How Much Fuel Do We Need?


How Much Fuel Do We Need?


Last week we broke down food as a fuel source. We talked about the different kinds of fuel our body needs (macronutrients) as well as the quality of that fuel (micronutrients). Let’s do a quick recap – our body needs 3 main sources of energy to survive: Carbohydrates, Fats and Proteins. These are also referred to as Macronutrients (or Macros for short) and pretty much all food falls into these 3 categories in one way or another. From there we can determine food quality as better or worse based on the amount of micronutrients it has. We didn’t get into micronutrients very much last week; we just said that generally the more micronutrients a food has the better it is for us. If a food has very little micronutrients, chances are it is processed, aka junk food.

So now that we know the different kinds and different qualities of fuel, the question becomes: how much fuel do we actually need? On the surface we have a very simple answer to that: Eat at levels that support activity but not excess body fat. This means that your intake level should be enough to keep you energized through your day, through your workouts, etc., but not so much that you are putting on unhealthy weight. Simple enough, right? Or maybe just a little complicated? Well hey, that’s what I’m here for! Let’s break it down.

Using Energy

There are three primary ways our bodies use the calories we consume: Resting Metabolic Rate, Thermic Effect of Food, and the Thermic Effect of Physical Activity. These three things make up our total energy expenditure, which is essentially the total number of calories our body uses on a daily basis. In order to figure out how many calories we need we just need to figure out these three components. Like I said, super easy!



Resting Metabolic Rate

Your resting metabolic rate is the amount of calories that your body uses for its every day normal functions – pumping blood, breathing, going to the bathroom, etc. All of the stuff that happens inside of our body requires calories. This number is greatly affected by your gender, age, height and weight; obviously a 200lb man requires more energy to pump blood throughout his body than does a 120lb female.

Thermic Effect of Food

The Thermic Effect of Food has to do with the energy it takes for the body to break down and distribute nutrients from food that you eat. For example, say you eat an apple that has 100 calories in it. It takes a small percentage of those calories to digest the apple and then distribute the nutrients to all of the cells of the body. Generally, the more nutrients a food has the more work it takes to digest and distribute, so the greater the Thermic Effect of Food. Again, this is a small percentage of calories, but significant enough that we can’t ignore it.

Thermic Effect of Activity

The third and most significant determinant of your caloric expenditure is the Thermic Effect of Activity – how many calories you burn on a daily basis due to your activity level. This one is going to have a wide range based on your lifestyle. Do you have a physically demanding occupation or work in an office? Do you chase your young children around or watch tv all night? Do you exercise at all or no? Obviously the more active you are, the higher your Thermic Effect of Activity will be.

Calculating your Expenditure

Now that we know how our bodies use energy, it’s time to figure out how much we actually need! Step one is to calculate your metabolic rate. The best and most accurate way to do this would be to find a nutritionist and pay a decent amount of money for a calorimeter test to be done on your body. However, that isn’t the most practical, or completely necessary. There are tons of calculators online or on fitness apps that you can use for free. They aren’t 100% accurate, but close enough. All you need is your sex, your age, your height and your weight, and then put this all into the calculator. Step 2 is to determine your activity level based on occupation and number of workouts you do in an average week. If you work in an office, don’t consider any additional activity. If you work construction or are on your feet all day, you can probably count it as an extra workout or two per week.

Once you have determined your activity level, you can enter it into the calculation with your metabolic rate. The result will be your estimated caloric expenditure, or more simply the total number of calories you burn on a daily basis. Keep in mind this is only an estimate. What we really need to do now is test this number to see how accurate it is. If you go a week or two eating this number of calories you should have a pretty good idea of how your body is handling it – do you feel hungry, full or satisfied? Do you see any differences in the mirror? Are your workouts being affected, either positively or negatively? Once you have this data you can adjust your calorie number to accomplish whatever your goal is – want to lose weight? Drop your intake by 150-200 calories per day. Want to add muscle? Increase your intake by 150-200 calories.

Your homework today is just to figure out your estimated calorie intake level. It might surprise you. Modern media has painted an evil portrait of calories, saying less is better. Well now we know that the right amount is better. However we can still get a little more nuanced with our nutrition. Part three is going to be all about how we can modify your diet for your particular goals, your experience level, and your preferences. Diets aren’t cookie cutter, and since nutrition is something we have to worry about every single day, multiple times per day, it’s important that we make our diets work for us.