the perils of calorie counting

I’ve been meaning to write this up for a while, so i can have a reference to send people to rather than rambling incoherently. I’m sure that everyone has been in or overhead a conversation such as this:

Person A: [something about their diet. anything, really]

Person B: *rolls eyes* UGH, *nerd snort*. you’re so STUPID. Losing weight is easy. It’s simple math: eat fewer calories than you burn. I am a left-brained computer/math nerd, so these facts are irrefutable. It’s science!! All your pathetic fad diet attempts are hopeless. It’s impossible for me to be wrong, because I understand the law of thermodynamics.

Of course, anyone that actually knows anything about nutrition would want to punch this person square in the nose, whether they were in the conversation or a passive third-party overhearing it. It’s not simple, actually. The human body is not simple, and “simple math” does not apply. Even from a really gross first-pass analysis, it should be obvious that your body couldn’t possibly be “burning” all the energy you eat, or you wouldn’t have bowel movements. Obviously something still passes through your system, because, shocker, your body can’t use everything it consumes.

First, a quick primer on what calories are (you’d be surprised at how many people don’t really know): “calories” in our nutritional lexicon are really kiloCalories (or sometimes kiloJoules). It’s a measure of the energy contained in food. In traditional science, you’d determine this by using a bomb calorimeter – which is a type of scientific instrument for measuring heat (energy) changes in certain reactions – burning it, for (a crude) example, and measuring the energy (heat) that is released. But obviously the human body is not a bomb calorimeter (tm). It’s a super complex system full of lots of different organs that do lots of different stuff with food depending on what it is, how much we eat of it, and what our bodies have been doing exercise-wise lately. So we can’t realistically use a calorimeter measure, because our body doesn’t burn its food. Instead, the kiloCalorie quantities we see on most foods are determined via estimates of their impact on the body based on their digestibility and other factors. I honestly don’t know what their methodology is, because it’s pretty hard to find. The important part to understand is that it’s just that: an estimate. And it’s an estimate that doesn’t (and couldn’t) take into account the interaction between different food types in the body.

An easy example of this is what happens in your body if you stop eating carbohydrates entirely (as recommended during the “induction” phase of the Atkins diet): your body no longer gets glucose from the carbohydrate. Your body needs glucose, but fortunately your body can produce glucose in the liver by building it with amino acids derived from ingested protein. However, this process is terribly inefficient and keeps your liver so busy making glucose that it doesn’t have the capacity to metabolize fat. Thus, your body literally can’t do anything with the fat it ingests – no matter how much. You can eat 10,000 calories of fat a day, but if your body isn’t consuming carbohydrates as well, it can’t do anything with it.

Conversely, consider what happens if you ate nothing but refined carbohydrates (ignoring for the moment that you would die – your body can make glucose from amino acids via protein, but it can’t manufacture the 20 essential amino acids needed for life from carbohydrates). This is where, as Gary Taubes put it, it gets “unavoidably complicated”, but this video does a pretty good job of explaining it. The long and the short of it is that it results in a something called “hyperinsulinemia” – a condition where your body will be stuck in a bloodsugar/insulin loop wherein you will continue to get fatter while not having any actual energy available to your body.

There are other examples, but these are direct evidence that calories-in/calories-out is just wrong. It’s science, but it’s anything but simple. So, that’s fine, you might say, but aren’t calories still a useful reference? Maybe, but in conclusion, I’d argue not, for the following reasons:

  1. Counting calories leads you to prioritize quantity over quality in such a way that leads you to make poor quality decisions: reaching for the “low calorie” baked Lays instead of something more calorie dense – ignoring that something more calorie dense (an egg, for example) is more balanced nutritionally and will make you feel more full longer.
  2. Most people following a calorie-counting diet paradigm are the same people that have had the low-fat paradigm beaten into their skull and will thus wind up eating something closer to an all-carbohydrate diet (which in its strictest sense would kill you, but as practiced, would just leave you fat, lethargic, and malnourished). Nevermind that carbohydrates are the most calorie-dense form of food, but hey – go look at where most of the calories in your average “low calorie” foods come from. It ain’t protein.
  3. It encourages a hopeless aversion to exercise. If you are focused on calories, they become the reason you exercise. And why bother exercising when that cursed readout on the treadmill indicates that your entire hour of running only got you an extra helping of Lean Cuisine when you’re done? This sort of attitude is wrong on many fronts: first and foremost, exercise helps build muscle, which also raises your basal metabolism (the energy you spend just sitting around being alive) – which is where, unless you’re Michael Phelps, you’re spending most of your energy.. Further, exercise is also good for you in a million other ways that have nothing to do with calories or weight.
  4. It encourages ignorance in general.

Much better is to foster an understanding of what you eat: “oh, I want to bulk up, so I need to eat a shitton of protein, but I know that even though I’ll feel full, I need to eat a ton of it and some carbs, because I don’t want my body burning it for energy”, or “hey, i’m overweight and i have hardly any lean mass – i wanna cut fat, so i am gonna cut carbs out of my diet for a while”, or “hey, i’m about to run a marathon, i need to eat a shitton of carbs so my muscles have plenty of glucose available”. People aren’t stupid, but they’ve been cowed into this ignorant oversimplification of how the body works that isn’t even remotely accurate.