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Calculating A Weight Loss Deficit

February 15, 2019 by Sayan


Once you know your total daily energy expenditure (TDEE) using the BMR (Basal Metabolic Rate) and Harris Benedict calculation, you know how many calories you need to eat to maintain your bodyweight.

Let's say the man with a BMR of 1947 calories is John, a 30 year old associate in hedge fund operations. He works at his desk between 10-12 hours every day, and gets no formal exercise, except for some lifting 2x a week for 30 minutes. He's not all too overweight, but realizes he needs to drop about 20 pounds to "really" get in shape and in his own words "look good on the golf course".

Since he's on the lower side in regards to exercise, we'll characterize his activity level as sedentary.

So we multiply 1947 * 1.2 from the chart above, to find that it takes about 2336 calories per day for John to maintain his weight.

From here, John needs to use a simple percentage deficit to lose weight. (Note: you can easily use the calculated deficits in the Excel bonus calculator.)

John's a smart guy and figures he'll start at a 20% deficit from maintenance, which will let him lose weight at a steady rate, without eating into his lean muscle.

So, using his 2336 maintenance intake level, he does the following calculations:

2336 * .20 (for 20% deficit) = 467 (daily calorie deficit)

2336 - 467 = 1869 calories per day

So, John starts eating 1869 calories per day on the lower-carb, insulin resistance "starter" plan, and ends up dropping 16 pounds in 2 months. He's now within 4 pounds of being ultra-lean. He loves how he feels, and loves the way his office coworkers keep blabbing about "how amazing you look".

This new-found confidence shines in the boardroom. He convinces the executive team to follow through with a breakthrough operations plan he's been working on. And when the plan turns out to save the firm $300,000, the board decides John deserves a raise and his very own corner office. Not too shabby for a guy who just wanted to "look good on the golf course"!

The Most Accurate Calculation: Katch-McArdle

While calculating your BMR and using the Harris-Benedict Formula is an outstanding starting point, if you're ready to get super-serious about your goals, I would use the Katch-McArdle formula. (This is in the Excel bonus calc, under the option "Know Body Fat % and Less Than 30 Lbs. to Lose")

This is a slightly different calculation that takes lean body mass (also called LBM) into
consideration. This means you need to know your body fat percentage, using inexpensive calipers or other devices, before you can use this calculation. (Instructions on calculating body fat % in later chapters.)

First, you need to know your LBM, which is how much you weigh without fat.

This is a fairly easy thing to do: If you know your body fat percentage, you take your total weight in pounds, subtract the percentage that is fat, and that's your LBM.

This time, let's use the example of Carol, a 57 year VP of Human Resources at a technology firm. She has quite the busy schedule, but usually makes it out of the office around 6 p.m., twice a week. On these 2 days and every Saturday, she decides to take up some resistance training to keep her body fit and mobile, while also keeping sane during some big projects and some *ahem* pain-in-the-butt coworkers at the office.

She weighs 160 pounds and uses handheld calipers to determine her body fat, which is 35%. She then knows she has 56 pounds of fat on her, because 160 x 0.35 = 56.

Then, she subtracts 56 from 160, for an LBM of 104. 

Now that Carol has her LBM, she jumps right into the Katch-McArdle formula: 

BMR = 370 + (9.79759519 x LBM.)

(That number only looks scary because you've forgotten you have a calculator right there on your computer!)

Let's go back to Carol. She has an LBM of 104, so she plugs it in:

BMR = 370 + (9.79759519 x 104)
BMR = 370 + 1018.95

Now she rounds up to the nearest calorie:
BMR = 370+1019 = 1389

And finds that her BMR (how much she burns just going about her day) is 1399 calories.
From here, she uses the same metrics as Harris-Benedict to find the TDEE, or Total Daily Energy Expenditure:



Sedentary (little or no daily exercise AND you do not have a

physical job)


Lightly Active (exercise at least 40 minutes, 1-3 days/week

AND you do not have a physical job)


Moderately Active (exercise at least 40 minutes 4-5 days/week

AND you do not have a physical job.) OR (little or no daily

exercise but you have a physical job)


Very Active (exercise at least 40 minutes 6-7 days/week AND 

you do not have a physical job) OR (exercise at least 40 minutes,

1-3 days/week AND you have a physical job)


Extra Active (exercise at least 40 minutes 6-7 days/week AND

have a physical job OR exercise at least 80 minutes 6-7

days/week and do not have a physical job)


Calculating A Weight Loss Deficit

Since she is working out 3 times a week and works a desk job, we'll use the "lightly
active"/1.375 multiplier.

1.375 * 1389 = 1910 calories per day to maintain her weight

Same as before, she uses a standard deficit percentage. She decides she wants to get fit and trim faster (and acknowledges that she has quite a bit to lose to get there), so she opts for a 30%
deficit (lowest deficit before muscle loss can become a big problem.)

1919 * .30 = 573

1923 - 573 = 1350 calories per day

Just like John form above, she starts on a lower-carb, insulin resistance "starter" plan, which she does for about 4 weeks. She loses 8 pounds in less than a month, and then decides to increase carbs a bit (to give her some fuel for resistance workouts). She updates her weight and bodyfat % in the "primary fat loss" sheet in the Excel bonus calculator, and goes forward for the next 3 months. She sticks to her calories, gets good rest, and works out consistently...and within 4 months she is down a total of 31 pounds!

She feels amazing, loves her new body, and looks likes she's in her late 30s when she's actually 57. Best of all, she occasionally catches guy nearly half her age doing the "double-take" look as she walks by...and she can't get enough of it! Not bad for a few months on the plan. 

*Note: John and Carol are fictional people, but their stories are based on people using similar plans.
4 Rules for Optimal Caloric Success

1. Never eat less than 1200 calories a day. If you eat less than 1200 calories a day, your body will freak out and launch the best tool it's got for preventing death by
starvation: Cortisol. Cortisol is a stress hormone that causes you to retain your fat
and cannibalize your muscle in a process called catabolism. You'll lose weight, but
you'll get "skinny-fat," which will leave you looking kind of saggy and dumpy.
Eventually, your body will grind your metabolism to a halt and your weight loss
efforts will start making you get fat. Sounds counterintuitive, but it's true.

2. Use the deficits below to determine how quickly you want to lose weight:

If you want to lose fat...

Maintain a deficit of...

Slowly (saves the most muscle) 

15% below maintenance/TDEE

Semi-Moderately (best starting point if you're no more than 25 lbs. overweight)

20% below maintenance/TDEE

Moderately (best starting point if you have more than 25 lbs. to lose, but you're not obese.)

25% below maintenance/TDEE

Quickly (this potentially eats into your lean muscle unless you are obese, and is not recommended for people at a healthy weight.)

30% below maintenance/TDEE

3. Do not go past 30% below your daily maintenance/TDEE unless you have 40+
pounds to lose. If you go past 30%, you're at a high risk of muscle loss and other
metabolic issues. By the time you get to 50%, you're near starvation levels and
maintaining an unhealthy, potentially dangerous lifestyle. 30% below maintenance is
the bottom level at which it is safe to lose weight - anything beyond that is not only
ineffective and unhealthy, but could actually be counterproductive by causing your
body to go into starvation mode.
a. Note: People who have 40+ lbs to lose and/or are obese don't have to worry
about going too low (as long as it's not below a 50% deficit). As research has
proven, when you have a very large amount of body fat, the body has no
choice but to burn off more of it than it burns off muscle.

4. The more you burn at the gym, the more you get to eat later. If it's the Fourth of July
and you know you're going to eat an extra hamburger at the barbecue that night, you
owe it to your past and future selves, who are working really hard to lose weight, to
put in the extra weight at the gym to earn that burger. Just don't go too crazy and
throw yourself out a deficit for the week!

Why You Should Eventually Quit Counting Calories

Here's a secret most fitness models won't tell you: They don't count their calories.

Now, you might be upset, and rightly so, that you just had to learn all about how to count calories if those marble-carved people you see in the magazines don't have to do it.

But we've gotten ahead of ourselves:

Fitness models and body builders don't count their calories because they already know what portions of which foods equal what amount of calories. They've become such pros at counting calories - and have fine-tuned their own diets and meal plans so meticulously - that they can just calculate these things on the fly.

The point of telling you all of this is to give you hope - you only have to maintain that food journal in the beginning of your weight-loss exodus!

If you're eating clean, eating healthy and exercising regularly, you'll eventually learn what foods (and how much of them) you can eat and still stay within your maintenance goals, and then life will get simple again.

The only time you'll have to count calories is when you eat something out of the ordinary, like on a cheat day, and if you've made positive lifestyle changes, you won't have to do that too often.

This is one of the basic lessons we all learn early in life: Nothing good comes easily; if it was easy, you wouldn't value it, anyway.

Interested in losing weight? Then click below to see the exact steps I took to lose weight and keep it off for good...

Read the previous article about "The Easy Way To Determining Your Calorie Intake"

Moving forward, there are several other articles/topics I'll share so you can lose weight even faster, and feel great doing it.

Below is a list of these topics and you can use this Table of Contents to jump to the part that interests you the most.

Learn more by visiting our website here: invigoratenow.com