Today I took my second test in personal trainer school: all about nutrition. One of the most helpful things we learned is how to best calculate metabolism as it translates into calories needed. It turns out I need about 2,000 calories a day to maintain my activity and my weight. No WONDER I’m a human food vacuum (most similar to a roomba robot that zooms around all day into every room looking for something to suck up). Getting your metabolism number is easy, it just takes one critical measurement and one formula.
In order to figure out your metabolism–and whether you’ve got the needs of a roomba like me
–the key is finding your fat free mass. This means knowing what your body fat percentage is, turning it into pounds, and then subtracting it from your total weight. That number is key to synching up with your body composition–which is why the generic Body Mass Index chart generally sucks. If you’re a bodybuilder (not I, but say, the Arnold), and you look up your BMI using height and weight, it will show you as obese. Clearly, that’s inaccurate.
By calculating your metabolic rate based on your body composition, it gives you a much more accurate read. Once you get your body fat percentage (read about two ways to do that here, or my two tips below) you can follow this formula to figure out what your body needs:
- Multiply your bodyfat % by your weight. Then subtract that number from your weight. What’s left is your fat free mass–basically everything that is not fat like muscle, organs, etc.
- Fat free mass/2.2 to turn it into kilograms
- That number x 1.3 x 24 gives you your resting metabolic rate (RMR) which is the amount of calories your body needs to lay very very still all day
- Multiply your RMR by 1.35 to factor in everyday activity (1.4 for guys)
- That number + 200 or 300 cals if you’re working out regularly each week
- Aaand THIS number, would be the total calories you need in a day. Bam. Slam. Wham.
- At this point you can either add 350 cals if you’re looking to gain muscle, or subtract 500 cals to lose 1 lb. a week
Phew! Looks very annoying, huh? But with a calculator it’s super easy. I was actually pretty shocked to find out I needed about 2,000 calories–2,061 to be exact. Since weight became a “thing” in high school (right about prom time, did anyone else experience that?) and I started reading health and fitness magazines, 1,200 and 1,500 calories are the only magic numbers I would see. I thought that’s what a girl needed to eat to be healthy. And sometimes it is if a person is trying to lose weight, but what about when you want to just “be”? I for one, will enjoy all 2,000. May it be filled with all the peanut butter, chocolate, eggsfruitfishoatmealbaconteddygrahams a girl can eat.
Making It Accessible
Most of you are probably thinking–I don’t have access to the tools I need to get my body fat percentage! This is useless! Gahhh! But stress not, I’ve got two tips for you: 1) go to a gym and sign up for just one personal training session. It will cost you $60-$80, but they’ll do your full assessment, and you can walk out informed, or 2) there are scales that actually use the same technology as the handheld bio-electrical impedance analysis calculator, and if you stand on it to weight yourself it will also give you a readout of your bodyfat. It’s not the most accurate, but it’s good enough to get an idea and work up your estimated daily metabolism. Just google “bodyfat scale” and a bunch will show up, many of them under 20 bucks, too. Sweet deal. I kinda want one.
So… what kind of vacuum are you?