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Post by reddarin on Jul 9, 2013 18:34:30 GMT -6
SAD acolytes use the ol' Laws of Thermodynamics bat to smack us around with all the time. Well, the truth is that the human metabolism is not a simple closed system. It is an open complex system with an unknown number of variables that all interact with each other. So it isn't and never has been as simple as Calories In Calories Out. Here is a very gruff post on the topic I found on the internet. I've edited the obscenity but otherwise it is the original text. The post he is replying to is an image on the site I got this from so I've included that too:  I’m a physicist, and you’re ******* wrong. Sorry. The metabolism is a complex system with many variables. Efficiency of the system varies not only from person to person, but throughout someone’s life. That’s the second law of thermodynamics, the one that governs chemical reactions. You’re hung up on the first law, which is just a conservation law (bookkeeping).
Humans aren’t lawnmowers. God I hate educating you trolls. Spend three seconds thinking about this instead of copying a paragraph from your thermo 101 book. Do you really think a teenager has the same metabolic efficiency and rate as a 70 year-old man? A pregnant person as a non-pregnant person? Someone with a healing wound as someone whose body is enduring the depths of famine (or is dieting)?
The metabolism isn’t perfectly understood, definitely by people like you, and even by researchers. There are theories out there about a bodyweight setpoint around which a body fluctuates, but towards which a body tends, mostly programmed by genetics and partially by history and environment. This means the metabolism resists weight loss below a certain point, and it also resists weight GAIN above a certain point.
Also, fat people haven’t been shown to, in general, eat any differently than thinner people. Which means they’re not consuming a giant amount of food to make their bodies bigger. And 95% of diets fail long-term, which means your little “it’s easy, eat less move more!” prescription doesn’t work, which, if you’re a scientist (please I hope you’re NOT), points to some kind of fatal flaw in your theory.
Here’s a list of resources compiled by Michelle at the Fat Nutritionist. Which you probably won’t read, if you’re ignorant enough not to understand how the laws of thermodynamics apply to chemical reactions and human metabolic systems. But my readers are sharp and reflective folks (not literally, freshman!), so they might appreciate it.
(made rebloggable by request) |
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Post by reddarin on Jul 9, 2013 18:35:33 GMT -6
Another explanation of why bumper sticker thermodynamics does not describe the human metabolism. junkfoodscience.blogspot.com/2008/10/first-law-of-thermodynamics-in-real.html
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 eaten 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 parts 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.
The human body is not a machine. There are countless, wildly varying, variables (external and internal) involved and 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 precisely as calculated.
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 matter 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, as our metabolism… which they can never be as they aren’t under our control.
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Joined: January 1970
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Post by Deleted on Jul 10, 2013 18:18:05 GMT -6
Those are excellent posts.  I'd forgotten about the junkfoodscience blog, too bad it isn't being updated anymore. |
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I'd forgotten about the junkfoodscience blog, too bad it isn't being updated anymore.