In a previous post, I talked about my own tests with ketogenic diets, along with my use of borderline OCD food and exercise tracking combined with a BodyMedia FIT to test the theory that calories matter. In short, the answer is yes, which is obvious if you really think about it, and even more obvious if you follow the research. So, in this post, I’ll explain why they matter.
First, from a basic thermodynamics standpoint, they matter because they have to. It really is that simple, so if nothing else I’m about to say makes sense, just remember that.
The first law of thermodynamics states that in an isolated system, the amount of energy in the system must remain constant. What this ultimately means is that you can neither create nor destroy energy. Energy cannot be generated, it must come from something. So, if you expend energy, it must come from something; either something you ingest, or something you already have stored (tissue, like fat or muscle) because you ingested energy in the past.
Calories are a measure of energy. So when you are counting calories, you are simply tracking the energy flow into and out of an isolated system (you). If the isolated system (you) increases in mass (weight), this must be because the energy entering the system was greater than the energy that left it. There is no other explanation that does not violate the first law of thermodynamics. Similarly, in order to reduce the mass of the isolated system (short of physically removing parts ala amputation), you must intake less energy than you expend. Period. There are no other answers, this is the winner.
This means that all of the hogwash about calories not mattering is just that: hogwash. However, this doesn’t really debunk the other argument that ketogenic diet proponents (in particular) fling about a lot: That due to differences in the way the body processes protein, fat, and carbohydrate, you get less energy out of fat and protein than carbohydrate. So, let’s tackle that part.
First, let’s examine raw energy value for each macronutrient. Of the three, fat is has the highest energy content, with 9 calories per gram. This is followed by protein and carbohydrate, which have an identical energy content of 4 calories per gram. So, right away, you can see that empirically, carbohydrate does not contain more energy than fat or protein. However, that doesn’t mean that the body necessarily processes each nutrient at the same level of efficiency, so let’s look at that.
Efficiency-wise, the body processes protein with about 80-95% efficiency, depending upon the protein source. Carbohydrate is processed with an 80+% efficiency, but that assumes that fiber (which is indigestible) is counted in the calorie count. So, let’s assume just for the sake of argument that there is no fiber in our carbohydrate and we process it with 100% efficiency. Fat, finally, is processed with 97% efficiency.
So, the “metabolic advantage” of a ketogenic diet is at most 20%, and only then for the portion that consists of proteins from sub-optimal sources. On most ketogenic diets (and especially Atkins), you will see a very high fat content with a moderate to high protein content. On a 2500 calorie ketogenic diet, you will likely see a an average protein intake of 150 grams (600 calories), a carbohydrate intake of around 20 grams (80 calories), and the remainder (1820 calories) made up with fat. Assuming that all of the protein is of the poorly digesting variety (600 x 80% = 480 net calories absorbed), the total caloric intake is 2325 calories per day. This makes the “metabolic advantage” of the ketogenic diet a whopping 175 calories per day at most. At that deficit (assuming you never, ever cheat), you will lose roughly 1 pound every 3 weeks, or roughly 17 pounds per year. Unfortunately, since keto diets almost never suggest that you count calories and modify your eating habits, what actually happens is that you just eat enough extra protein and fat to overcome this ‘advantage’ and maintain the same weight. Regardless, the “metabolic advantage” of a keto diet is, at best, very slim. And in the end, if you do lose weight, it still boiled down to the same thing: You reduced calories.
However, some of you may have read some research or some literature that states that the body cannot convert carbohydrate or protein into fat, and therefore, we can eat all that we want of one or the other and not ever gain weight (the speculation here is that we will just excrete the excess calories). Interestingly, the first part of this is largely true, but unfortunately, that doesn’t mean the second part is. Let me explain.
First, let’s get fat out of the way: fat is fat. Your body’s first reaction to fat is really very simple: it wants to store it. Burning it requires a little bit of energy (the 3% efficiency thing from above), but storing it is basically free, so that’s what it wants to do. Keep this in mind as we discuss protein and carbohydrate.
Carbohydrate is burned for energy. Period. Under most circumstances, the body will not convert carbohydrate into fat. The only time the body breaks this rule is when you are at a caloric surplus and the caloric surplus is greater than the incoming calories of fat. Under these conditions, the body will initiate lipogenesis and convert carbohydrate into fat. Otherwise, carbohydrate is your body’s primary and preferred energy source.
Protein will basically never be converted into fat. The body can, mind you, it’s just that, under any real circumstance that will ever occur, it will never happen. Basically, the only way the body will convert protein to fat is if you only eat a diet of pure protein at a caloric surplus (almost impossible). Your body’s first reaction to protein is to use what it needs to support bodily functions (generation and repair of new tissue, for example) and burn the rest for energy.
So, based on that discussion, fats are obviously bad, as the body tries to store those immediately. And carbohydrate is bad if you are at an energy (calorie) surplus, as the body will either fail to burn some of the fat you ate and use carbs instead (storing the fat), or if you ate very little fat, will initiate lipogenesis and convert the carbs to fat for storage.
But what about protein? It looks like, perhaps, you could eat a LOT of protein and never get fat. Not really. Let’s say you only ate steaks. 24/7 you eat a ton of steaks, so you should be getting no carbs and a ton of protein, right? Let’s see.
Here’s the breakdown of a single ribeye steak (10.5 oz), trimmed to 0” of fat, according to the USDA:
Protein: 63 grams
Carbohydrate: 0 grams
Fat: 40 grams
Calories: 625
So, let’s say you eat a caloric surplus of 500 calories per day for a total of 2500 calories, just of steak. You would need to eat a total of four of these steaks every day (42 oz). You would have consumed 160 grams of fat for 1440 calories and 252 grams of protein for 1060 calories. So your 500 calorie surplus is easily met by the fat content of the steak, and will be stored as fat, no lipogenesis necessary.
But what if you go even more extreme, finding a nearly pure source of protein? Well, say you were to consume nothing but protein powder, which is almost entirely protein. As an aside, this is something I would not suggest under any circumstances. At best, you will end up severely malnourished due to lack of micronutrients and at worst, severely sick due to heavy metal poisoning (as many protein powders have high quantities of heavy metals in them from processing). Anyway, Optimal Nutrition 100% Gold Standard Whey Protein has the following nutrients per scoop:
– Protein: 24 grams
– Carbohydrate: 3 grams
– Fat: 1.5 grams
– Calories: 120
So, a 2500 calorie diet consisting solely of protein powder would consist of 21 scoops of this stuff. After that, you would have consumed 31.5 grams of fat for 284 calories, 63 grams of carbohydrate for 252 calories, and 504 grams of protein for 2016 calories. In this case, you still have enough calories in fat and carbohydrate to cover your surplus, and your body never needs to convert protein to fat to still store fat and make you gain weight.
And even if you go farther and find a more pure protein source (like light tuna), the best you can hope for is that your body will finally break down and convert protein to fat for storage. That’s it. All that hard work just to prove that, yes, in completely unrealistic conditions, the body can and will convert protein to fat.
Ultimately, there are no magic bullets. To lose weight, you must consume less calories than you expend. Anything that claims you do not is, at best, smoke and mirrors and at worst, ineffective and possibly dangerous.
For those of you more scientifically inclined that want to read a deeper treatise on this subject, I’d like to point you to several more articles with a significantly more in-depth analysis:
Excess Protein and Fat Storage – Q&A
Is a calorie a calorie?
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