How To Calculate Calories to Lose Weight Fast

If you want to lose weight as fast as possible then the most important thing to focus on is eating the right amount of calories in the right ratios of the three macronutrients, protein, carbohydrates, and fat.

This principle is based on the first law of thermodynamics which states that energy cannot be created or destroyed in a closed system and only converted to another form.

The energy we take in and expend from food is measured in the form of a calorie which is a unit of heat energy.

The calories we take in and the calories we expend determine our energy balance and whether we release energy and lose weight or store energy and gain weight.

Although there've been increasingly precise scientific measurements of energy systems over the last few decades there have still not been any exceptions found to this law, it's as close to a scientific fact as you can get.

In previous articles I've explained that there are two types of weight you can lose. Fat mass and lean mass.

Fat mass is your body fat and lean mass is made up of your muscle, bone, water, and organs.

Sometimes you may hear lean mass referred to as fat free mass because it consists of everything in your body except for fat. So of course, the only type of weight we want to lose is body fat.

There are more factors that influence this calories in calories out energy balance equation than just eating and physical activity. There are 2 main factors that influence energy in:

1) Caloric Intake- calories we take in through eating food.

2) Caloric Absorption- it's estimated by researchers that 95% or more of the calories we intake is actually digested and absorbed.¹

Then, there are 7 main factors that influence energy out:

1) Body Size- The bigger a person is the more calories burned since they typically have more muscle and larger organs. The combined energy expenditure of the heart, lungs, kidneys, brain and liver represents approximately 80% of Total Daily Energy Expenditure (TDEE). These organs have a metabolic rate that is 15-40 times greater than their equivalent weight of muscle and 50-100 times greater than fat tissue.

2) Muscle Mass- the metabolic rate of muscle tissue is estimated to be about 4.5 to 7 calories per pound, whereas the metabolic rate of fat is about half of that. So, more muscle mass leads to more calories burned.³

3) Sex- Men are typically bigger than women and have more muscle and larger organs therefore men expend more calories.

4) Age- Muscle mass decreases approximately 3–8% per decade after the age of 30 and this rate of decline is even higher after the age of 60.⁴  This is why it's absolutely essential to strength train consistently each week.

5) Physical activity- energy burned through exercise and non-exercise activity.

6) Thermic Effect of Food (TEF)- The energy used to digest the food we eat represents about 10% of daily calorie expenditure. Whole foods require more energy for digestion than processed foods.⁵

7) Hormonal Status- certain hormones like insulin signal the body to store energy while other hormones like thyroid hormone signal the body to release energy.

So, the old adage of "eat less, move more" is a bit of an oversimplification.

Along with consuming the right amount of calories for fat loss, the ratios of the macronutrients protein, carbs, and fats you eat are important to consider as well because they influence the Thermic Effect of Food, your hormonal status, and the type of weight you lose or gain, whether fat mass or lean mass.

Each macronutrient has a different Thermic Effect of Food:

• Protein provides 4 calories per gram, and its TEF is 20–30%.
• Carbohydrates provides 4 calories per gram, and its TEF is 5–10%.
• Fat provides 9 calories per gram, and its TEF is 0–3%.⁶

So, protein burns the most calories through digestion, while carbs burn the second most, and fats burn the least.

If you don't eat enough protein you'll lose significant lean mass because the body has no reserve for protein other than muscle and lean tissue.

Protein deficiency also:

• Impairs all organs⁷, especially the kidneys.⁸
• Downregulates immune function, resulting in higher risk of infection.⁹
• Makes the gut permeable, increasing the risk of infectious invasion.^{10 11}

If you eat too much protein the excess protein will be metabolized for energy or converted to glucose, which can then be converted to fat if there is a significant enough excess, but either way nitrogen is released and nitrogen forms the toxin ammonia so eating too much protein can cause ammonia toxicity.¹²

Eating too much protein can also cause toxins like amines and hydrogen sulfide to be generated from gut bacteria as gut bacteria can ferment protein.^{13 14}

So, eating the right amount of protein decreases the loss of muscle mass, maintains, or even increases muscle mass, especially if you are strength training, prevents fat gain, and encourages proper organ function, immune function, and gut health.

If you eat too many carbs, specifically starchy carbs and sugars, glucose (blood sugar) levels can rise excessively and an excess amount of glucose in the bloodstream is toxic to the brain, neurological, and cardiovascular systems so the hormone insulin is released from the pancreas to decrease blood sugar levels and drive the excess glucose into the muscle and liver cells as glycogen.

Glycogen is simply the stored glucose in muscle and liver cells and its storage space is limited. The average person can store around 600 grams of glycogen (about 500 grams in muscle cells and about 100 grams in liver cells) which is 2,400 calories since 1 gram of carbohydrate contains 4 calories.

So, if glycogen stores are already full and the excess glucose cannot be properly metabolized by the mitochondria because fat consumption is above roughly 30 percent of total calories, then much of the excess glucose can be converted into fat and driven into the fat cells.

Obesity, Diabetes, and poor blood lipid profiles, which is the measure of cholesterol and triglycerides in the blood, and are risk factors for heart disease, are developed when this happens chronically.¹⁵

If you don’t eat enough carbs mitochondrial energy production will be significantly decreased, so you'll have lower energy levels, because glucose is the primary and preferred fuel source for all the cells of the body, especially the brain and neurons.

And the body won't have enough stored glycogen which is the primary fuel source used during high intensity exercise. In this scenario, the body will manufacture glucose from protein, a process called gluconeogenesis, and since protein reserves are found in muscle and lean tissue this can lead to a loss of muscle mass.

So, eating the right amount of carbs prevents excess body fat gain, chronically high blood sugar levels, obesity, diabetes, a poor cholesterol profile, and muscle loss while maximizing energy levels, cognitive function, and providing sufficient fuel to muscles for high intensity exercise.

If you eat too many fats the excess amount will simply be stored as fat. Furthermore, if this excess consumption of fat is mostly from polyunsaturated omega 6 fats which mostly come from vegetable and seeds oils and poultry mostly fed grains this will lead to excess inflammation and lipid peroxidation, the oxidative degradation of lipids, causing damage to mitochondria which produce most of the energy in your cells.

This leads to rapid fatigue, decreased physical endurance, and often reduced physical activity which can further contribute to fat gain and obesity.¹⁶ Lipid peroxidation also damages Low Density Lipoprotein (LDL) particles and creates oxidized LDL, a major factor in atherosclerosis and heart disease.

Monounsaturated and saturated fats do not have these inflammatory or toxic effects even in large amounts.

If you eat too little fats, specifically monounsaturated and saturated fats, you won't be providing the body with the core structural fats that make up 75 to 80 percent of the fatty acids in most cells.

You'll likely be deficient in fat associated nutrients like choline and Vitamin A and lack sufficient omega 3 fats for a healthy inflammatory response.

These fats also serve as building blocks for hormone production like testosterone which promotes muscle growth and growth hormone, which is the main muscle promoting hormone, so monounsaturated and saturated fats allow for increases in muscle mass.

Monounsaturated fats and saturated fats both lead to improvements in blood lipid profiles and decrease the risk of heart disease.

Saturated fat has often been associated with increased risk of cardiovascular disease but a meta-analysis from 2010 of epidemiological and prospective cohort studies concluded that "There is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD (Coronary Heart Disease) or Cardiovascular Disease (CVD)."¹⁷

Saturated fat consumption actually improves lipid profiles by increasing levels of protective High Density Lipoprotein (HDL) cholesterol and making LDL particles larger, protecting them from glycation and oxidation which reduces the level of atherogenic oxidized-LDL.

Saturated and monounsaturated fats also contribute to lower triglyceride levels, which is a form fat found in the blood. Triglyceride levels are mostly determined by carbohydrate consumption and insulin level as insulin inhibits the removal of triglycerides from the blood. ¹⁵

So, eating the right amount of fats and the right types of fats prevents excess body fat gain, inflammation, lipid peroxidation, mitochondrial damage, obesity, and heart disease while providing the body with its secondary energy source, the building blocks for proper cell and hormone production, a healthy inflammation response, and increased muscle mass.

So now that you understand why it’s so important to consume the right amount of calories and macronutrients, I’m going to take you through the steps to calculate them together. There are 3 steps to calculating how many calories you should eat for fat loss.

Step 1- Calculate your Basal Metabolic Rate (BMR)

Your BMR is the amount of calories your body burns at complete rest to maintain it's vital functions and is determined mostly by your muscle mass, height, weight, age, and sex.

There are multiple formulas used to calculate BMR but the formula most widely believed to provide the most accurate result is the Mifflin-St Jeor equation. There are many online calculators that use this equation, and you can simply enter in your sex, age, height, and weight, and it will calculate your BMR for you.

I typically use the Omni Calculator for Basal Metabolic Rate. You can also enter your information into the actual Mifflin-St Jeor equations below and calculate manually. There is one for men and one for women.

Men- BMR (kcal / day) = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) + 5

Women- BMR (kcal / day) = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (y) - 161

So, for example if you’re a 45 year-old male at 5 foot 8 inches tall and 185 pounds your estimated BMR is about 1,700 calories.

Step 2: Calculate Total Daily Energy Expenditure (TDEE)

If you have an activity tracker you can use that to estimate how many calories you burn per day from physical activity or you can multiply your BMR by the appropriate activity factor below.

Activity Factors:

Sedentary (little to no exercise + work a desk job) = Multiply your BMR by 1.2

Lightly Active (light exercise 1-3 days / week) = Multiply your BMR by 1.375

Moderately Active (moderate exercise 3-5 days / week) = Multiply your BMR by 1.55

Very Active (heavy exercise 6-7 days / week) = Multiply your BMR by 1.725

Extremely Active (very heavy exercise, hard labor job, training 2x / day) = Multiply your BMR by 1.9

So going back to our example, let’s say he's lightly active, we would simply take his BMR of 1,700 and multiply by the corresponding activity factor of 1.375 which gives him an estimated Total Daily Energy Expenditure of 2,337 calories.

Step 3: Subtract 200-500 Calories from TDEE

Metabolic research has determined that one pound of fat is equal to 500 calories, so oftentimes people will create a deficit of 500 calories per day with the goal of losing 1 pound per week. This can work for some people especially if they are larger in body size but for most average sized adults this can be an unsustainable deficit.

The most important factor is never decreasing your calorie intake to less than your BMR, which again is only the amount of calories your body needs at complete rest to perform vital functions.

If you did eat less than your BMR you would cause dysfunction in all of the systems of your body, create an imbalanced hormonal profile, significantly slow down your metabolism, and lose significant lean body mass. This is why starving yourself to lose weight is a major mistake and whatever weight you do lose will quickly be regained when eating normally again.

It's best to choose a deficit that is sustainable for you and prevents excessive hunger and fatigue that can be experienced with larger calorie deficits.

So, in our example case I would recommend he start with creating a calorie deficit of about 300 calories and set his daily calorie intake target at 2,000 calories.

This is enough for steady fat loss especially when combined with the proper macronutrient ratios, nutrient dense whole foods, and exercise program and will prevent excessive hunger and fatigue. 

Once you've calculated how many calories you need to consume each day for fat loss the next step is to calculate your macronutrient ratios which also consists of 3 steps.

Step 1: Determine Protein Intake

The U.S. Recommended Daily Allowance (RDA) for protein is 0.8 gram per kilogram (kg) of body weight per day or .36 grams per pound of body weight.

This amount is definitely on the lower end for protein intake and may be sufficient for average sized sedentary individuals but a better strategy for protein intake is to eat an amount of protein in grams that is closer to lean body mass since this will support your current lean body mass and prevent loss of lean mass as you create a calorie deficit.

People who are very active and participate regularly in high intensity exercise like playing sports and resistance training can also benefit from a higher intake as well. So, a better amount of protein intake is about 1 gram per pound of ideal/goal bodyweight.

Keeping with our example, if his goal bodyweight is 170 pounds we would simply set his protein intake target at 170 grams per day which is 680 calories because protein contains 4 calories per gram.

Then to ensure sufficient amino acids to support the connective tissues of the body, tendons, ligaments, fascia, hair, skin, etc. 10 to 20 percent of the 170 grams should be from collagen rich sources like bone broth or even a collagen supplement.

Step 2: Determine Fat Intake

Due to the metabolic process of The Randle Cycle, fat intake should be below 30 percent of total calorie intake to allow carbohydrates to be properly metabolized in the mitochondria and optimal mitochondrial energy production.

Therefore, I recommend setting fat intake to 25-28 percent of total calorie intake.

So our example this means we would set his initial fat intake target to 60 grams which is 540 calories since fat contains 9 calories per gram.

Step 3: Determine Carb Intake

Carb intake will simply make up the rest of the remaining calories needed to hit the total calorie intake target for fat loss.

Add the total protein and fat calorie targets and subtract from the total calorie intake target to determine carb intake. Then divide by 4 to determine grams.

To finish our example, we would take the 680 calories from protein and add them to the 540 calories from fat which equals 1,220 calories.

Then since his daily calorie intake goal is 2,000 we need to subtract 2,000 by 1,220 which gives us 780 calories or 195 grams of carbs.

If we wanted to figure out the percentage that each macronutrient accounts for we would simply divide each macronutrient target in calories by his 2,000-calorie intake goal.

In this case his protein intake makes up 34% of total calories, fat intake makes up 27% of total calories, and carbs makes up 39% of calories.

Now, once you have your calorie and macronutrient targets for fat loss that is just the start of this process! There are two essential practices to begin for this process to work:

1) Assess Your Body Composition Consistently- as I mentioned earlier the only type of weight you want to lose is fat while maintaining or increasing muscle mass, but unfortunately this is difficult to accurately measure and track because of the lack of accuracy of most methods of assessing body composition like home scales.

So you can simply get a regular scale and track your weight at least weekly. If you do want a scale that also measures body fat percentage and muscle mass, I recommend the Withings Body+ which is what I use with my clients since it syncs directly with The PHP Coaching App.

Just don't take the body fat percentage and muscle mass numbers for exact measures and don't assess the accuracy of your calories and macros based on those numbers alone, especially in the short term.

Then along with this take standing position photos of yourself every two to four weeks which will allow you to clearly see the changes in your body composition. Especially if your primary goal of all of this is to look leaner.

2) Start tracking your food intake- There are many different options to track your food. I personally have used My Fitness Pal and Nutritionix the most myself and with clients and they both get the job done. The most important thing is to get set with one tracker and get your most typical meals and foods added in so that you can easily enter in your food intake and track it each day.

It’s important to understand that tracking calories is not an exact process. According to FDA policies, some variation in the stated calorie count on labels is allowed and the calories in a packaged food product can differ from what is stated on the nutrition facts label by up to 20%.

Studies have also shown that restaurant nutrition information can be off by a few hundred calories.²¹ Cooking methods also can change how many calories a food contains.

Track your food intake as accurately as possible to hit your calorie and macro targets for a week, then reassess your weight to see if you gained weight, maintained, or lost weight.

If you lost weight, great stick with the targets you set.

If you maintained weight, decrease your calorie intake by 100 calories by decreasing your carb intake by 25 grams.

If you gained weight then decrease your calories by 200 calories by decreasing your carb intake by about 40 grams and decreasing your fat intake by about 10 grams.

Then see how these adjustments affect your weight over the next three to seven days and repeat this process.

Creating this feedback loop between your body composition and your intake targets is really where you can precisely dial in your calorie and macro targets and lose fat on demand.

The last thing you have to understand about tracking your calories and macros for fat loss is that this is a dynamic process because your body is a dynamic organism!

So as your body composition changes your metabolism changes, and you’ll most likely need to adjust your targets to avoid hitting plateaus. Again, keep assessing your body composition, tracking your intake as accurately as possible, and making the necessary adjustments.

Once you get the hang of this process of calculating and consuming your calorie and macronutrient targets that match your body composition goals you will have one of the most powerful skills for sustainably achieving your best body composition and physique.

If you want a coach to guide you step by step through this process and help you make the necessary adjustments along the way so you can achieve your fat loss goal with speed and sustainability then click on Contact above to request a free 6 Pack Strategy Session.

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References:

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