Regular people like you and me, as well as "experts", professionals, and other pundits, invoke this analogy all the time. I have been known to say it myself. "Calories in / calories out"... To lose calories, you must either "eat less or burn more". End of story! Being an engineer, I'm familiar with the laws of thermodynamics. The first law of thermodyanmics is the law of "conservation of energy". This means that any excess food you eat cannot vanish into thin air, therefore, it must be stored as fat. And if you don't eat enough calories, your body cannot create them out of thin air, and you will lose fat. But... is that really the "end of the story"?
Let's say we subscribe to the "calories in / calories out / end of story" theory. Let's consider another analogy. Down the road from me is Michigan Stadium, home of the Michigan Wolverines, where on Saturdays in the fall there are typically about 115,000 people shoehorned into the bleachers to watch a football game. Down the road a few miles to the east, is Rynearson Stadium, home of the Eastern Michigan University Eagles. This stadium is also hosting a game, but the spectators are few and there are plenty of extra seats. You might ask, why are there so many people in Michigan Stadium? Simple... it's just a matter of people in / people out! More people entered the stadium than exited. True enough, but why did they enter and not leave? And why didn't the same thing happen at Eastern Michigan University? Clearly, "people in / people out" does not answer all the questions. Just like calories in / calories out does not fully explain weight control.
One milestone in this discussion was the publication of "Good Calories, Bad Calories" by Gary Taubes in 2007. Here is Taubes' explanation in a nutshell: Our food-burning, energy-producing, fat-storing metabolism is complex. Foods affect our bodies in different ways and are processed through different metabolic pathways. Not only that, but the foods we eat can directly affect the hormones that regulate when and how much we eat, as well as what our body does with those foods. The most important of these hormones being insulin. How the body processes its food intake is strongly dependent on insulin.
Consider another analogy - the automobile and its fuel tank. Imagine that there is a tiny valve somewhere in the car that directs a cupful of gas of each tank to a "reserve tank"? This reserve tank is available to be used by the car, but not easily. The tiny valve sometimes opens to let gas into the reserve tank, but does not often open to let gas out of the reserve tank. And this reserve tank is separate the main tank. So when the main tank is empty, the fuel gauge says "fill me", even though there is plenty of gas on board in the reserve tank. And so the reserve tank gets larger and larger, filling up the trunk, the roof top carrier, the u-Haul trailer, etc.
There is such a reserve tank on the human body - the fat cells. And, it turns out there is exactly such a "valve" on the human body... over the course of time, an abundance of insulin directs the body to store an inordinate amount of reserve energy in fat cells. And the insulin makes it difficult for the body to access this fat, so we feel hungry. Instead of using the fat, we do what comes naturally when hungry, we eat!
What causes excess insulin? Long-term consumption of carbohydrates! So we have a vicious cycle. Eating carbohydrates increases blood sugar, causing the body to produce insulin, which directs the body to store excess energy as fat, and makes it hard to burn the stored fat. This makes us hungry. What do we do? Eat more carbohydrates. And the cycle is repeated. That is explained briefly in this video segment from the film "Fat Head" Tom Naughton:
By the way, Fat Head is an excellent documentary and tells the whole story. If you have the time, I recommend you watch the whole thing! It's free on Hulu.
So, in conclusion... A Calorie is a Calorie... Yes? or No? Actually, both yes and no. On one hand, yes, if you eat more calories than you expend, the excess calories will be stored as fat. There is no getting around it. If you want to lose body fat, you must eat less than you expend.
On the other hand, they type of food you eat does affect what your body does with its calories. If you eat a high carbohydrate diet over a long period of time, your body (thanks to lots of insulin) will develop the tendency to store lots of fat, whether it needs to or not, and lock that fat up, making it difficult to burn.
So what does this mean? Can you eat all the bacon and steak you want and still lose body fat? No. On the other hand, can you eat a high carbohydrate diet, large servings of pasta and "healthy whole grains", as instructed by the USDA "Food Pyramid"... (now superseded by "My Plate") and expect to lose body fat? No! And the evidence suggests that you will feel hungrier and eat more when eating a high-carbohydrate diet.
Does it work? In my case, I would have to say yes. In the past it seems like my weight would drift up over the years, as if there were a "set-point" it was aiming for. If I was not watching carefully, "counting calories" my weight would constantly creep up. I was able to reduce my weight by about 25 pounds over the course of a several years by "counting calories". This was from 1995 to about 2003. Then I quit paying attention, and all 25 pounds came back over the next three years. Back up to the "set point". So I worked at it again and lost the weight again. For the last three years I have been able to maintain the reduced weight, about 25 pounds below the maximum, without "counting calories" or consciously eating less. I just cut out the sugar, sweets, and the a great deal of the carbohydrates, while increasing fats and proteins. (It is important to eat the "right" fats. More on that in a future post.)
So if you are following the USDA's advice, and eating lots of whole wheat pasta and other "healthy whole grains" and lots of "low fat" foods, and yet the pounds keep creeping up, perhaps you need to cut back on the carbohydrates and increase your fat and protein intake. But wait! Isn't the high-carb, low-fat diet also known as the "heart-healthy" diet? Won't we "plug up our arteries" eating "artery-clogging saturated fat"? Shouldn't we be eating lots of "healthy whole grains"? Surprisingly, the answer is "no"! More on that in a future post!
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