Energy Balance: A Calorie is a Calorie?

In my recent post, Of Nutrition, Commitment, and Progress, I mentioned that I am having CNU count calories due to a tendency to overeat.  It may be thought that I am implicitly stating that caloric surplus is the cause of being overweight, and that caloric deficit is it’s remedy.  This view is appealing to science types, like me, due to the convenient comparison to a “control volume” approximation.  Lets look at the control volume theory of the body and it’s implications.

Here we see the body control volume model.  The control volume is constant in the amount of energy it contains in a state of equilibrium.  So from this model we can see that if you want to reduce the fat (energy stored) in the body control volume, you need to increase Energy Out and/or decrease Energy In.  This model is how the “eat less move more” dogma has come about.  It turns out, to no shock of those who have struggled with losing weight, this model is flawed.

The control volume model is mathematically equivalent to a lake with a dam.  On any given day some amount of water will come in and some will leave.  For our body control volume model, the level of water in the lake is equivalent to the body fat level.  When it rains or snow melts water enters the lake.  When the dam opens or when water evaporates, water leaves the lake.  I am assuming the water has no other way out.  These are good corollaries for movement and heat in the body control volume model.  If it never rained again (you never ate) the water level in the lake would drop to zero due to evaporation over time or water through the dam.  Likewise if the dam never opened and we could some how stop evaporation and it rained a lot the level in the lake would have to rise.

Ask yourself this.  If you are at the controls of the dam, and it hasn’t rained in months is it going to effect how much water you let through the dam?  What if it’s been pouring every day for weeks?  You probably have goals for water levels both in the lake and downstream so you are not going to just let water out at a constant rate no matter what’s happening with the flow of water into your lake.  Your body is the same way, but far more complicated.

Let’s first look at a model that represents more complex ins and outs.  Using the lake analogy again, lets consider the operator of a lake that has canals that feed it and a dam like before.  In this way the operator may control the level of his lake by both adjusting the water out of the dam, but also affecting the water in by controlling the canal flow.  With this control, our operator will make decisions for the flow in or out based on the flow out or in and the level of the lake.  The human body works in the same way.

If you go workout regularly, increase your Energy Out, you’ll find that you are hungrier and desire to eat more.  Likewise if you’ve seen what happens when a 3 year old who get’s a big batch of candy, you’ve see that an increase of Energy In can lead to and increase in Energy Out.  The body creates a hormone called Leptin.  This hormone is released in proportion to the amount of body fat you have.  It acts like a fuel gage of sorts and helps to regulate hunger.    To drive home it’s role in fat regulation; the hormone was discovered in mice that had a gene mutation that resulted in a lack of Leptin receptors.  With out these receptors, the mice were constantly hungry and became obese.  So the inability to sense Leptin, called “Leptin Resistance,” can lead to overeating and obesity.  Fructose has been implicated in causing Leptin resistance.  This starts the explanation of why calories in and calories out is an overly simplistic model, and fails to help stem the tide of obesity world wide.

Let’s consider a third even more complex model for the body.  This is where the lake model falls apart, and why the original control volume theory is such a poor model.  The model I’ve shown at left is EXTREMELY crude and not a full representation of internal fat regulation, but is intended to make a point.  In a lake, water cannot hold itself back from the spillways of the dam.  If the dam opens, the water cannot resist it’s flow out.  Body fat CAN resist it’s flow out of the body, or better said, it’s flow can be resisted.  Insulin is a hormone that the body releases to keep blood sugar at healthy levels.  Too high and you’ll die, too low and you’ll die.

When you eat a carbohydrate rich meal, think that big plate of pasta, you often feel very lethargic and have a big crash some time shortly after.  This is a result of the body releasing insulin to clear the excess blood sugar from the blood.  The problem with those carb rich meals is they cause the body to over release insulin and once the blood sugar is cleared, the left over insulin goes on reducing your blood sugar even more eventually leading to low blood sugar leaving you feeling drowsy.  So where does that sugar go?  Insulin binds to muscle and fat tissue in the body telling them open up and take in the sugar from the blood.  This, over time, can lead to increased fat accumulation.  In people with hyperinsulinemia, chronically elevated insulin levels, the body can pull needed calories from the blood and store them as fat instead of making them available for Energy Out.  This can result in chronic lethargy, making it very difficult to heed the “move more” advice.

As with Leptin resistance, Insulin resistance can occur.  Insulin resistance, unchecked, will lead to Type 2 diabetes.  This is part of my rationale for believing that diets high in carbohydrates are intrinsically bad and a cause of obesity.  A FAR more detailed discussion can be found in Good Calories, Bad Calories.  It is a read I cannot recommend more highly.

I hope I’ve made a reasonably clear and concise argument against the idea that a calorie is a calorie, and that the energy balance equation is far from a complete model of body fat regulation.  With that said, you can eat too much.  Even without carbs, you can just plain eat too much.  If you do it will result in weight gain.  With this said, the energy balance equation is part of reality, not it’s whole.