[fgummett]

Nature Clinical Practice Endocrinology & Metabolism | Childhood obesity: behavioral aberration or biochemical drive? Reinterpreting the First Law of Thermodynamics | Article

Summary

Childhood obesity has become epidemic over the past 30 years. The First Law of Thermodynamics is routinely interpreted to imply that weight gain is secondary to increased caloric intake and/or decreased energy expenditure, two behaviors that have been documented during this interval; nonetheless, lifestyle interventions are notoriously ineffective at promoting weight loss. Obesity is characterized by hyperinsulinemia. Although hyperinsulinemia is usually thought to be secondary to obesity, it can instead be primary, due to autonomic dysfunction. Obesity is also a state of leptin resistance, in which defective leptin signal transduction promotes excess energy intake, to maintain normal energy expenditure. Insulin and leptin share a common central signaling pathway, and it seems that insulin functions as an endogenous leptin antagonist. Suppressing insulin ameliorates leptin resistance, with ensuing reduction of caloric intake, increased spontaneous activity, and improved quality of life. Hyperinsulinemia also interferes with dopamine clearance in the ventral tegmental area and nucleus accumbens, promoting increased food reward. Accordingly, the First Law of Thermodynamics can be reinterpreted, such that the behaviors of increased caloric intake and decreased energy expenditure are secondary to obligate weight gain. This weight gain is driven by the hyperinsulinemic state, through three mechanisms: energy partitioning into adipose tissue; interference with leptin signal transduction; and interference with extinction of the hedonic response to food.

In other words...

The commonly accepted assumption (and it is only an assumption) is that we store excess Fat because we eat too much and/or exercise too little.

This review proposes another way to interpret the exact same observations by turning the assumed cause and effect around... in this scenario we eat more and/or exercise less because the body (under biochemical control) is storing Fat. Or... if the body were not storing Fat, then we would not be overeating or looking for ways to conserve energy

Think of it this way... when a teenager goes through a growth spurt they eat everything in sight (ask any parent)... but in this case we don't suggest that they are "growing because they are eating" but rather that "they are eating because they are growing".

The big difference now becomes that instead of looking for ways to change the "behaviours" of gluttony and sloth -- and we all know how successful that has been -- we can instead ask the question "what controls the biochemistry of Fat storage?" In the expectation that by curtailing the Fat storage you free the person from the need/drive to overeat and promote spontaneous physical activity.

The idea of switching from being in a "Fat storage" mode to a "Fat burning" one, fits my personal experience... I can especially relate to the "normalised" hunger and spontaneous physical activity... and trust me I have tried many different versions of the other model.

 

[fgummett]

Hunger, just like thirst, the need to breathe, empty the bladder, evacuate the bowels and several other things are biological needs or drives that many animals including humans have.

Like many other animals -- but particularly because we are fine, upstanding, civilized humans -- we also have a level of conscious control over many of these drives (fortunately we don't need to be awake to breathe). So while we may hold our breath for a while (and deep divers can train to do this for extended periods), or even hold back our thirst to the point where we become dehydrated... at some stage we either have to satisfy these needs or suffer the consequences -- up to and including death.

Ahh but "surely hunger is mainly a conscious drive?" you say ... "I chose what and when I want to eat based on smell, taste, look etc..." -- OK, consider that it is near supper time, you haven't eaten for several hours so you visit a gourmet restaurant where the Chef's special captures your nose, eyes and taste-buds. You eat and enjoy the meal... you are satisfied... but now the pretty waitress brings you a second serving of the same meal... does it have the same effect on your taste-buds? Of course not! Because your physical need to eat (AKA hunger) has already been satisfied.

Hunger is a physical/biochemical drive. Yes you can push it off for a while but if you are physically hungry it does not go away until lit is satisfied. In order to lose excess Fat mass we are not talking about just one meal... or one day... we are talking about weeks and months and years. I heard someone suggest it is like holding your breath until you pass out, then when you come to, you do it all over again... over and over and over... sounds like fun, but I bet someone with a whole whack of will power could do it!

It is important to recognise that eating is NOT just about intake of energy/calories... we are providing the body with ALL the essential nutrients BUT until we have provided all those nutrients we remain unsatisfied -- hungry.

Yes! in order for excess Fat mass to be stored, at some point, overeating must occur -- that is the 1st Law of thermodynamics! but it says nothing about which is cause and which is effect.

If we eat because we are hungry and some of us continue to eat because we are STILL hungry, perhaps the question is as simple as "why are we still hungry?"... if we can solve the hunger then we don't have to solve the overeating.

 

[fgummett]

Here is a good read explaining why the simple idea of "calories in minus calories out" is incorrectly applied to humans...

Junkfood Science: The first Law of Thermodynamics in real life

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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 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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