I originally wrote this article for my newsletter and it has since been posted on my site. It seems very fitting for here given the questions we seem time and time again. If you have any questions about the content of the article, feel free to ask here in this thread.
In the last edition of Nutrition Corner we discussed the importance of defining and understanding the difference between calories and macronutrients. If you haven’t read that article yet, I highly suggest you take the time to do so before delving into this installment.
After reading the above-referenced article, some messaged us asking, “The article is great, but how do I go about determining how many calories I personally need?”
Before answering, I’d like to remind you that counting calories isn’t for everyone. That’s not to say some aren’t bound by the laws of energy. It’s just that some find it tedious and obsessive to a degree that detracts from real progress. The only way to find out if you’re a member of this camp is to give it a try. As mentioned in the last article, even if you determine counting calories isn’t for you, it will still provide an invaluable insight as to how quickly calories can add up as well as what serving sizes really look like.
With that said, let’s delve into how one goes about calculating caloric needs.
To summarize from the last edition, caloric expenditure is determined by BMR, TEF, TEA and NEAT which are basal metabolic rate, thermic effect of feeding, thermic effect of activity and non-exercise activity thermogenesis respectively. As these factors rise and fall, so does your caloric expenditure.
Once we determine what we’re approximately expending, we’re able to tailor our intake to match our goal of either gaining, losing or maintaining weight—eat more than we expend to gain, less than we expend to lose and the same as we expend to maintain.
So how do we determine total expenditure?
We could find a lab with a metabolic chamber where they use calorimetry to measure the heat our bodies produce or the levels of gas exchange (oxygen consumption, carbon dioxide production, etc). You’ll have to live in a small room for a day or two to get an accurate reading. If you’re normal, this method is about as practical as climbing Everest as your form of weekly cardio.
I’m sure some of you have watched the Biggest Loser television show. On there you may have noticed contestants wearing what’s called a Bodybugg. This nifty device estimates caloric expenditure using various factors including movement, heat, electrical conductivity, etc. So you could purchase a similar device to measure energy expenditure.
You could plug some of your statistics into an equation such as the Harris Benedict formula which will spit out an estimation of your basal metabolic rate. These vary based on sex and look like:
Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )
Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in year )
Once you complete the math, you then multiply your answer by an “activity factor” to get your estimated total energy expenditure per day. These factors look like this.
Formulas like the aforementioned are the basis for a lot of the calorie calculators that you see on the Internet. These are very simple to use typically asking you to plug in your age, sex, height and weight and with the click of a button you’ll have an estimated caloric expenditure.
This isn’t a complete list of methods of calculating caloric expenditure but it does contain the most popular techniques. Frankly, I don’t use any of them—well I should say I almost never use any of them.
Here’s why.
Caloric needs are very individual and variable.
By individual, I mean two given people with similar body compositions and lifestyles may have varying degrees of variability in energy expenditure due to genetic factors affecting metabolism. It should be noted that this variability isn’t as great as many make it out to be—if you’re of the type that believes you have a “slow metabolism” thus making fat loss impossible without starving yourself, you better think again (outside the realms of clinical issues). But variability does exist and this is something that the above methods are not going to pick up (shy of the metabolic chamber).
By variable I mean caloric expenditure will change from day to day and month to month. For instance, our lifestyles will dictate how much energy we expend. Think about how some are more active during the week than the weekends or think of an off-season compared to in-season schedule for an athlete. Caloric expenditure will change based on your energetic state (or diet if you will)—meaning if you’re continuously eating less energy than your body needs, your body is going to adapt by slowing down your metabolism over time.
The simple act of losing weight will reduce your caloric expenditure. You’ll have less tissue to support, less mass to move around, etc.
Beyond the fact that caloric needs are individual and variable, the accuracy of these rudimentary tools (sans calorimetry) tends to diminish as you approach the ends of the spectrum of leanness or obesity.
Hopefully you’re starting to see a) caloric expenditure is not a rigid, consistent thing and b) that unless you’re spending some time in a metabolic chamber the tools you use to estimate caloric expenditure are rudimentary in nature and at best give you an approximation.
Knowing this, it is beyond me why so many get hung up on calculating their total energy expenditure. Invariably I’ll see people at wits end ready to pull their hair out fretting over the option to eat 1850 calories or 1950 calories because they used two online calculators and each spit out a different determination.
They’re missing the forest for the trees.
I put an enormous premium on simplicity. I don’t see much a point in muddying the waters until I reach a point that requires some mud-stirring. Until that point arises, I like to use the K.I.S.S principle.
In doing so, I’ll typically calculate someone’s total energy expenditure by multiplying their bodyweight by 14-16 calories per pound. This calculation pans out for most people and it’s not something to view as a rigid formula.
If you’re more active than most or if you have a hard time gaining weight, lean towards the high end of the spectrum or change it all together. Something like 16-18 calories per pound may be what the doctor ordered in your case.
On the flipside, if you’re more sedentary than most of have a very hard time losing weight, lean towards the low end of the spectrum. Something like 12-14 might be ideal for your situation.
Either way, what you select as your starting point matters little. The entire point is to base your caloric intake on how your body and weight is responding to your initial calculation.
Metabolism (energy expenditure) is not a static measure and therefore neither should your caloric intake be. It’s a process and that’s what most people miss. This process is consistent regardless of what method you use to determine your initial energy expenditure.
The process would look something like:
1. Estimate total energy expenditure.
2. Set your caloric intake at a level above or below the above estimation depending on whether you want to gain or lose weight, respectively.
3. Track your measurements, weight, body fat, etc every 2-4 weeks.
4. Based on the trend you’re seeing with your tracking, adjust your intake accordingly.
5. Rinse and repeat steps 2-4 until you a) reach your goal or b) your goals change.
Because I enjoy beating dead horses, let’s look at an example. Jane weighs 130 lbs. She is spends about an hour each day exercising and doesn’t feel her metabolism is off-the-charts slow. She calculates her total energy expenditure by multiplying 130 by 14 to give her 1,820 calories. She understands that we’re working with estimates so she drops that number to 1,800.
Her goal is to drop 5 lbs of fat while preserving muscle. She’s not looking to do anything extreme in terms of dieting but she knows she needs to eat less energy than she expends. She reasons that a deficit of 25% would be suitable.
Multiplying 1,800 by 25% gives us 450. To start her “plan” she'll aim for between 1,300 and 1,400 calories per day.
She’ll also figure out her baseline data by weighing herself first thing in the morning after relieving herself. She’ll use a soft tape measure to measure the circumference of her arms, chest, navel, waist, hips and thighs. If she has the available tools, she might measure her body fat percentage. She’ll also take some pictures of herself.
After a handful of weeks eating between 1,300 and 1,400 calories she’ll re-measure the above variables. If they’re heading in the desired direction she’ll stay the course. If she finds that she’s losing weight too quickly, she’ll adjust her intake upward by 10% or so. If she finds that she’s not losing enough, she’ll adjust her intake downward by 10% or so.
And that’s the process. Next time you or someone you care about is frantically searching for the perfect calculation for energy expenditure, stop them and explain the process. If you use the wrong calculation, the process will uncover that fact and you’ll make the necessary adjustments over time to get on track.
Although this article is primarily about how to calculate caloric needs, it’s important to mention that the types of foods that comprise your calories are vitally important as well. That’s beyond the scope of this article however.
