Based on the pictures of example body fat percentages for males, I’d guess that I am about 9% body fat. My fasted body weight (measured in the morning) is 170 pounds.
So let’s plug these numbers into the Katch-McArdle equation:
BMR = 370 + (21.6 x LBM), where LBM is your lean body mass in kilograms
First, I need to know my LBM. LBM is simply your total body weight minus fat weight.
So, my lean body mass (LBM) = 170 pounds x (100% - 9%)
LBM = 170 pounds x 91%
LBM = 170 pounds x 0.91
LBM = 154.7 pounds
So now I have my LBM in pounds. But for the equation, we need LBM in kilograms. There are about 2.2 pounds (lbs) in a kilogram (kg). So to find my LBM in kilograms, I must divide 154.7 pounds by 2.2 (pounds per kilogram).
So, my LBM is 70.2 kilograms (kg).
Now I’ll plug this into the Katch-McArdle equation.
BMR = 370 + (21.6 x 70.2 kg)
BMR = 370 + (1516.32)
BMR = 1886.32
This means that my BMR is 1,886 calories.
Now that we’ve calculated our BMR, let’s calculate our activity burn.
Step 1B: Calculate Your Average Activity Burn per Day
Your energy balance each week, total calories consumed vs. total calories burned, is extremely important in achieving your fitness goals (i.e. cutting, maintaining, or bulking), but your daily energy balance can vary a bit as long as you are consistent over long periods of time.
In other words, your average energy balance over time matters most in achieving your fitness goals. Don’t sweat the small dietary road bumps. We all have them.
To calculate your Average Activity Burn per Day, you should first list all of the activities you do during a typical/average week and the amount of time you spend doing them.
For example, here’s what my average activity each week looks like right now:
Weight training day 1: Chest and calves (75 minutes)
Weight training day 2: Back and biceps (75 minutes)
Weight training day 3: Legs (75 minutes)
Weight training day 4: Arms and shoulders (75 minutes)
Weight training day 5: Chest and calves (75 minutes)
Weight training day 6: Legs (75 minutes)
Walking the dog (90 minutes per week)
StairMaster (60 minutes per week)
Cleaning the house (120 minutes per week)
After you have listed all of your total activity, we will now calculate the number of calories you burn from each of these activities.
When I calculate the activity burn for my clients and myself I use MET (Metabolic Equivalent) data for physical activities from "The Compendium of Physical Activities Tracking Guide" by B. E. Ainsworth.
Each individual activity from my database of over 600 activities has a MET value associated with it. A MET value represents the ratio of energy (i.e. calories) required to perform a particular activity relative to your BMR. My macronutrient calculator estimates your calorie burn by multiplying the MET value for your chosen activity by the duration time of your activity and by your calculated BMR.
Since I cannot easily share this database with you, please use one of the following sites to calculate your activity burn for each of your activities.
My Fitness Pal Calories Burned From Exercise
Using these resources, I found my activity burn to be as follows:
Weight training day 1: Chest and calves (75 minutes) = 485 calories
Weight training day 2: Back and biceps (75 minutes) = 485 calories
Weight training day 3: Legs (75 minutes) = 485 calories
Weight training day 4: Arms and shoulders (75 minutes) = 485 calories
Weight training day 5: Chest and calves (75 minutes) = 485 calories
Weight training day 6: Legs (75 minutes) = 485 calories
Walking the dog (90 minutes per week) = 230 calories
StairMaster (60 minutes per week) = 620 calories
Cleaning the house (120 minutes per week) = 300 calories
Now, add all of your activity burn calories together to arrive at your Total Activity Burn per Week.
My Total Activity Burn per Week is 4,060 calories.
Now remember, our goal is to determine our Total Daily Energy Expenditure (TDEE), so we need to know how many calories we burn per day from activity.
Your Average Activity Burn per Day is the average number of calories you burn each day from your total exercise per week (your Total Activity Burn per Week divided by 7).
My Average Activity Burn per Day is 580 calories (4,060 calories divided by 7).
So, we now know our BMR and Average Activity Burn per Day. We simply add these two numbers together to arrive at our TDEE.
My TDEE is 1,886 calories + 580 calories = 2,466 calories.
And that’s it!
Once again, this isn’t an exact science, but it is much more accurate that the online macro calculators that use general activity multipliers.
The 3 Principles of Body Composition
There are three foundational principles when it comes to building muscle and shredding fat that are well established both scientifically and anecdotally:
A caloric surplus is necessary for maximizing muscle growth
A caloric deficit is necessary for shredding fat
A high-protein diet is vital for both maximizing muscle growth and minimizing muscle loss while shredding fat
Caloric Deficit for Shredding Fat
You must burn more energy than you consume to achieve meaningful fat loss. This is called a caloric deficit (i.e. consume less calories than you burn).
However, eating very little, known as starvation dieting, isn’t ideal for weight loss. If your caloric deficit is too extreme, your metabolism will slow, you will lose muscle along with fat, and you’ll really hate the process.
Caloric Surplus for Muscle Growth
Contrary to shredding fat, you must consume more energy to achieve meaningful muscle growth. This is called a caloric surplus (i.e. consume more calories than you burn).
If you don’t eat enough calories, you will struggle to gain muscle. This is because a caloric deficit decreases your body’s ability to synthesize skeletal muscle proteins, reduces anabolic hormone levels while increasing catabolic hormone levels, and impairs workout performance which in turn impairs progression in your workouts and therefore muscle growth.
I recommend that you maintain a slight 10% caloric surplus when bulking. In other words, you should eat around 110% of your total daily energy expenditure to be in the “sweet spot” for gaining lean muscle.”
It is worth noting that most gym “newbies,” people with less than a year of weightlifting training under their belts, can build muscle and lose fat at the same time, but can’t optimally do both simultaneously. The rest of us will do best by alternating between periods of cutting and bulking.
Step 2: Determine Your MAIN Fitness Goal
Most people I know want to both shred fat and gain more muscle, but unless you are a newbie weightlifter, you cannot both shred fat and gain muscle at the same time.
Doing so would violate the 3 Principles of Body Composition. In order to maximize muscle growth, you must maintain a caloric surplus. In order to shred fat, you must maintain a caloric deficit.
So which one should you pick? Here’s my rule of thumb:
If you have a body fat percentage greater than 15% as a male, you should cut down to 10-12% before beginning to bulk (i.e. gain muscle). If you are a female with a body fat percentage greater than 20%, you should cut down to 15-17% before beginning to bulk.
If you are a male around 10-12% body fat or female around 15-17% body fat, then you’re ready to begin a lean bulk.
Starting to build muscle with a shredded physique is ideal for several reasons:
High body fat levels reduce insulin sensitivity, thereby suppressing muscle protein synthesis (known as MPS, which is a vital component of hypertrophy, the muscle growth process).
High body fat levels create imbalances in hormonal levels, causing testosterone levels to drop and estrogen levels to rise in men.
Bulking from a shredded physique until you reach 15% body fat as a man or 20% as a woman, then cutting back to 10-12% or 15-17%, respectively, saves you from long, grueling cuts.
So here’s the bottom line: body fat makes you fatter, makes it more difficult to build muscle, and creates hormonal imbalances. If your goal is to gain muscle, you should start with a lean physique, 10-12% body fat for men and 15-17% body fat for women.
Step 3: Determine Your Daily Calorie Target
Now that you have determined your main fitness goal, this step is easy. If you decided that it is time to shred fat, then you should aim for a 20% caloric deficit every day. Simply multiply your TDEE by 0.8 to figure out how many calories you should eat every day for fat loss.
For example, I am currently shredding. My TDEE is 2,466 calories, so my Daily Calorie Target should be 1,973 calories per day (2,466 calories x 0.8) to efficiently burn fat.
If I decided to start a lean bulk right now to build muscle, I would aim for a 10% caloric surplus every day. If you also want to lean bulk, simply multiply your TDEE by 1.1 to determine how many calories you should eat every day.
For example, if I stopped shredding and began a lean bulk, I should aim to eat 2,713 calories (2,466 calories x 1.1).
Step 4: Calculate Your Macros
Macronutrients, often referred to as “macros,” are substances required in large amount in the human diet. There are three primary macronutrients that the human body needs in order to function properly: carbohydrates, fat, and protein.
Regardless of the sources foodwise, 1 gram of protein contains 4 calories, 1 gram of carbohydrates contains 4 calories, and 1 gram of fat contains 9 calories.
Step 4A: Determine how much protein you should be eating
According to U.S. and Canadian dietary reference intakes, the recommended daily allowance for protein is 0.36 grams per pound of bodyweight (0.8 grams per kilogram of bodyweight) for healthy adults. This amount is “the average daily intake level that is sufficient to meet the nutrient requirement of nearly all [~98%] of healthy adults.”
As long as you are eating a calorically sufficient diet, this recommendation is extremely easy to meet.
However, many decades of research and anecdotal evidence proves athletes, particularly those who lift heavy weights regularly, need more protein than the average person.
Still, the truth is that I can’t tell you exactly how much protein you need. Only expensive nitrogen balance testing can tell you for sure. However, when it comes to fitness, people tend to fall into one of three groups. Here’s my simple chart:
