How Much Should I Eat In A Day? Plenty.

9 Nov

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.

food vacuum

The Method

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

The Madness

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.

food glorious food


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?


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9 Responses to “How Much Should I Eat In A Day? Plenty.”

  1. Jessie November 9, 2011 at 3:38 am #

    I am confused… or maybe just ridiculous… I’m not understanding the directions… I have a number over 4000 which doesn’t seem right… I multiply by 1.3, then 24 then 1.3 again? HELP!

    • melruns November 9, 2011 at 3:42 am #

      Haha okay. So basically, once you’ve got your resting metabolic rate at step 3, you need to get 30-35% of that total and add it in to factor in everyday activity. So the easiest way to do that is to just multiply it by 1.3 or 1.35. If you’re getting over 4000, make sure you’re starting with your fat free mass, not your total weight–that could possibly be where the problem is.

  2. Jessie November 9, 2011 at 3:39 am #

    oh wait… didn’t subtract the initial number from my weight… let’s try again.

  3. Eleanor@Eatinglikeahorse November 9, 2011 at 8:07 pm #

    This is so interesting! I agree that BMI is a bit useless for those reasons and body fat percentage is a much more useful indicator… I never knew how to calculate calorie needs though – great post :-)

    • melruns November 10, 2011 at 1:56 am #

      Thanks Eleanor! It’s amazing how much info there is about there about the “right” number, and it’s all based on a mythical woman creature that has nothing to do with your own body. Glad it helped :)

  4. Mike December 19, 2011 at 4:38 pm #

    ~3200 sounds about right. It’s hard for me to stick to a hard number though since my calories burned through activity swing widely from day to day based on my training schedule. One day I might run 12 miles (~1500 calories) and the next zero miles, so that could be 4400 calories one day and then 2900 the next.

    I realize I have the luxury of a marathoner’s metabolism, but I’ve been finding luck with moderation and common sense (trying not to sound holier-than-thou). What I mean is, regardless of my caloric needs, like most people I’m probably going to be in trouble with a pizza-milkshake or deep fried cheese burger (or the chicken and waffle taco I had yesterday). But making smart choices most of the time should be enough for most people, which is also a lot more accessible than keeping track of exactly how many calories they’ve eaten.

    But I know people like numbers, so this is a great tip for finding out what you need. I bet it’s also a huge wake up call for some who find their caloric need is on the order of 2000-3000 and they have a monster thick burger from Hardee’s, with fries and a Coke for 2500 calories in one sitting.

    As always, thanks Mel!

  5. pillows May 20, 2012 at 5:10 am #

    HA!! Thank you!! I started running last year and am up to 21-28 miles a week. At first I dropped 10 lbs(I am a vegetarian) but then noticed that I started carrying weight in my hips and thighs. So, I found a website that “calculated” my calrories/fat/protein/carb intake for my running. I followed it and nothing came off my hips/thighs… So, I found another website that said I wasn’t eating enough and my body was carrying “fuel” like a camel…haha..THAT made more sense…I searched again for answers and found your website. So, after doing the formula above I realized I was eating 50 calories more that my So, I am happy to say that my “fuel stores” have reduced slowly over the past month. thank you, thank you, THANK YOU!!! :-)

    • melruns May 20, 2012 at 2:19 pm #

      I’m glad you stumbled upon this formula!! Isn’t it so nice to know that more food = better? :) And congrats on kicking ass a new runner. That’s pretty impressive mileage!

  6. Chanell Polizzi June 10, 2013 at 2:40 am #

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