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Do you want to gain lean mass, lose body fat or maintain your current body composition? If you do, you might end up seeking out a specific nutrition or movement plan to aid your efforts. And as a consequence of that, you might also have to figure out your caloric baseline. Your body has a dynamic need for certain amounts of macro- and micro-nutrients, and the starting point for calculating that dynamic need usually involves the calorie. But what is a calorie, anyway?

A small 'c' calorie is a measure of the energy contained within a foodstuff. More specifically, it is the amount of energy required to heat one gram of water by one degree Celsius. Scientifically, that is fact. But it's also rather abstract. We're more familiar with calories in relation to macronutrients and food.


The number of calories contained in a gram of a specific macronutrient was determined over a century ago.

- A gram of protein contains four calories.

- A gram of carbohydrate contains four calories.

- A gram of fat contains nine calories.

These values were adjusted to account for the calories not absorbed during consumption, and they represent averages for each of the macronutrients.


Unfortunately, the food we eat is not so easily separated into protein, carbohydrate and fat. Most of the food we eat is a mixture of all three. Further, as hinted at above, the calories in a food we consume are not necessarily the same as the calories we absorb. Recent studies have found that there are significant variations in the absorption rates of certain foods. For example, nuts and seeds have much lower rates of absorption compared to simples starches, and fiber-rich foods have different absorption rates, depending on the type of fiber.

It gets more complicated. The makeup of the bacteria in one individual's gut varies compared to another. And guess what? Gut bacteria health affects food absorption as well, which means two people with the different gut bacteria absorb the same food differently. Our genetic makeup also affects absorption--some are better equipped to digest certain foods than others, for example. The quality of our sleep can affect digestion and absorption of macro- and micronutrients, as can disruption to our circadian rhythms, our activity on a macro or micro level, our hormones, and the timing of food consumption.


Two people consuming two items of food with identical caloric values will absorb the food's nutrient differently. That is because we are all different within and we all metabolize calories differently. But external factors also affect nutrient and calorie absorption.

Chopping, cooking and processing food alters the total percentage of the nutrients absorbed. Shredded raw carrot yields a different absorption pattern to a sliced and roasted carrot; a fruit smoothie gives more calories quicker than the same fruit eaten whole; the calories in certain freshly cooked foods (like pasta and bread) are more readily absorbed than the calories in the same food that’s been left to cool and then reheated.

Plus, there is the issue of recording calories. A large proportion of the foods we consume come in a package which displays nutritional information. But these numbers don't tell the full story: American government regulations allow food companies to use different methods to estimate calories and the FDA allows inaccuracies of up to 20%. Similar (and sometimes higher) inaccuracies have been reported in nutrition information provided by restaurants.

Finally, it's been shown that we are somewhat biased when tracking our food intake. Do you know how much food you ate yesterday, or last week? It's probably more than you think. Say you do journal or log your dietary habits. How accurate are your records? Do you weigh every morsel, calculate every milliliter of oil that you put in the pan? And what database are you using--because often two databases will offer different nutrient profiles for similar foods.


You are probably wondering why I am telling you all this. It's not because I want to make quantitative approaches to nutrition seem pointless. They're not. It's more because I believe that greater understanding leads to better, more informed choices. Yes, I am exposing the difficulties and inaccuracies of the calorie as a tool, as well revealing the complexity of our bodies. But only in the hope of prompting you to ask more questions about the food you eat and the effects it has.

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