Calculating your caloric needs
 

This post is not meant to be rigorous, but rather a starting point for further discussion.

Weight change = Caloric input - caloric output

Calculating caloric output:

You have a BMR (basal metabolic rate) = how many calories your body uses just to survive every day. This figure is typically dependent on factors such as your sex, weight, lean mass, age, etc.

But you do more than just survive -- you move around, too. As you move your body throughout the day, you burn additional calories (which I'll call DAE = Daily Activity Expenditure) on top of your BMR. This sum gives you your TDEE, or Total Daily Energy Expenditure.

One popular method is to estimate your BMR using some regression formulas and then apply an activity multiplier (which I'll denote with m) to estimate how much you expend in terms of activity. Note that these are "ballpark" approaches that simply give you a realistic starting point.

So TDEE = BMR + DAE = BMR + m*BMR

BMR formulas:

Weight is in kg, height is in cm, age in years:

Mifflin-St Jeor Formula:
For males: BMR = 9.99*Weight + 6.25*Height – 4.92*Age + 5
For females: BMR = 9.99*Weight + 6.25*Height – 4.92*Age -161

Katch-McArdle Formula:
BMR = 370 + 21.6*LBM (LBM is your lean body mass -- i.e. not fat, in kg)

(In general, people say Katch-McArdle is the best one if you know your bodyfat percentage, but if not, then Mifflin St. Jeor is probably better, but it tends to overestimate your BMR if you're overweight).

DAE Multipliers:

Then to estimate your DAE, apply the most relevant multiplier (m) to your BMR:

0.2x = Sedentary (Desk job, little exercise, etc. If you spend most of your time on your ass, really)
0.3x-0.4x = Lightly Active (Light daily activity and light exercise 1-3 days a week / someone on their feet most of the day like a teacher or retail worker)
0.5x-0.6x = Moderately Active (Moderately daily activity & moderate exercise 3-5 days a week / someone moving around a lot like a busy waiter)
0.7x-0.8x = Very Active (Physically demanding lifestyle & hard exercise 6-7 days a week / perhaps working in hard labor all day)
0.9x-1.2x = Extremely Active (Athlete in endurance training or very hard physical job)

From here, you just do TDEE = BMR + DAE and that's your daily output measured in calories.

Calculating caloric input:

Add up the number of calories from all the food you eat.

Re: Calculating your caloric needs
 

Since

Weight change = Caloric input - caloric output

This means you can either raise/lower your input, or raise/lower your output. So for losing weight...



If you are aiming to lose weight, one rule of thumb is to create a deficit equal to 20% of your TDEE (similarly, 20% surplus for gaining weight).

So if your TDEE is 2000 calories, and you wanted to lose weight, you might consider a daily deficit of .2*2000 = 400 calories. This means you can either eat 400 fewer calories per day than you normally do, or exercise more such that you burn 400 extra calories per day. Most people do a combination of both.

A pound of fat is 3500 calories. So this means if you hold a 500-calorie deficit for a week, you lose a pound of fat. One general rule that gets thrown around a lot is that you should try not to lose more than 2 pounds a week (1000-calorie deficit/day) unless you have a very high bodyfat percentage (30%+), because by that point you are likely to lose lean mass (i.e. muscle) in addition to fat, rather than just fat as desired.

The more accurate way to gauge your caloric needs is through trial and error -- tracking your calories and weight and activity and seeing how your weight changes over time. From there you can either eat more/less or work out more as needed.

Re: Calculating your caloric needs
 

If I've said anything inaccurate please correct me

Re: Calculating your caloric needs
 

How about you focus on setting athletic goals instead of micromanaging your diet

Re: Calculating your caloric needs
 

Managing your diet is an integral part of setting athletic goals. Figuring out how much your body needs vs. how much you're eating vs. how much energy you're expending is a pretty basic concept.

Re: Calculating your caloric needs
 

It's nowhere near as vital as people make it out to be

Re: Calculating your caloric needs
 

That depends entirely on your goals. This isn't a black and white issue.

If you goals are athletic in nature obviously focusing on athletic goals should be your priority.

If gaining or losing weight is your goal, diet is extremely important and one of the biggest and most common oversights of newbies to fitness. I see it so often it's painful.

Re: Calculating your caloric needs
 

As far as the DAE multiplier what if you have moderately daily activity and little/no exercise?

I have a physically demanding job but outside of it I don't work out except once or twice on the weekends when I play tennis. How'd I figure out the multiplier for that?

Re: Calculating your caloric needs
 

"Lightly active" usually corresponds to people who spend a lot of their day on their feet, like a teacher or retail worker. It's basically doing the bare minimum to avoid being sedentary.

"Moderate" might be something where you're not only on your feet a lot, but you're also doing a lot of moving (like a waiter, etc).

If you've got a demanding job and you also do a little tennis, my guess would be "Moderate" and I'd start somewhere around there.

But really, you can also count your calories for a while and see how your weight changes in turn, and get a better sense for what your real TDEE is.

Re: Calculating your caloric needs
 

For sure

Re: Calculating your caloric needs
 

question for this... can you only gain muscle on a calorie surplus?

Re: Calculating your caloric needs
 

Yes.

Think of it in terms of physics. You're creating new mass. Mass is energy. That energy has to come from somewhere. It comes from food. The excess energy from food after your other caloric needs are met is literally converted into muscle.

Someone astute might ask though, "Why can't fat energy be used to build muscle"? The answer to that is complicated, and generally can only happen when you're severely overweight, as the body has evolved to never want to do this (because it involves burning a fat surplus and the body would much rather store fat than burn it).

Re: Calculating your caloric needs
 

ah yea, thats what i thinking... so its bullshit when people say that its harder for skinny people to build muscle

Re: Calculating your caloric needs
 

Absolutely. If anything it's easier, since they have less muscle, which means they will build muscle faster.

'hard gainers' are just people that don't eat enough food to bulk. They usually overestimate how much they eat because they often have small appetites.

Re: Calculating your caloric needs
 

Thank you so much for posting this information, Marcus.

I've recently come to the realization that I'm not happy with my weight, and these guidelines are a great thing to follow. The result of the equation does seem high for me, unless I calculated wrong (converted: 83.9146 kg, 177.8 cm, and 22.83 for age because I'm about two months from my birthday at 0.4x DAE = 2579 cal).

As far as the multiplier -- if I'm starting a routine on going to my apartment's fitness center in the mornings (mostly for cardio) every other day for a minimum of an hour, should I apply a multiplier of 0.4x or 0.5x for the DAE? I'm currently out of work, so I'm spending my time at home taking care of my two kids. I'm personally thinking 0.4x, just to be safe.

Either way, I'm trying to hover around 1700-1800 calories when I go to the fitness centers in the morning, and 1500-1600 when I'm not. Is this realistic? I don't seem to be having too many issues keeping my calorie intake low.

Re: Calculating your caloric needs
 

If you're trying to lose weight, keep it simple at your size and eat 2000 or less calories a day.

Track your weight, but I don't think you will have any problems in the 1500-2000 range and you should get results relatively quickly.

Re: Calculating your caloric needs
 

Alright, that sounds great.

Thanks, Reach.

Re: Calculating your caloric needs
 

Ehh I use SparkPeople and I think it's pretty accurate at determining the amount I should eat every day.

And I used this to determine my body fat percentage which also helped me find out my lbm: http://www.bmi-calculator.net/body-fat-calculator/

I always thought the amount of food I ate wasn't a big deal but after I started tracking my meals more regularly I noticed how much I was overeating all the time. But now I've gotten to the point where I eat just enough or sometimes not enough but I feel full for the day which is great. Drinking a lot of water throughout the day helps too.

tldr tracking calories is important

Re: Calculating your caloric needs
 

I break everyrule in this formula >.> i barely eat a gorenola bar a day and im never hungry, and im 6'2,male,210,and do carpentry from 8am - 5 pm everyday :P

so it makes noooo sense xD

my calorie intake is to low :P

Re: Calculating your caloric needs
 

So what you're saying is you're dying