissue has become like a parasite, robbing the rest of the body of the fuel it needs, and the body responds the way it always does, signaling the host to eat by inducing hunger. If that hunger is not met, it will slow down metabolism to compensate for the lack of energy. Fat storage is causing overeating, not the reverse!

If this is indeed the cause, or one possible cause of obesity, it explains several problems that the caloric-balance theory does not. For instance, why caloric restriction and exercise are so ineffective as a long term solution: it does not correct the underlying imbalance.

As far as I know, there has not been enough research done that can actually pin down the cause of the metabolic syndrome. Once you get it though, it may be incurable, and if I go out on a limb here, the best treatment may be a low carbohydrate diet.

I hope the above has made the understanding of the idea of causality in the conservation of energy a little easier -- and thank goodness we know how to treat tapeworm infections!

Guest post: another paleo-diet success story

2010-07-21T11:27:00.000-04:00

Anecdotal evidence continues to mount. Today's post is from a friend who has managed to lose 25 pounds in three months. He is the fourth person in my circle to have successful weight loss with a whole-foods, paleo approach to nutrition. This was originally posted at cavemanforum.com. Thanks, Andy!

This is actually my second kick at the paleo can and, with one exception, it's gone much more smoothly than my first time around. In case anyone out there in Internet-land is as half-witted as I am, here are some basic tips from my go around that may help clarify things so you can get it right sooner.

And of course, I have been getting things wrong and will doubtless continued to do so (it's a gift, really), please revisit this thread as others who are much wiser than I correct me.

1) Don't over-read because you may confused between: the wealth of information, the various ideological camps within the paleo world and what things mean depending upon what you are trying to accomplish: are you trying to lose weight or maintain a particular weight. You also may be talking to someone with completely different goals from you. A 22-year-old who wants to get six-pack abs will have one set of needs rather different from you when you're a 55-year-old who's had two C-sections.

2) Keep it really simple to start: meat plus all the green vegetables you want. Where I made my mistake was treating all meats as equal -- in my first go around, I ate bags of cold cuts and paté, which have their place but lay off them to start. What I tell people is eat steak and all the celery, salad and spinach you want; or, salmon nuked on a plate with California mix veggies.

3) Your reading and people's opinions about what to eat depends in part on where you are.

Dairy and fruit in the weight-loss phase are completely different from the post-weight loss phase. There are pitched ideological battles over this but in the weight loss phase, less dairy is better. Now, I got confused by thinking dairy came from cows, cows are animals, ergo it's an animal fat, so I was slathering full-fat tzatziki on all my pork and lamb, and full fat sour cream on all my fish. No, not during the weight loss phase.

4) Nuts, eggs and the like are power foods. During my first paleo attempt I was eating nothing but and there was zero weight loss. I'm not saying never have these but moderate. I also have no natural immunity to nuts. If nuts are in front of me, I will finish the container, no matter how large the container is. It's like Kryptonite, I swear.

5) Add bacon and fish or freshly cooked meats and that unsalted salad spices to salads. This'll help wean you off of salad dressings. (Your taste buds will change, it's true.) Salad dressings I needed to cut in phases in my second go around. During my first go, I went through them by the vat but they're full of crap. Beware of fake bacon bits, too. Also consider buying fresh dill or coriander to scissor into your salads. These taste even stronger than any salad dressing.

Salads don't have to be complicated to be good.* When I restarted paleo, I bought many, many salad dressings. Well, after two or so months, they stopped being used. In fact, they're doing nothing but sitting in the back of the icebox for when guests come over. (By the way, a lot of them have sugar!)

6) In my first kick at the can, I found it hard to understand how the diet caused my lack of hunger. It works like this:

Animal fat keeps you from getting hungry -- particularly if you're overloading yourself with cheese as I was. With the amount of brie and nuts I was eating, my poo became frankly evil. Now that I eat no dairy apart for whitening my morning coffee, I've definitely started answering the second of nature's calls less because I'm getting my fats from freshly-cooked meats. Having fat in the meats keeps you from getting hungry.

That's normal so don't freak as is going 3/4 of a day without feeling peckish.**

By the way, if George Foreman has 'knocked the fat out,' why isn't he thin?

7) Fruits I also overdid when trying paleo for the first time. Again, your taste buds will change and remember that the weight loss phase is different from the maintenance phase. You can track down these nigh-religious debates over fruit in paleo discussion fora. Take home point: sweet fruits may slow your weight loss but if you've been having grapefruit for breakfast for the last 20 years and nothing short of Martians coming and kidnapping all of the grapefruit trees will stop you from doing so, dig in.

8 ) Get a crock pot.

9) Follow 80/20 rule to start. You will make mistakes, but if generally if you're doing 80 per cent of it right, you're going in the right direction. Staying at 80/20 to start rather than 'getting religion' and trying to stay at 100 per cent paleo to start will allow you time to experiment, and develop tastes. You're not a machine, you're a person with psychological quirks.

I deliberately gave myself open meals in the first month or two, and just...stopped. I found I could go a lot more toward the paleo side more quickly than I imagined. You may differ.

I once had an e-mail from someone who told me that I might as well not bother doing anything in paleo since I have cream in my morning coffee. That's elevating this nutritional plan to a religion. I mentioned to the same person (or was it someone else) that I also chew gum. Well, my goodness, it was like saying 'I'm a Nazi' to this one paleo practitioner. Since cavemen didn't chew gum, I wasn't on the diet therefore I should go to MacDonald's this instant.

Look, the point of eating this way, at this stage of the game, is to lose weight (another 25 lbs to go!) not adhere strictly to one person's strict interpretation of edge case items. Thog and Urg the cavemen also didn't drink Perrier or fizzy water but since my practical goal is weight loss, at this stage of the game the strictest possible interpretation of paleo is frankly 'paleo-ism' if I may coin a term.

Some discussions and articles flip freely between what foods mean in the weight loss phase, versus the maintenance phase because the authors themselves are confused or because they're answering an issue that's unrelated to your weight loss/maintenance status. Some people deal with edge cases and core foods the same way. People who do so can be well-meaning but cause you short term confusion. However, once things become clearer in your mind thanks to experience, you can have quite a lot of fun yanking their chains because they don't typically have senses of humour. If you're confused about what's nutrition/opinion or ideology, ask yourself if it fits within the 80/20 rule when explaining it to a really smart friend who doesn't know anything about this subject -- and relax.

QD

*They also don't have to involve cutting tomatoes, which I regard as an imbecillic waste of time but that's just me.
**You'll also miss farting, one of the true pleasures of life but no diet is perfect.

A real scare, and a dietary scare within

2010-06-02T13:07:00.000-04:00

An article in the newspaper today reports on a minor school bus accident where luckily all the children were unharmed. However, my nutrition awareness caused me to trip over this:

"Our staff got the children off the bus, stopped traffic and took them into the school and gave them cookies and juice," said Shawn O'Donnell, head of the school.

The bus driver was quite shaken up and worried about the children's welfare, O'Donnell said.

The accident aside, I would also worry about my child's welfare if strangers were feeding them "cookies and juice"! Once again I'm reminded that such unhealthy choices are deeply ingrained as comfort foods in our culture. As long as kids grow up thinking these things are normal, I fear that we'll never get a handle on obesity and diabetes.

Fat gets the blame again, part II

2010-04-09T11:24:00.000-04:00

Two recent articles once again the reveal the bias toward dietary fat. In a Globe and Mail article, I learned something that surprised me:

India has the world's biggest sweet tooth. It consumes more sugar than any other country on the planet thanks to a healthy appetite for sweets, a widespread use of sugar in mainstay dishes and a taste for cavity-inducing chai (tea).

(I thought perhaps the U.S. was a larger consumer of sugar, but according to the Sugar Association Inc., sugar has been mostly replaced by HFCS, so one "can't blame sugar for obesity". That's an astonishing conclusion, since the two products are chemically similar! This is like a tobacco company saying, "Don't blame us for lung cancer, our competition has been outselling us by a wide margin!")

But back to India, where we learn from a report from the BBC that diabetes rates are out of control. Do you wonder what might be causing it?

Part of the blame falls on the adoption of a more Western lifestyle, involving fatty food and too little exercise.

That's right, diabetes, a disease of glucose (blood sugar) metabolism, is caused in part by dietary fat intake! Once again the evidence is right in front of their eyes and they can't make the connection.

Fat gets the blame again

2010-03-29T14:20:00.000-04:00

There's a new study being thrown around in the media blaming "fatty diets" for forming addictive behaviours in the brain's (actually rat brains) reward system. Here's the link to Nature Neuroscience.

So here's the diet the rats got addicted to: "The cafeteria diet consisted of bacon, sausage, cheesecake, pound cake, frosting and chocolate..."

This is also a very high sugar diet! Again fat gets the blame and sugar gets a pass.

It's known that low-carbohydrate/high-fat diets work well for weight loss -- even when unrestricted in calories. The mainstream explanation for this is that the diets are so restrictive in food choices that people voluntarily eat less because they get bored with the food, and create a caloric deficit.

So why is a fatty diet so boring in one case (bacon!) and addictive (cheesecake!) in another?

Good ol' parsnips

2010-01-03T15:32:00.000-05:00

It's amazing how a diet of whole foods had changed my taste. After being off processed foods, and avoiding sugar like poison for two years, some things I never liked have somehow become palatable.

So yesterday, after a few moments' deliberation, a bag of parsnips joined the carrots in the grocery cart. Since I am not an adventurous cook, I simply boiled the lot for twenty minutes. Today I had some as a side dish to my fatty pork roast.

To my surprise, parsnips are sweet and delicious!

I'm still working up to brussels sprouts and fiddlehead greens.

A hospital snack for diabetics.

2009-09-12T12:33:00.001-04:00

Yesterday I had occasion to wait for a few hours in the emergency at the Montreal General Hospital. During my six-hour wait to see a doctor, I was quite interested to see how things worked.

An elderly gentleman, I'd say about 85 years old, had been admitted, his wife by him. I overheard the E.R. nurse's conversation with him, and overheard that he was diabetic, his current blood glucose being measured at 8.5 mmol/L (153 mg/dL), rather high.

Since the wait was long, he was offered a supper. It came on a tray, with a large strip of paper on it labeled "diabetic".

The supper consisted of:

Vegetable soup
a package of two soda crackers
egg salad sandwich on white bread
three raw baby carrots
fruit salad cup
4 oz. "cranberry cocktail"

The man had half the soup, left the carrots, and finished the sandwich, fruit and drink. The hospital is giving crackers, white bread, fruit and sugar water to an elderly diabetic! I was pretty well horrified. I asked the wife casually if she didn't think it was odd that they feed sugar-water to a diabetic (12 grams of sugar in the cranberry drink). Her reply was, "I'm sure they know what they're doing."

Not seeing in front of their noses

2009-06-04T14:04:00.000-04:00

There is an article in the L.A. Times concerning the obesity problem particularly in Hispanic children. This quote is key:

Looking more closely at the foods the kids ate, 68% of calories came primarily from soda, desserts, pizza, chips, fruit drinks, fruit juice, processed meats and burgers. About one-fourth of the children went over the maximum intake level of 25% for added sugars.

So, after having seen this, what do you suppose the headline is?

Hispanic children are getting most nutrients, but eating too much fat

Say what? That list clearly implicates sugar as the problem! Unbelievable!

Australian researchers still fret over LDL.

2009-05-16T18:35:00.000-04:00

This report comes from the 17th Obesity conference in Amsterdam. It worries that a long-term low-carbohydrate diet increases LDL cholesterol, in spite of quite a hike in HDL! I thought it was already well known that saturated fat increases both so what's the big surprise here? I don't have the source of the paper, and they don't mention particle size or VLDL measurements.

The presenter, Dr. Clifton, seems very concerned about the modest rise in LDL, but silent on the substantial rise in HDL, which I thought is known to be a much better marker for low CVD risk. Further, he attributes this rise not to the diet, but to the modest weight loss in the study group!

It's hard to tell what's really going on based solely on the news report. One thing I will have to check on is "flow-mediated dilation" (FMD) which is a measure the researchers seem concerned with.

Crème fraîche

2008-10-11T18:11:00.000-04:00

In my quest to add more fat into my diet, I've reconnected with my Ukrainian roots and been eating a lot of sour cream. I found that the Liberté brand is good because it doesn't have a lot of additives. Here is the list of ingredients on the container: milk, cream, skim milk powder, bacterial culture, microbial enzymes.

One day my local Provigo was out of stock on this, so I picked up a Sealtest brand sour cream. This is what that brand lists: milk ingredients, modified corn starch, guar gum, carrageenan, carob gum, sodium citrate, bacterial culture.

My first thought was that, ideally, sour cream should have two ingredients: cream and bacterial culture. Sealtest doesn't even list cream! I wrote to Sealtest and asked them why they add corn starch, because I don't want to eat that on a grain-free diet. Their courteous and timely response was that the starch was a thickening agent which improves the texture, and that every other ingredient has a specific purpose. I forgot to ask what the difference between "milk" and "milk ingredients" is. Well, no thanks, I'll stick to the Liberté brand for now.

Shortly after that exchange, I stumbled upon another Liberté product in a smaller grocery. It is called "crème fraîche" and it lists exactly two ingredients: cream, bacterial culture. Bingo! At 40% fat, this is yummy stuff, great for smothering a piece of fresh fruit, or just having a tablespoon straight. It has the consistency of ice cream, and although it has yogurt culture in it, it's not sour tasting. This stuff is going to be part of my regular fare for a good while, I think.

"Everything" in moderation?

2008-09-28T18:41:00.000-04:00

People like to make the case that humans are omnivores. Now literally, that means "eats everything", but in the textbook sense, it just means we are not strict carnivores or herbivores. We are adapted to eat some vegetation and other animals, not "everything".

To prove this to yourself, imagine being dropped in the wilderness, anywhere on earth away from civilization. I live in Montreal, so I like to take the example of a boreal forest, typical of my latitude.

In the summer, the land around you would be teeming with life, but the greatest portion of it would be unavailable to you: bushes, trees, and grasses -- you couldn't digest maple leaves or pine cones. If you were lucky you might find a few wild berries. If you knew what to look for, you might find some edible roots and herbs. If you were quick enough or smart enough, you might be able to catch a fish or bird, or other wildlife -- in other words, you would face the same challenges as any hunter-gatherer. And you would be eating the very foods your body was designed to eat.

So remember that the omni in omnivore stands for: a preciously small fraction of what we can digest and thrive on. Moderation need not apply to this group of foods. In fact, if restricted to these food choices you could eat as much as you want. This is what our ancestors did, and they did not suffer from obesity and other "diseases of civilization".

When we talk of moderation it's usually in the context of modern (post-agricultural) food, or just things which can make you ill in the short term, like alcohol, or sugary drinks. But then you run into the problem of figuring out what a moderate amount is. Is it two beers a day, or three? One Coke or two? What is a moderate amount of rice or other grain? Of saturated fat? Do we judge by how much we can tolerate in the short term without becoming ill, or is there a long-term risk?

I believe that when an animal eats its natural diet, its portions are moderated and regulated by its body, and the feedback mechanisms which govern hunger and satiety. This is what we observe in nature.

Feed it something it is not adapted to, in sufficient quantity, and it will ultimately get sick. This is what we observe in modern human civilizations.

Night sweats and sweets.

2008-09-28T17:56:00.000-04:00

In the last eighteen months of low-carbohydrate eating, I have completely enjoyed the freedom to eat any amount of food I desire. My experience has shown me that the body does indeed regulate its weight via hunger and satiety signals, but only when consuming the proper diet.

However, my freedom to consume has been abused on occasion. I can remember four times involving birthdays and barbecues, where I really packed in the protein. And each time I paid for that gourmandise in the middle of the night: waking up hot, sweating, and with a rapid pulse.

From what I have learned about our biochemistry on low-carb, I think this makes sense. When insulin levels are kept low, fuel calories cannot be stored, so the body has no choice but to burn them. Thus, the night sweats: you take in extra fuel, the motor runs hotter.

It occurs to me that had I wanted to avoid this midnight punishment for gluttony, there was always an antidote: dessert!

Yes, by ingesting a huge whack of sugar, I could trigger my pancreas to work overtime and flood my bloodstream with insulin. This would have the effect of pushing a large quantity of calories into my fat tissue, and spare me the mild overnight "food fever."

I am ready to believe that our custom of eating sweets at the end of a meal is a direct result of this phenomenon experienced by our ancestors. If one is fortunate enough to have a lot of extra food and access to sugar (the combination of which, about a hundred years ago was available only to the wealthy) it sounds like the perfect fattening plan. Now, I don't know if this is a biological "just-so story", but it makes sense to me.

Putting two and two together?

2008-09-19T12:59:00.000-04:00

I came across two articles in the same issue of The Peninsula, Qatar's English language daily.

In the first, we read that Qatar is no different from almost every other modern country in becoming alarmed at the national obesity rates [full article]:

"Around 40 percent of school children in Qatar are obese, according to Dr Mahmoud Al Zari, Director of Diabetes and Endocrinology at Hamad Medical Corporation..."

In the second, they are pleased to report a confectioners' trade show [full article]:

"Qatar has developed quite a sweet tooth as data show the market for sweets and confectionery grew by 23 percent in 2007, just behind Saudi Arabia, which registered a 24 percent increase."

Here is another case where we see increases in obesity alongside increases in sugar consumption. So what does the first article conclude?

"Bad foods are those with high fat content. Fatty foods cause heart burn and acid reflux."

Well, that's zero out of two correct.

Understanding Gary Taubes' ideas on obesity.

2008-02-22T23:05:00.000-05:00

In his book Good Calories, Bad Calories and in some lectures Gary Taubes offers an alternative hypothesis about how and why we get fat. I have read the book, and some of the chapters several times, in an effort to understand the explanation of caloric balance and the conservation of energy. I think I finally get it. However, up until recently I have had a lot of difficulty explaining it to others. I invite you to follow along below, in the hope that at the end you will "get it" too.

In the beginning of his lecture at Stevens Institute of Technology, Taubes' invites the audience to think like scientists as he takes them on a tour of the observational data about obesity from a century ago to present. In this article I want to you to think not so much as a scientist, but more as an engineer.

To do this we are going to examine a very simple model a fluid supply system. The design goal is to supply a small but fairly stable supply at the output, so that irregular supplies at the input won't disturb the flow too much. Think of a car engine idling: a small trickle of fuel must be available at all times. The basic design idea is a storage tank, with a source and drain, and some way of monitoring the supply so we know when to fill it again.

Before we go further, let's take a look at a couple of water supply systems I have seen, one at a friend's country chalet and another at my family's old lakeside cottage. At the first, there was no electricity, and gasoline and propane were common fuels. Here is what was built to supply lake water to the house for showering, dish washing, and toilet flushing.

A small gasoline-powered pump takes water from the lake and pushes it up into the water tank on a platform tower. From the water reservoir, a supply line feeds back down to the household plumbing. When a tap is opened in the house, the water pressure supplied by gravity determines the flow rate. Now here is the clever part: a second little supply line goes back to the pump which can activate the on-off switch. The switch is pressure-sensitive. No water actually flows back into the pump, but the pressure can be measured. When the pressure drops below a defined amount, the pump will start. When the pressure rises to the designed maximum, it will turn the pump off. This clever arrangement is known in engineering as a feedback control system. It saves us the trouble of operating the switch manually: we could find a way to read the tank level ourselves and keep it somewhere between full and empty. This is how we attend to our cars; since they don't refuel themselves, their fuel supply relies on the owner to periodically fill it up. They rely on the visual feedback of the fuel gauge.

You may wonder why we bother with the trouble to construct a platform and tank. Why not connect the pump directly to the house supply? Just turn it on whenever you need the water. That's a legitimate design too, and it will work of course, but it makes for very inefficient use of our pump, as in a regular car in city traffic that stopped and restarted the engine at every red light and stop sign (the design of modern hybrid engines attempt to reduce that inefficiency).

Our pump is extremely over-powered for the typical flow we'd need in the house; probably hundreds of litres in a few minutes, so it makes sense to use the pump sparingly. It can replenish the tank quickly compared to our household usage, so it won't run as often, but it will run efficiently.

In this tower reservoir system, there are various things that the engineer will have to consider, such as the flow capacity of the pump, the diameter of the fill hose, the height of the tank (the level of the water above ground is called the"head"), the capacity of the tank, and the size of the house supply hose. Another critical setting is the regulation of the pump's pressure switch: it will determine the variation in the head. All of these things will determine the flow rate of the water at the tap. Later we'll see how adjusting these design variables affects the output.

In this system it will be near impossible to keep the flow exact, but we can design for an acceptable minimum and maximum. When it is working correctly, on average the tank will be partially full, and the variation in the head will determine the variation in flow at the tap. In order to understand this system, you must convince yourself that these two things are linked.

Here is a small experiment you can do at home. Get a plastic bottle or cardboard milk carton, and punch a small hole on the side, close to the bottom. Set it at the edge of the sink, and then fill it up (of course leaving the cap off). If you have managed to get a fairly clean round hole, the water will stream out of the bottle in a nice parabolic curve, very familiar to most beer-loving engineers. Watch where the stream hits the sink bottom. As the level in the bottle goes down, the stream will get weaker, on the point where the stream lands in sink will get closer to the bottle. This should convince you that pressure is directly in proportion to the level of the water. More important, you should also see that the amount of water, the rate of outflow, also lessens with reduced pressure. You can also play with the size of the hole: obviously a smaller one restricts the flow more than a larger one, but here is a key point to remember: the pressure from the head (the water level) is the same regardless of the hole size.

Another thing to notice is that the size of the bottle does not affect the pressure. You could have a milk carton or a five gallon jug, but with the same size hole, the pressure is the same, and the arc of the stream will be the same. What does change is how much time will pass before it empties, as the pressure will fall more slowly with a larger bottle.

A variation of supply design existed at my old country house, where we had electricity but no running water. In this case, another option was available, a small electric pump with a metal compression tank attached. This type of tank had a much smaller capacity than the water tower, more like five gallons rather than five hundred. It had an internal membrane, like a inner tube in a tire. When the pump filled this small tank, it would compress the air between the inner balloon and the metal. When the pump was off, this air pressure could supply the force needed to push water out and into the house. The benefits of this system is the size, so this unit could be installed in a small pump house, was quieter, and could be installed closer to the taps. Ours was located under the cottage in a crawlspace. One of the main differences in this design is that the pump runs much more frequently, but electric pumps have different efficiencies than gas ones. For the same reasons, modern hybrid cars run better on electricity in stop-and-go traffic, whereas a gasoline engine performs best for longer steady runs like on the highway. As before, there was an automatic pressure switch to control the operation of the pump to keep the tank pressure within the desired range.

Now most engineers know that all the variables in these water pumping systems have analogous ones in other situations. An electrical engineer would recognize this as the periodic charging and discharging of a capacitor or battery. The common person recognizes this as the charging of a cell phone once a day -- the lake is the house AC, the pump is the AC adapter, the battery is the storage tank, and the tap is the electrical drain on the battery. A civil engineer would recognize this in any dynamic feedback system; the lay person might see this as a space heater in a room: again the lake is house current, the pump is the heating element, the tank is the radiator (or the air in the room if none), the thermostat sends the feedback signal to the heater, and the tap is the loss of heat through an open window or through the imperfect insulation. A biochemist might see this as the movement of a molecules across a membrane, where the lake is the organism's food, the tank is the concentration of the nutrient solution in a cell, the pump is osmotic pressure and the feedback is a hormone which controls the channels ("holes") in the membrane. The mathematics of all these things turns out to be the same. I chose to use the water/fuel pump example to illustrate the system dynamics because I think it is the easiest to visualize.

For our discussion, imagine we have a supply system like the one with the compression tank as above. Let's remove the outer metal shell and replace it with a big stretchy rubber bladder, a special balloon. As this bladder/tank fills we can observe its size easily. Remember that our design goal was to provide a regulated output, so we are going to keep the tap open, like the hole in the milk carton at the edge of the sink. As another change, instead of the bladder pressure controlling the pump, let us put a device at the tap to measure the flow, set it to signal at a certain range, and send that signal back to the pump.

Let's watch this system operate in our imaginations, starting from an an empty system. The flow meter will read below minimum, so it will send a signal to start the pump. Very shortly, some water will start coming out of the tap, and some will start to fill the bladder. Since our pump can move much more water than our tap can drain, the bladder will continue to expand. At a certain point, the flow meter will show that it is at maximum, and send a signal to stop the pump. At this point the bladder will be at its largest size, and highest pressure. As the water slowly drains out the tap, pushed by the pressure in the bladder, the bladder will start to shrink. But it will never empty completely, because when the pressure drops enough, the flow reduces and the pump will start the cycle again. After the initial start, the system will reach a state of cyclic regularity, what is called dynamic equilibrium. The pump will cycle at regular intervals, and the bladder will expand and contract. It would appear as if it were breathing, or as a heart pumping, although very slowly.

If we subvert the feedback mechanism manually, what happens? Let's say we run the pump a little too long occasionally, or a little less. As long as the average intake is the same, our system will stabilize itself. In the case of over-pumping, the bladder will stretch, and our output will remain at a high flow longer than usual until things settle down. If we let the feedback system function, all will be in balance.

Now we're ready to look at some of the ways the different components can affect operation. Here are some things that we may observe:

pump runs too hot
pump cycles too often
bladder expansion and contraction is too great or little
average bladder size is too big or too small
output flow varies too much
output flow average is too high or too low

Of all these possible problems, I want to look at one in particular, which is the bladder being a different size than our operating specification. Remember our bottle-over-the-sink experiment: when the hole is small, the flow is reduced. There are two ways to change the design here: we can either enlarge the hole, or increase the head. In our water tower example, if we install a smaller diameter pipe to the house, we would have to keep our water level higher, by pumping more initially, putting the same tank on a higher platform. These are familiar trade-offs for engineers. In the compression tank, we could build it to withstand a higher pressure. Finally in our bladder example, we would have to put in a higher pressure skin if we want to keep its operating size the same, or else we would have to allow room for extra expansion and capacity. And of course we would not want to install a pump so powerful that it could explode our bladder!

Let's watch our system running again, but this time, in the laboratory of our minds, we are going to put a wider pipe between the bladder and the flow meter. On this pipe we'll put a valve so that we can control the output flow from fully open to fully shut. By adjusting this valve setting we can watch the system. First we'll close it a bit. As usual, the output flow will reduce and the the pump will start. The bladder will expand until it reaches a higher pressure, and then the pump will stop. Once this new plateau is reached our system settles down as before: same pump cycle, same pressure variation (but higher average pressure) in the bladder, same output flow. Similarly, if we open our control valve, flow is increased temporarily. The bladder will contract, and push out its excess water. During this time, the pump will be off longer than usual, but once again, after an adjustment period the system will stabilize around the desired flow. You can seen how the size of the output pipe directly affects what kind of storage tank can be used. If we play with the valve settings, we can "tune" our tank for an optimum size/pressure trade-off. This could be important depending on the application. In our water tower example we could design a huge tank. In a car, which carries around its own fuel, you have to be concerned about the weight of the fuel and the size of the tank (this is critical in airplane design). In hydrogen fuel car prototypes, the size of the tank has been a major engineering problem, certainly not the weight of the fuel. There are always trade-offs.

Now let's imagine two identical pumping systems out in the field: same pumps, bladders, pipes and output flow needs (but no valve, it was used in the lab as a design aid, and is not necessary in production models). We install these two systems, and let them run merrily away in their feedback-regulated stable environments. The pumps cycle, the bladders expand and contract, the output flow is regulated as required. They are fuel pumps bringing a steady supply to a complex system of engines which need a regulated fuel supply in order to function.

Now, unfortunately, one of our systems has a little problem. In the same place where our lab valve was, a bit of corrosion and rust begins to build. Over five years, the rust builds up ever so slowly, until the pipe is half-blocked. As we learned from our lab, the system still functions perfectly because our super-stretchy bladder has expanded over time to compensate for this reduced output flow.

We are now going to play metaphorical god and give life and consciousness to our two pumping systems, Arnold Dogma and his poor inflated friend, Rusty Taubes.

Arnold: "Whoa, dude, you're carrying a bit of extra weight, aren't you?"

Rusty: "Cripes yeah. Why am I fat, Arnold?"

Arnold: "Well, I hate to say it, Rusty, but you just eat too much -- you run your pump too often!"

A few days later Rusty says, "You know Arnie, I don't think I pump any more than you do. Look at our cycle times, they're identical." "Trust me, Rusty," says Arnold. "You're fooling yourself, or you're in denial. You must pump more than me, otherwise you wouldn't be fat. That's the first law of thermodynamics. You know that signal you get to pump? Just ignore it once in a while. You'll slim down. Just don't pump so much."

So Rusty tries this. A few days later his bladder has indeed gotten smaller! He continues for a few more weeks like this and slims down more. Meanwhile, the more he slims, the more frequent that pump signal stays on, and for longer periods of time. Finally Rusty gives in to the signal, runs his pump, balloons to his previous size and the output flow is reestablished.

"Geez, Arnie, I tried hard, but that signal was so incessant. What else can I try?"

The naive Arnie says, "Here is something else you can try. You can have them run more engines at your tailpipe, just spend more fuel than you take in! You've got to waste some fuel. That'll slim you right down!" "But Arnie, look at our outputs, they're the same!" protests Rusty. "My flow is the same as yours and I fuel the same kind of engines. We both take in and put out the same amounts. But me -- I'm fat!" bemoans the inflated Rusty. But desperate is he, so some of the output gets siphoned off and burned. After a few weeks Rusty says, "Arnie, that's not working either, the important engines have slowed down, there is less of my output available for them since I've been fueling extra stuff. I'm not functioning to spec like this."

"I just don't know any more, Rusty," says Arnold Dogma. "Maybe you were just designed to have a bigger bladder, " he offers. But he still thinks to himself, "That Rusty just pumps too much. Yeah, he must pump when I'm not looking, or at least if he's not lying, he's fooling himself about his intake. Maybe he needs a psychologist."

Fortunately for Rusty Taubes, the problem was eventually fixed. A new output pipe was fitted, proper flow was restored, Rusty's balloon shrunk back to its original size, and he pumped happily ever after.

At this point the fable ends. Astute readers would not forgive me were I not to address Arnold's point about thermodynamics. Arnie was right of course. Over five years, Rusty did pump more. He must have. But the excess gathered so slowly. No tool exists that could have measured so accurately to see a difference in intake between Rusty and Arnie on any given day. Once the problem was fixed, that extra energy was released.

Now this is a very simple fuel supply system, and it cannot represent the human body, which is an incredibly complex machine consisting of dozens of interrelated feedback loops, and has many different fuels available. Before you protest too much, keep in mind that most people consider the human body as an even simpler machine: fuel intake goes in, gets burned, leftovers go to fat storage. This model considers that our output fuel flow is completely variable (which I think is a mistake), and also assumes that human waste has no caloric value.

Our simple feedback pumping system is very simple, yet it explains several observations about real bodies that the simpler model doesn't:

Many people don't continue to gain weight, they tend to plateau. It is like they have a set-point which they maintain. The weight creeps up over the years, and then they stay there. We all know friends and acquaintances that have a certain body type, which they maintain over the years.
Heavy people may not by lying or deluded when they say they eat the same amount as lean people
Fat people can be just as active as well, and hit the gym more that a sedentary lean person, and stay fat
Reducing intake or increasing expenditure does not work in the long run, it tries to consciously subvert the design of the body. The demand for fuel by the body's metabolism can crack the willpower of 95% of the people who use this method. The successful 5% learn to live with hunger and fatigue.
It shows why counting calories doesn't work, the accuracy needed is beyond our perception
It shows how daily fluctuations in intake and expenditure balance out naturally
It does not break any laws of thermodynamics
Obesity is the symptom of an underlying problem, not the cause

Now I'm not saying that fuel release is the only thing can go wrong, but it explains a lot. In a future post I hope to discuss that the human body has more than one type of fuel, and that it is perhaps not the quantity of fuel which is important in regulation but the fuel mixture. In the fable above it might serve to think that Rusty represented only the fat tissue in the body; the fuel is the circulating fatty acids in the bloodstream. We will see that the hormone insulin acts as the signaling mechanism which can start the pump, and also shut off the output, causing the fat stores to expand.