Guest Post: Fat and Simple

By skepticlawyer

[SL: This great piece by our redoubtable admin, Jacques, came up on my facebook news feed this morning, and I thought it deserved wider prominence. Yes, it’s about food and dieting, but gets there by means of a great deal of interesting industrial technology and very cool diagrams. In the meantime, I will be back on deck once I’ve recovered from the extraordinary realisation that I now have a suntan. In Scotland. From Scottish sun.


Originally posted here.

In my trade we commonly mention the truism that “if all you have is a hammer, everything looks like a nail”. I bring this up because I’m about to do what every smart person likes to do: drastically simplify a complex phenomenon.

Specifically: If all you have is systems thinking … everything looks like a system.

Today’s subject is: how do people get fat?

A long, winding discussion of an analogy which may eventually be relevant, in which Control Systems are introduced

One of the great tributaries of systems modelling is control theory, which grew out of the study of steam engine governors.

Suppose you have a steam train. You want it to move at a more or less constant speed. To do so, you need to ensure that the right amount of steam is admitted into the pistons on each stroke.

In comes this elegant act of engineering genius:

Centrifugal Governor at the Science Museum London. picture by Mirko Junge.

What you see here is one of the innovations that made the industrial revolution possible. It’s a “Centrifugal Governor”, and it means that the right amount of steam will get into the pistons on each stroke. So important is this particular invention that it, along with some other clever innovations, is why the unit of power in physics is known as the Watt.

The shaft in the middle is connected to the drive axle of the steam engine through some gearing or chains. As it spins, the brass balls spin around the shaft (hardy har har). As they spin higher and higher, they compress a little pair of arms which, through a lever, adjust a valve on the piston’s steam inlet.

Courtesy of the Wikimedia Commons, the whole mechanism looks a bit like this:

When more steam is let into the pistons, the engine speeds up. The shaft spins faster, the balls rise higher, pushing the lever, which pushes the valve further closed.

The steam rate coming into the engine lowers, the engine slows, the balls spin at a lower height and the valve opens a bit.

After a while, this reaches an approximate equilibrium. But adjusting the gearing, the weight of the brass, the length of the arms, the length of the lever and so forth, it’s possible to use this simple mechanism to select how much speed you want from a steam engine.

This forms a feedback loop:

Feedback loop of centrifugal governor. Train clipart by gazzaPax.

More specifically, a “balancing loop”. A balancing loop pulls the overall system towards some equilibrium when it strays too far in one direction.

Now it’s obvious that I will be talking about control systems a bit more generally in just a second, but before we leave steam trains behind, I have one observation I want you to keep in mind.

The governor ignores the internal state and configuration of the steam engine.

The governor works regardless of how the engine is currently configured. It need not account for the amount of coal in the firebox, the pressure of the steam, the friction of the pistons, the grade of the track, the amount of water on hand, the kind of coal being burnt … these are largely irrelevant. They all disappear because ultimately, all the governor needs to do its job is to observe one output of the system: the speed of the drive axle.

Courtesy again of the Wikimedia Commons, here is a classic example of a control system feedback loop:

In our train analogy, the Controller was the steam valve on the pistons; the System the was the steam engine and the Sensor is the centrifugal device.

This is about the simplest possible system. Happily, it’s also the same shape as the centrifugal governor: a loop with three parts. Simple loops like these can be composed into ever more elaborate systems. Every part of the diagram can be replaced with subsystems, and subsystems of subsystems, until people start staring at bowls of spaghetti and wondering where the sauce is hidden.

The dietary control system

The simplest possible model of weight loss and weight gain is this: weight is affected by calories in minus calories out (strictly I should be talking about joules in versus joules out, but people are used to talking about calories).

Notice that we have two of the elements needed for a control system: we have a System (our body) which can be measured with a Sensor (a scale or the Mark I eyeball). What’s missing is a Controller.

The Controller is us: it’s own own selves. You look at the scale weight or yourself in a mirror, decide it’s no good, and can then change the inputs of the system (what you eat, what you do).

I am not the first to think of this analogy. Probably the best expositor of this way of thinking about the body is John Walker. In his book The Hacker Diet, Walker spends the first section discussing body weight as a control system. In fact, he does such a thorough, readable job of it that I recommend this book to anyone who wants a serious look at the bottom line of weight loss.

But … insulin! Starvation mode! Carbs! Zones! That study I saw written up in the New York Times!

Various authors have come forward in the past few years to say that “calories in minus calories out” is wrong. More subtly, they say it’s too simple. A number of additional mechanisms are then discussed that affect this or that element of body weight. For example:

  • Satiety
  • Fat storage and release
  • Energy system utilisation
  • Hormonal responses

And on and on it goes. Most problematically, these tend to become all-or-nothing Deep Truth About Weight Control.

In a particularly widely-read example, Gary Taubes developed a hypothesis about the relationship between dietary carbohydrates, insulin releases, satiety and fat storage that he thinks accounts for the “real” cause of obesity. Unfortunately it doesn’t quite stand scrutiny from sciency scientists.

I want you to notice something interesting: that while the internal mechanisms of fat storage and release are enormously complex, with hundreds of interacting variables, the inputs and outputs are simple.

You control what you eat and what you do.

Forcing elements

A better diagram for bodyweight control will resemble a great big mess:

All of the hundreds of factors involved in body weight control have an impact. Sometimes quite a significant impact. But not one of these factors can overpower the simple fact that a body can’t burn dietary calories it didn’t receive.

Net calories is, therefore, a forcing element in this system. It is not the only element, but by itself it can force the overall system into a different configuration. And it’s not as though this is hard to prove. Controlled starvation studies have shown it; history has shown it (look at photos of Changi POWs) and — though it distresses me to draw a connection between acute human misery and chronic diseases of abundance — current events in Niger show it.

So final is the forcing power of caloric balance in this system, that we can potentially ignore the entire mess of subsystems in weight control and treat the whole thing as a black box. That is, we can reduce it to the first feedback system diagram above: inputs, controls, system, outputs, sensors. Calories in, calories out, weight and appearance.

Sounds familiar, doesn’t it? Just like the centrifugal governor, caloric balance requires no consideration of the underlying system apart from inputs and outputs. Calories in minus calories out, ultimately, settles the body weight balance.

Psychology and evolution

Obesity is, as I said above, a disease of abundance. It’s a disease of civilisation and particularly of capitalist civilisation, being as it is so spectacularly capable of producing calories far in excess of those required to sustain every human alive.

As Mssrs Penn and Teller observed, that we are alive today is evidence that our ancestors liked two things: “eating and fucking”. Those primeval life forms which did not avidly eat and bonk were replaced by those who did both whenever the opportunity arose. The entire mechanism of fat storage is a quantum leap forward in survivability for higher organisms, presenting as it does the ability to average caloric inputs over time and to decouple the organism from short-term fluctuations in food availability. Without fat storage animals could not have evolved to their current level of complexity, because that complexity imposes a very high cost in calories. And humans are no exception.

Eating and fucking!
Photo from Wikimedia Commons.

So it’s understandable that people don’t want to control their eating. Or rather, it’s understandable that the abstract, long-term promise of weight loss is swamped by a hindbrain screaming “EAT THE CAAAAAAAAKE, ALL OF CAAAAAAAAKE”. Much in the same way that cars pit a visual-motive system adapted to running speed in the African savannah against tons of steel moving at dozens of kilometres per hour between buildings only metres apart, weight control pits us against our own adapted nature.

Nevertheless, we are not automatons. We have higher brain centres, which have evolved to the point where they can exercise abstract reasoning and suppress our instincts. Diet is no exception to this happenstance. Unless you have diminished psychological functioning (been there, done that, got the pills), you are in theory capable of taking this step. You are not a victim: you are a master of your own destiny.

The key to weight control is finding the dietary template that you can stick to for the rest of your life. That will be different for different people. Some folks are happy with calorie counting a la John Walker. Some people are happy with paleo, primal or ketogenic diets. Others swear by zones or low fat and so on.

Worrying about why a diet works for you is irrelevant. That it works and that you can sustain it indefinitely is what matters. If you can sustain a caloric deficit for the time it takes to drop to a healthy weight and then stabilise, then that’s the diet for you. Crash dieting or yo-yo dieting is not OK.

Special Pleading

What about people with thyroid disorders? What about this low metabolism thing? What about … and … also … but!

I say, good fellow, have you considered that Taurus, Gemini and Aries have to overcome the baleful influence of Jupiter in the 4th house?

Every time you point out the simplicity of the net calories model, somebody comes up with special pleading.

I distinguish special pleading from non-caloric causes of obesity because they tend not to be theories about how obesity occurs. Rather, they’re virulent memes which allow us to turn that powerful, higher abstract reasoning onto the path of justifying what our hindbrain wants us to do.

My objection is that very few people have a genuine reason why simple calorie counting won’t work. Very few people. Yet everybody is quick to self-diagnose. “Oh!” they say when they hear the latest health journo blurb. “I must have that condition. I guess I’ll never be able to lose weight. I should just accept it. Pass the gravy, my glass is empty.”

Well look. Maybe you do have Schnitzengrüber Syndrome. But do you know what? You probably don’t. And until you see your doctor and check, you can probably assume that you don’t and that putting the fork down is the bottom line.

And … even if you do have a medical condition which affects your particular biochemical reaction to food or exercise, it doesn’t change that net calories is still a forcing element. People with every metabolic malady known to science, and a few more that aren’t, will have died throughout history through simple starvation. No disease can create energy from nothing.

Self control

One thing I liked about the Hacker Diet is that Walker teaches you how to control yourself. Make frequent measurements and then adjust your system inputs. No need to make dramatic changes, folks. Weigh yourself daily, perhaps take weekly photographs for visual comparison, and gently reduce your calorie intake.

Because you’ve kept the records of weight and appearance, you can see what your metabolic system is doing. Why speculate about how you will respond to food? Measure! Verify! You are a control system.

Caveats and Conclusion

What annoys me about models like Taubes’s is that on the one hand they complicate (“It’s not just calories in minus calories out!”) and then over-simplify (“It’s caaaaaaarrrrrbbsssss!”).

Well, if it please the court: I’m guilty of this too. I’ve simplified enormously. Abstraction is the basis of my profession (software engineering). But that doesn’t change the fact that the model I’ve outlined above is true, by any serious empirical standard. Cut calories enough and you’ll lose weight, add enough and you’ll gain. How much those inputs affect weight and appearance will vary wildly from person to person, but the underlying relationship will always be there.

If you have one, and only one thing that you take away from this screed, it’s this: calories in minus calories out is a forcing element. It will always, in the end, force body weight in one direction or the other.

But there are caveats! Simply bludgeoning the body into submission with help from that pitiless prick, Mr Physics, may be counterproductive. For example, cortisol is a hormone which inter alia mediates fat release. But it also mediates protein breakdown in muscles and the density of bones. Crash dieting tends to kick cortisol up a lot and well, it’s not too picky about what receptors it plugs into. Crash dieting isn’t healthy because as well as losing fat, you can lose muscle protein and bone density also.

Another caveat is mental health. As has been raised by people I’ve argued with on Reddit, depression can affect the will to seek help or the effectiveness of “tough love” advice. And, of course, for some people, calorie counting or crash dieting spirals off into serious health issues such as anorexia, bulimia or (less seriously) orthorexia. In such cases professional help should be sought first of all for the mental health issue. Weight can wait.

So. Here’s the moderated view of what I want you to take away:

  1. Calories in minus calories out is the ultimate, unavoidable arbiter of body weight.
  2. But don’t crash diet. Lose weight gradually over time. Pick a diet you can enjoy and sustain for the rest of your life. There’s lots to have a go at.
  3. Don’t lie to yourself. Keep weight and photo records to know you’re making progress. If you get thoroughly stuck and your records show you’ve been doing it right, see your GP and/or a registered dietitian (not a nutritionist, these are frequently unlicensed quacks) to see if you have something interfering with your metabolism.
  4. Do some exercise, and in particular do some training with weights to prevent muscle and bone weakening.

Patience, friends. Patience and consistency can achieve amazing things. Trust me.


  1. John H.
    Posted May 28, 2012 at 5:13 pm | Permalink

    There are sufficient variations in individual metabolism to make any single solution for all and sundry problematic. Changes can include dietary considerations like foods that impede fat absorption(compounds in coffee, or increase fatty metabolism( ALcaritine), to levels of brown adipose tissue(recent research suggests this can be increased), to variation in PPAR(liver), to CORT etc etc. Hence there are some people who can eat all they like and never get fat, then there are people like myself who have to be very careful about their caloric intake. There is even evidence to suggest that fasting can increase mitochondrial function and thereby reduce total caloric intake requirements. This may relate to autophagy(clearing the crap out of cells) which in turns improves mitochondrial function. Recent research claims that even lack of sleep can promote obesity.

    Another issue that is prevalent in the recent endocrine journals is the presence of obesogens in our foods. These compounds, BPA being a prominent example, appear to impact on PPAR function and thereby promote obesity. To what extent this constitutes a problem in humans is as yet unknown but it is known that levels found in humans do mirror the levels in experiments which induce obesity. There are even some striking studies suggesting these levels, combined with obesity, are major driver of type 2 diabetes. At least one study asserts that the levels of these compounds are more determinative of type 2 than obesity itself. I don’t think this is a major causative factor but it is something we need to keep our eyes on.

    Being overweight, within limits, may not be such a big problem as supposed. Overweight people who good aerobic capacity can be quite healthy, regular exercise may be the critical variable here.

    Nonetheless there is are very good reasons why the medical community is pushing this issue so hard. Obesity consistently correlates with poor health outcomes. The most striking example of this was a paper I read many years ago which found that middle aged obese women had very much accelerated brain aging, this being consistent with obesity increasing systemic inflammation.

    BTW, if you are aggressively losing weight pump up the antioxidant intake because toxins are stored in fat and are released with weight reduction increasing oxidative loading.

    Be practical, if you want to lose weight lose the stimuli the promote eating. Keep food out of sight. I have learned during my fasting periods how sensitive we are to these stimuli, smell something and immediately the stomach starts growling. My stomach is a famous growler because it is typically empty. It is surprisingly how little food one can survive on after practicing fasting for a few years. I now have to take a multi-vit because I know my nutrient intake is way too low … .

  2. Posted May 28, 2012 at 9:44 pm | Permalink

    Great post Jacques!

    But yes, dieting is apparently a controversial issue.

    There is a lot of junk science floating around about weight loss, and beyond ‘calorie in, calorie out’ I have yet to see anything else in the literature which works as a weightless program.

    Things like ‘starvation mode’ or ‘no carbs after 7’ etc are hypothesis that are pretty clearly debunked as tactics for weightloss . That doesn’t mean that the science underlying these programs doesn’t have some merit, it just isn’t helpful health advice.

    One of the biggest misconceptions I think people have is that they can just ‘burn off’ the calories. Not realising that exercise has a limited role in balancing the equation.

    Also, dieting is not a pleasant experience.. even if it is a “lifestyle change” it will still be a less pleasurable one. You will feel hungry and miserable, at least until you are used to the new caloric intake.

  3. Posted May 28, 2012 at 9:45 pm | Permalink

    ^ Oh I should note. I say this 25 kg lighter after always being a big child and teenager.

  4. Posted May 29, 2012 at 10:56 am | Permalink

    There’s a lot of confusion about what I wrote.

    Or rather: people are projecting other debates into what I wrote.

    The bottom line is that, no matter how complex the internal operation of body weight, it always yields to net calorie balance. In fact, every dietary template ever that has actually worked has, one way or another, imposed or created a net deficit.

    There’s a lot of hocus-pocus advice about diets that tries to either deny or conceal this physical reality. And that really irks me.

    I never said that the relationship between diet and net calorie balance is linear or that the correlation is 1.0.

    Which will be the basis of my next post on the topic, currently in gestation.

  5. TerjeP
    Posted May 29, 2012 at 11:09 am | Permalink

    There’s a lot of hocus-pocus advice about diets that tries to either deny or conceal this physical reality.

    I haven’t encountered any that deny the basic notion of calorie input and calorie burn up. Even the scotch on the rocks diet uses a calorie argument (scotch has calories but melting the ice consumes calories).

  6. Ripples
    Posted May 29, 2012 at 2:29 pm | Permalink

    I tend to be simplistic in my thinking and prefer ideas such as this article where a complex system can be reduced to a simplistic idea.

    I enjoyed this article (though the spinning balls reminded me of Terry Pratchett’s observations in Small Gods)

    For me I have no issue with the premise of the deficient leading to weight loss. The trick is then finding a way to do this that works in the individual circumstances. It can be less in or more out. Some foods in may be harder to get out. There is nothing in the article from my reading that suggests the simple premise is going to be easy.

    I apply something even simpler in the case of smoking. I know that for 20 plus years I smoked and smoked heavy. I blamed everything for me not quitting and tried everything including woo to quit but in the end the solution was quite simple. I managed to stop smoking using a simple premise.

    The trick to not smoking is to not smoke. That’s the most basic you can get. You either smoke or you don’t.

    The issue is managing the transition to non-smoking such as the withdrawal effects, changing habits and all the baggage that comes with quitting the smokes. Yet that for me was the basic lesson in not smoking: if you don’t wish to smoke then don’t. I am still managing the side effects and I have friends who gave up a long time ago and still fancy a smoke. I likely will have to manage the craving for the rest of my life but the base state remains the same; complexity in the personal circumstances but simplicity in the underlying premise.

  7. Kitty
    Posted May 29, 2012 at 2:53 pm | Permalink

    Jacques, you might like to know I heard today that a high level research collaboration looking at the complexity of obesity related diseases is considering framing the overall problem as that of more energy going in than going out. I’m not sure how that will then capture the connections that might have nothing to do with excess energy inputs or insufficient energy outputs (e.g. depression and anxiety appear to have causative links with cardiovascular disease that may be related to an imbalance of the sympathetic and parasympathetic nervous systems – plenty of thin people die of heart attacks) but I can appreciate its use as a simplifying tool as long as it isn’t used dogmatically and connections outside of the model that may arise aren’t dismissed. Though in practice, I don’t think they will be.

    Mel, you are right that it did say high fear campaigns were more persuasive but it goes on to qualify it with: “The results also indicate that fear appeals motivate adaptive danger control actions such as message acceptance and maladaptive fear control actions such as defensive avoidance or reactance. It appears that strong fear appeals and high-efficacy messages produce the greatest behavior change, whereas strong fear appeals with low-efficacy messages produce the greatest levels of defensive responses.” That meta-analysis has its limitations as meta-analyses do, I only used it to illustrate the existence of the defence mechanisms. I don’t think it can say a whole lot about long term effects because time between campaign and effect measurement didn’t feature as a point of analysis as far as I can tell – and relative time of effect measurement is a big problem with properly evaluating these campaigns. That’s not to say all high fear campaigns don’t work, just that many of them don’t work particularly well and can cause more problems – all things to consider before spending a bucket of money rolling them out.

  8. Posted June 2, 2012 at 5:58 pm | Permalink

    This is why people who have lost a great deal of weight are not likely to tell someone — a new employer — about it.

    It is only our thirst for stories (published in magazines that want to sell us things) that sees this kind of mawkish narrative reenactment.

  9. Posted September 23, 2012 at 2:09 pm | Permalink

    Hey! I realize this is sort of off-topic but I needed to
    ask. Does managing a well-established blog like yours require a massive amount work?
    I am completely new to running a blog but I do write in my
    journal on a daily basis. I’d like to start a blog so I can easily share my own experience and thoughts online. Please let me know if you have any kind of recommendations or tips for new aspiring bloggers. Thankyou!

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