Obesity and diet: The first law of thermodynamics doesn’t entirely apply?

Remember Sandy Szwarc of Junkfood Science?

It’s been a long time since we’ve last encountered her. Indeed, it was last year when there developed a debate on whether her posts were suitable for the Skeptics’ Circle. At the time, I was conflicted. In many ways, Ms. Szwarc seemed to be a skeptic–at least, when it came to most topics. However, when it comes to one topic, she is a crank, and that is the topic of the relationship between diet, obesity, and health. It’s not obvious that she is a crank, and it took my reading her blog over several weeks before I came to the inescapable conclusion that all of Ms. Szwarc’s “skepticism” was inevitably in the direction that being obese is not only not unhealthy but is actually at least as healthy as not being obese and that eating fatty foods is not at all unhealthy. To here, virtually any study she looks at that concludes that being obese or eating fatty foods or too many calories predisposes to health problems is a pile of crap while any pile of crap study claiming otherwise is the latest and greatest. She routinely concludes that virtually every warning made by scientists and physicians about diet and obesity as risk factors for cardiovascular disease and other health problems is fearmongering. Worse, after reading her blog long enough, it became clear to me that she has a distressing tendency to use unscientific tactics, such as cherry picking data, attacking scientific consensus, and alleging conspiracies. That Sandy Szwarc is a diet and obesity crank was a conclusion that I came to reluctantly and only after a long time trying to avoid it.

If I had seen this article by her, The first Law of Thermodynamics in real life, I wouldn’t have dawdled over the decision for so long. For, with this particular bit of denialist crankery, Ms. Szwarc has made it completely clear that she is not a skeptic but a crank in a way that is hard to make more crystal clear.

She seems to be implying that the first law of thermodynamics doesn’t entirely apply when it comes to obesity and diet. And you know that when I see something like that, it’s time to apply a little of the ol’ not-so-Respectful Insolence™.

You think I’m kidding? Would that I were! You think I’m exaggerating? Then check out this passage that boils a long post down to its essence:

As is often the case when science is dummied down into soundbytes, it becomes wrong. Such is the case in the distortion of the Law of Thermodynamics which has been simplified into the popular wisdom: “Calories in = calories out.” This simplistic adage has become something “everyone knows” to be true. It’s behind widely held beliefs that managing our weight is simply a matter of balancing calories and exercise. While that’s been used to sell a lot of calorie-reduced diets and calorie-burning exercise programs for weight loss; sadly, it’s also been used to support beliefs that fat people “most certainly must be lying” about their diets and activity levels, because otherwise their failure to lose weight would seem to “defy the Law of Thermodynamics.”

While it might seem inconceivable, this simplified maxim is little more than superstition and urban legend. To realize this fact requires us to first go back to physics class and fill in the missing half of the first Law of Thermodynamics.

The first Law of Thermodynamics, or energy balance, basically states that in a closed system, energy can neither be created nor destroyed, only transformed or transferred.

In a closed system…

The human body is not a closed system! There are countless, wildly varying, and little understood variables that affect the efficiencies of a system and for which we have no control over. Understanding this helps to explain why calories cannot be balanced like a checkbook, and why people never seem to gain or lose as calculated.

See what I mean? Here, she’s setting up an argument to claim that the human body is not a closed system. It’s a case where she is sort of correct on the surface but that she is obviously full of crap becomes obvious with just a little deeper digging. Speaking of digging, though, before I go on to explain, I can’t resist letting Ms. Szwarc dig herself in a bit deeper by quoting a bit more:

Balance in an open system, like the human body, is when all energy going into the system equals all energy leaving the system plus the storage of energy within the system. But energy in any thermodynamic system includes kinetic energy, potential energy, internal energy, and flow energy, as well as heat and work processes.

In other words, in real life, balancing energy includes a lot more than just the calories we eat and the calories we burn according to those exercise charts. The energy parts of the equation include: calories consumed; calories converted to energy and used in involuntary movement; calories used for heat generation and in response to external environmental exposures and temperatures; calories used with inflammatory and infectious processes; calories used in growth, tissue restoration and numerous metabolic processes; calories used in voluntary movement; calories not absorbed in the digestive tract and expelled; calories stored as fat, and fat converted in the liver to glucose; and more. Add to that, to put it simply, each variable affects the others, varies with mass and age, involves complex hormonal and enzyme regulatory influences, and differs in efficiency.

Calories eaten and calories used in voluntary movement are only two small parts of energy balance and are meaningless by themselves, unless all of the other variables are controlled for… which they can never be as they aren’t under our control.

I bet anyone who’s taken freshman physics can spot the misdirection in Ms. Szwarc’s argument. Can you? First, let’s define systems. An isolated system does not exchange energy, work, or matter with their environment. Closed systems, on the other hand, are able to exchange energy in the form of heat and work with the environment, but not matter. An open system can exchange energy and matter with the environment. Somehow, Ms. Szwarc thinks that moving from the thermodynamics of a closed system to that of an open system can be used to justify her argument that somehow all these other sources of energy impact on obesity. She’s wrong.

In an open system, the first law of thermodynamics states: The increase in the internal energy of a system is equal to the amount of energy added to the system by matter flowing in and by heating, minus the amount lost by matter flowing out and in the form of work done by the system. Let’s treat the human body as an open system for a moment. What are the forms of matter and energy that go in and out of the system? Well, going into the system we have food. Food is the only kind of energy the body can utilize on a scale relevant to obesity. After all, we aren’t plants; we can’t use the energy from sunlight to do photosynthesis, nor can we use heat or sunlight to do useful work. All of our usable energy comes from the chemical energy stored in food, the measure of which is the calorie.

The body converts the food it consumes into usable energy in one of two forms:

  1. Chemical energy for immediate use: The “molecular currency” of chemical energy in the body is adenosine triphosphate (ATP). Energy is stored in the phosphate group and released when it is cleaved.
  2. Stored chemical energy: When more energy comes in than can be utilized right away, it is converted to glycogen in the liver. However, the glycogen stores in the liver are rather limited, and after they are topped off the remainder is converted to fat, which is a far more energy-dense chemical form.

No process is completely efficient, of course; so the excess energy is converted into heat. The matter from food goes into:

  1. Production of structural proteins, carbohydrates, etc.
  2. Storage as glycogen or fat
  3. Carbon dioxide and water from respiration
  4. Waste

As far as its being matter, the food that cannot be converted to chemical energy is eliminated as waste, and the matter byproduct of usage of that chemical energy is carbon dioxide and water (leaving aside anaerobic metabolism, of course, the products of which are virtually always eventually used for aerobic metabolism). Because matter and energy can neither be created nor destroyed, the mass and energy from food that enters the body plus the oxygen breathed in during respiration must equal the energy that is used by the body to do work and make heat plus the matter lost through waste and expiration of carbon dioxide plus weight gain due to either storage of energy from food as fat and the use of food components to make structural components. Implying that it doesn’t necessarily have to be so is akin to implying that homeopathy works.

In any case, that doesn’t even seem to be what Ms. Szwarc is even saying; rather the whole bit about the first law of thermodynamics was simply diversion, not to mention a bit of a straw man. Even if it were true that the public so misunderstands physics that its conception of weight loss is in such error, that does not mean that it’s not true that weight loss can’t be achieved through a combination of decreased food intake and increased energy usage in the form of exercise. In addition, she even goes on to mention the second law of thermodynamics. Why? I have no idea. It is largely irrelevant to her argument, even though she is correct that no energy conversion system can ever be 100% efficient in turning heat into work. The best explanation I can come up with is that she is implying that the energy lost due to the second law must mean that energy out will be smaller than energy in, but I’m not even sure of that. I can only conclude her mention of the second law serves the same function that certain hand motions of a magician do: To misdirect the eyes of the audience from what she is really arguing. Instead, she tries to make it sound as though the body’s homeostatic mechanisms for regulating energy and fat don’t follow the first law of thermodynamics:

The human body is a remarkable and incredibly complex and sophisticated system that normally keeps all sorts of things in balance, such as our fluid and electrolyte levels, our body temperature… and, yes, even our fat stores. When fat levels deviate from each body’s natural range, compensatory mechanisms kick in over weeks to return the body to its individual normal state, all without us having to think about it or having much to say about it. Even when eating a range of calories, our body weights stay within a surprisingly narrow range.

Ms. Szwarc then goes on ad nauseam to list examples of research that purport to show that the human body has a “set point” for weight and fat stores that it resists moving away from, either by increasing hunger and decreasing metabolism when food consumption is too low and decreasing hunger and increasing metabolism when food consumption is too high. Even if valid, none of this research goes against the first law of thermodynamics in any way. It postulates that the body either uses more energy or less energy to try to maintain a “set point.” Ms. Szwarc, however, seems to imply that it somehow does by a lot of fancy “energy balancing”:

The energy parts of the equation include: calories consumed; calories converted to energy and used in involuntary movement; calories used for heat generation and in response to external environmental exposures and temperatures; calories used with inflammatory and infectious processes; calories used in growth, tissue restoration and numerous metabolic processes; calories used in voluntary movement; calories not absorbed in the digestive tract and expelled; calories stored as fat, and fat converted in the liver to glucose; and more. Add to that, to put it simply, each variable affects the others, varies with mass and age, involves complex hormonal and enzyme regulatory influences, and differs in efficiency.

Calories eaten and calories used in voluntary movement are only two small parts of energy balance and are meaningless by themselves, unless all of the other variables are controlled for… which they can never be as they aren’t under our control.

Notice the slight of hand here. She’s gone from saying that “calories in” doesn’t necessarly equal “calories out” to saying that calories eaten don’t necessarily equal calories used by voluntary movement. She’s doing it, however, to imply that decreasing one’s food intake or increasing one’s activity level won’t make a difference in losing weight. This is plain silly, as total calories in must equal total calories out. Decreasing food intake and/or increasing physical activity must turn the energy balance to negative. What Ms. Szwarc is really doing is disguising a not entirely unreasonable argument that weight loss is very difficult to achieve because the body’s metabolism adjusts to try to maintain its weight and fat content at a certain set point and wrapping it in a straw man argument about the first law of thermodynamics as applied to an open system Nothing in any of the arguments about metabolic set points violates the first law of thermodynamicss, which she takes to a ridiculous extreme near the end:

The simplistic view that weight management is just a matter of “calories in = calories out” sounds lame now, doesn’t it?

The pop belief that if all of us ate the same moderate diets and did the same intense exercise, we’d all have the same bodies (namely, slender) is something obesity researchers know is a myth. The pop belief that people can simply eat less and exercise more and control their weight defies the first Law of Thermodynamics.

No, it does not

See the straw man argument? Not even the “pop” version of the “calories in = calories out” argument is this simplistic. The “pop” version of the argument is that eating less and exercising more will lead to weight loss, not that everyone can be lean, mean, fighting machines by eating less and exercising more. And decreasing caloric intake can and does lead to weight loss; it’s just that for many people it’s incredibly difficult, perhaps because of the metabolic responses Ms. Szwarc likes to emphasize. None of her blather about open versus closed systems and the first law of thermodynamics changes that. Eating too much food and not exercising increases the internal energy of the open system that is the body by increasing stored energy in the form of fat, while decreasing food intake and increasing work done by the system in the form of exercise decreases the internal energy of the system in the form of decreased fat. It may be incredibly hard for many people to achieve these manipulations because of metabolic and genetic factors, but the physics remains inescapable. Ms. Szwarc’s prestidigitation of language and science doesn’t change that.

Think about it this way: What is the universal end result of every operation for morbid obesity ever devised? It’s a decrease in the number of calories absorbed. Early operations, such as ileal-jejunal bypass operations did it by bypassing a huge length of the small intestine; unfortunately such bypass operations had numerous long term complications, primarily metabolic. (Indeed, I remember having to reverse just such an operation for a patient during my residency because of numerous complications.) More modern operations are designed to decrease the size of the stomach to the point where food intake is severely limited, both physically and physiologically through the feeling of being full after very little food. It’s nothing more than the first law of thermodynamics in action that forces the patient to eat a lot less. Steve Novella also noted that simply keeping a daily diary of food intake can double weight loss.

I’m afraid I just don’t get Sandy. Where she points out that obese people are often demonized and their obesity looked down upon as a moral failing, she does a service. Thanks to a complex interplay of metabolism, genetics, and culture, for many people losing weight and maintaining a healthy weight can be incredibly difficult. In fact, I remain puzzled why she even brought up the first law of thermodynamics, because it changes nothing and only makes her look like more of a crank. In a closed system, energy in must equal energy out, energy meaning the sum of work and heat. In an open system energy and mass in must equal energy and mass out. When it comes to obesity, it’s a distinction that doesn’t mean much, and it’s certainly not a distinction that changes the validity of “calories in = calories out.” Either Ms. Szwarc does not understand the basics of the first law of thermodynamics she had left out the bit about the first law of thermodynamics, she might have even had a reasonable argument to make.

Unfortunately, all the hand-waving and obfuscating in her post designed to make it look as though there’s more to the “calories in = calories out” than just the first law of thermodynamics simply confirms my original opinion of her, namely that she’s a crank but a very skilled and subtle crank. Her writings on obesity had always left me with a feeling that something wasn’t quite right, that her arguments were incredibly one-sided. After I read them again, I had to say either “the stupid, it burns” (because she doesn’t understand the first law) or reluctantly tip my hat to her for being exceedingly clever in constructing a tsunami of confusion by implying that the research suggesting the existence of a metabolic set point in humans somehow “complicates” the the application of the first law sufficiently to invalidate it when it comes to dieting for weight loss.