TDEE Calculator

Total Daily Energy Expenditure (TDEE) represents the absolute number of kilocalories a human body burns in a 24-hour period, encompassing basic life-sustaining functions, physical movement, and the digestion of food. Understanding this biological metric is the foundational requirement for any purposeful manipulation of human body composition, whether the goal is shedding adipose tissue, synthesizing new skeletal muscle, or maintaining current mass. By mastering the physiological components and mathematical formulas that dictate energy expenditure, individuals can replace dietary guesswork with precise, scientifically validated nutritional protocols.

What It Is and Why It Matters

Total Daily Energy Expenditure is the practical application of the First Law of Thermodynamics to human biology, dictating that energy can neither be created nor destroyed, only transferred or transformed. In the context of the human body, energy is consumed through food and beverages (measured in kilocalories) and expended through metabolic processes, voluntary movement, and involuntary physiological maintenance. When the energy consumed matches the energy expended, the body remains in a state of energy balance, maintaining its current mass. When consumption exceeds expenditure, the surplus energy is stored primarily as adipose tissue (fat) or synthesized into muscle tissue, resulting in weight gain. Conversely, when expenditure exceeds consumption, the body is forced to catabolize stored tissues to meet its energy demands, resulting in weight loss.

Understanding your TDEE is the single most critical data point in nutritional science because it provides the exact mathematical baseline required to manipulate body weight. Without an accurate estimate of daily energy expenditure, any attempt to diet or build muscle relies entirely on blind luck and subjective intuition. For a 15-year-old high school athlete trying to gain strength, a 45-year-old executive attempting to lose visceral fat, or a clinical dietitian formulating a feeding tube protocol, TDEE serves as the unalterable starting point. It solves the fundamental problem of nutritional uncertainty by translating complex metabolic biology into a single, actionable number. By establishing this baseline, individuals can engineer precise caloric deficits for fat loss or caloric surpluses for muscle hypertrophy, transforming body composition from a mystery into a predictable mathematical equation.

History and Origin

The scientific quest to quantify human energy expenditure began in earnest in the late 19th and early 20th centuries, driven by the need to understand human metabolism, agricultural requirements, and medical nutrition. The seminal breakthrough occurred in 1919 when James Arthur Harris and Francis Gano Benedict published "A Biometric Study of Basal Metabolism in Man" through the Carnegie Institution of Washington. Harris, a botanist and biometrician, and Benedict, a pioneering chemist, utilized a massive, sealed respiration calorimeter to precisely measure the oxygen consumption and carbon dioxide production of 136 men, 103 women, and 94 infants. By analyzing this gas exchange, they established the first universally adopted mathematical model predicting Basal Metabolic Rate (BMR) based on an individual's weight, height, age, and sex.

For over seventy years, the Harris-Benedict equation remained the undisputed gold standard in clinical and athletic settings. However, as the 20th century progressed, the average human body composition shifted drastically due to changes in diet, lifestyle, and the onset of the global obesity epidemic. Recognizing that the original 1919 formula was increasingly overestimating caloric needs in modern, less active populations, researchers Mark Mifflin and Sachiko St. Jeor published a newly calibrated equation in 1990. Conducted at the University of Nevada, the Mifflin-St Jeor study analyzed a diverse cohort of 498 normal-weight, overweight, and obese individuals. Their resulting equation proved significantly more accurate for the modern biological profile, reducing the margin of error from roughly 15% to within 10% of true resting metabolic rate. Subsequent developments by researchers like Frank Katch and William McArdle further evolved the science by shifting the focus from total body weight to lean body mass, acknowledging that muscle tissue is inherently more metabolically demanding than adipose tissue.

Key Concepts and Terminology

To accurately calculate and utilize Total Daily Energy Expenditure, one must first understand the four distinct physiological components that comprise it. The largest component is the Basal Metabolic Rate (BMR), which accounts for roughly 60% to 70% of total daily energy expenditure in the average human. BMR represents the absolute minimum number of calories required to keep the body alive at complete rest, funding vital functions such as cardiovascular pumping, neurological activity, pulmonary respiration, and cellular regeneration. Closely related but distinct is Resting Metabolic Rate (RMR), which includes BMR plus the minimal energy required for minor daily movements like sitting upright or eating; however, the two terms are frequently used interchangeably in practical settings.

The second component is Non-Exercise Activity Thermogenesis (NEAT), which accounts for 15% to 20% of TDEE. NEAT encompasses all the calories burned through subconscious, non-athletic movements, including fidgeting, maintaining posture, typing, pacing, and basic occupational tasks. NEAT is highly variable between individuals and is the primary mechanism by which the body subconsciously defends against weight loss or gain. The third component is the Thermic Effect of Food (TEF), comprising roughly 10% of TDEE. TEF represents the energy required to masticate, digest, absorb, and store the macronutrients consumed in the diet. Protein has the highest thermic effect (burning 20-30% of its calories during digestion), followed by carbohydrates (5-10%), and fats (0-3%). Finally, the Thermic Effect of Activity (TEA), also known as Exercise Activity Thermogenesis (EAT), represents the calories burned during intentional, structured physical exercise. For most non-athletes, TEA accounts for a surprisingly small portion of TDEE, typically only 5% to 10%, highlighting why diet and baseline movement are vastly more influential for weight management than brief periods of intense gym activity.

How It Works — Step by Step

Calculating Total Daily Energy Expenditure is a two-step mathematical process: first, determining the Basal Metabolic Rate (BMR) using a validated physiological equation, and second, multiplying that BMR by an activity factor that accounts for NEAT and TEA. The most widely accepted formula for modern populations is the Mifflin-St Jeor equation. The formula relies on three specific biological variables: Weight ($W$) measured in kilograms, Height ($H$) measured in centimeters, and Age ($A$) measured in years. The equation separates by biological sex to account for the average differences in lean muscle mass between males and females.

The Mathematical Formulas

For Males, the BMR formula is: $BMR = (10 \times W) + (6.25 \times H) - (5 \times A) + 5$ For Females, the BMR formula is: $BMR = (10 \times W) + (6.25 \times H) - (5 \times A) - 161$

Once the BMR is established, the result is multiplied by an Activity Multiplier. These standard multipliers range from 1.2 for sedentary individuals to 1.9 for elite athletes undergoing extreme daily training.

A Full Worked Example

Consider a hypothetical subject: John is a 35-year-old male who weighs 85 kilograms (approximately 187 pounds) and stands 180 centimeters tall (approximately 5 feet 11 inches). John works a desk job but goes for a light 30-minute walk three times a week, placing him in the "Lightly Active" category with a multiplier of 1.375.

Step 1: Calculate John's Weight Component: $10 \times 85 = 850$ Step 2: Calculate John's Height Component: $6.25 \times 180 = 1,125$ Step 3: Calculate John's Age Component: $5 \times 35 = 175$ Step 4: Combine the components using the male formula: $850 + 1,125 - 175 + 5 = 1,805$ John's Basal Metabolic Rate is 1,805 kilocalories per day. This is the energy he would burn if he remained comatose in bed for 24 hours.

Step 5: Apply the Activity Multiplier to find TDEE. $1,805 \times 1.375 = 2,481.87$ Therefore, John's Total Daily Energy Expenditure is approximately 2,482 kilocalories. To maintain his current weight of 85 kilograms, John must consume exactly 2,482 calories per day. If he wishes to lose roughly one pound of fat per week, he would subtract 500 calories, establishing a daily target of 1,982 calories.

Types, Variations, and Methods

While the overarching concept of TDEE remains consistent, the mathematical models used to estimate the foundational Basal Metabolic Rate vary based on the specific population being assessed and the data available. The four primary formulas utilized in nutritional science each carry distinct advantages, trade-offs, and optimal use cases. Understanding which formula to apply is critical for generating an accurate caloric baseline.

The Mifflin-St Jeor Equation is the current clinical standard for the general population. Because it was developed in 1990, it accurately reflects the body composition and metabolic realities of modern individuals, making it highly reliable for normal-weight, overweight, and moderately obese subjects. However, because it relies strictly on total body weight rather than distinguishing between fat and muscle, it can underestimate the caloric needs of highly muscular bodybuilders and overestimate the needs of the clinically obese.

The Harris-Benedict Equation (specifically the 1984 Roza-Shizgal revision) remains widely used but is generally considered outdated for modern populations. Because the original 1919 subjects were significantly more active and possessed different baseline body compositions than today's average citizen, Harris-Benedict tends to overestimate BMR by 5% to 10%. It is generally avoided by modern dietitians unless dealing with extremely active, lean populations that mimic early 20th-century physical baselines.

The Katch-McArdle Equation represents a paradigm shift because it abandons biological sex, height, and age entirely, relying solely on Lean Body Mass (LBM). The formula is: $BMR = 370 + (21.6 \times LBM \text{ in kg})$. This equation is universally considered the most accurate method for athletic populations, bodybuilders, and those with atypical body compositions. However, its fatal flaw is that it requires an accurate measurement of body fat percentage (via DEXA scan or hydrostatic weighing) to calculate Lean Body Mass. If a subject guesses their body fat percentage incorrectly, the resulting TDEE calculation will be wildly inaccurate.

The Cunningham Equation is a slight variation of Katch-McArdle, formulated as $BMR = 500 + (22 \times LBM \text{ in kg})$. Developed specifically to predict the resting metabolic rate of elite endurance athletes and professional competitors, it assumes a higher baseline of metabolic activity in the muscle tissue of highly trained individuals. It is exclusively reserved for the upper echelon of athletic performers and will severely overestimate the caloric needs of recreational gym-goers.

Industry Standards and Benchmarks

In the fields of clinical dietetics, sports nutrition, and professional bodybuilding, practitioners rely on standardized benchmarks to categorize physical activity and prescribe caloric adjustments. The bedrock of these standards is the Katch-McArdle Activity Multiplier scale, which categorizes human movement into five distinct tiers.

Standard Activity Multipliers

1. Sedentary (Multiplier: 1.2): Represents an individual with a desk job who engages in little to no structured exercise. Their daily step count is typically below 5,000.
2. Lightly Active (Multiplier: 1.375): Represents an individual who exercises lightly 1 to 3 days per week, or someone with a job that requires prolonged standing, such as a teacher or retail worker.
3. Moderately Active (Multiplier: 1.55): Represents an individual who engages in moderate-intensity exercise 3 to 5 days per week, achieving elevated heart rates for 45-60 minutes per session.
4. Very Active (Multiplier: 1.725): Represents an individual who engages in hard exercise 6 to 7 days per week, or someone working a highly physical job, such as a roofer, construction worker, or agricultural laborer.
5. Extra Active (Multiplier: 1.9): Exclusively reserved for elite athletes undergoing multiple training sessions per day, or extreme endurance competitors like marathon runners and triathletes.

Caloric Manipulation Standards

When adjusting TDEE for body composition changes, the industry standard for weight loss is the "500-Calorie Rule." Because one pound of human adipose tissue contains approximately 3,500 kilocalories of stored energy, creating a daily deficit of 500 calories ($500 \times 7 \text{ days}$) yields a theoretical fat loss of one pound per week. While metabolic adaptation makes this non-linear over long periods, it remains the universally accepted starting point. For muscle hypertrophy (bulking), the standard benchmark is much more conservative. Because the physiological synthesis of new muscle tissue is chemically expensive but biologically slow, experts recommend a surplus of only 200 to 300 calories above TDEE. Surpluses exceeding 500 calories rarely result in faster muscle growth; instead, the excess energy spills over into adipose tissue storage.

Real-World Examples and Applications

To understand how TDEE dictates nutritional protocols, we must examine concrete, real-world scenarios across drastically different human profiles. Theoretical math only becomes valuable when applied to specific physiological goals and daily routines.

Scenario 1: The Sedentary Office Worker Seeking Fat Loss Sarah is a 28-year-old female software developer. She weighs 165 pounds (75 kg), stands 5 feet 4 inches (162.5 cm), and works remotely. She averages 3,000 steps per day and does not go to the gym. Using the Mifflin-St Jeor equation, her BMR is calculated at 1,489 calories. Because she is completely sedentary, we apply the 1.2 multiplier. Sarah's maintenance TDEE is 1,787 calories per day. To achieve a healthy weight loss of one pound per week, she requires a 500-calorie deficit. Therefore, her daily target becomes 1,287 calories. Because this number borders on the clinical minimum for female nutritional adequacy (1,200 calories), a professional dietitian would likely advise Sarah to increase her daily step count to 8,000 (raising her multiplier to 1.375 and her TDEE to 2,047). This behavioral change allows her to eat 1,547 calories while still losing a pound per week, significantly improving dietary adherence and micronutrient intake.

Scenario 2: The Physical Laborer Seeking Muscle Gain David is a 24-year-old male commercial landscaper. He weighs 155 pounds (70.3 kg), stands 5 feet 10 inches (177.8 cm), and performs manual labor in the sun for eight hours a day. He also lifts weights four evenings a week with the goal of gaining muscle mass. His BMR is 1,676 calories. Due to his grueling occupational demands combined with weightlifting, he falls into the "Very Active" category, requiring a 1.725 multiplier. David's maintenance TDEE is a staggering 2,891 calories. To build muscle at an optimal rate without gaining excessive fat, he requires a 300-calorie surplus. David's daily target becomes 3,191 calories. If David attempts to build muscle by eating a standard "healthy" diet of 2,200 calories, he will remain in a severe 691-calorie deficit, resulting in weight loss, muscle catabolism, and severe fatigue, entirely sabotaging his goals despite his intense gym efforts.

Common Mistakes and Misconceptions

The mathematical simplicity of energy expenditure often masks the behavioral complexities of applying it, leading to widespread errors among novices and intermediate practitioners alike. The single most pervasive mistake is the drastic overestimation of physical activity levels. Human psychology inherently biases individuals to view their physical exertion as more significant than it biologically is. A person who sits at a desk for 23 hours a day but spends 45 minutes walking on a treadmill will frequently categorize themselves as "Moderately Active" (1.55 multiplier). In reality, 45 minutes of walking burns roughly 200 calories, while the 1.55 multiplier adds over 600 calories to their BMR. This single psychological error wipes out their intended caloric deficit, leading to the common lament that "the math doesn't work for my body."

A second major misconception is the belief in "Starvation Mode," a heavily misunderstood interpretation of adaptive thermogenesis. Many beginners believe that if they cut their calories too low beneath their TDEE, their metabolism will instantly halt, and they will begin gaining fat out of thin air. This violates the laws of thermodynamics. While severe caloric restriction does cause the body to downregulate BMR and subconsciously reduce NEAT (a process called metabolic adaptation), this reduction rarely exceeds 10% to 15% of total expenditure. The body never stops burning calories, and starvation never causes weight gain; the cessation of weight loss is almost always due to the dieter unknowingly breaking their deficit through untracked bites, licks, and tastes, or drastically reducing their subconscious daily movement due to low energy.

Finally, individuals frequently fail to treat TDEE as a dynamic, moving target. TDEE is heavily dependent on total body mass. If an obese individual weighing 250 pounds calculates their TDEE at 2,800 calories and successfully diets down to 210 pounds over six months, their new, lighter body requires significantly less energy to exist and move through space. Their new TDEE might be 2,400 calories. If they continue eating the 2,300 calories that previously generated a rapid deficit, they will suddenly hit a plateau, as their old "weight loss calories" have now become their new maintenance calories. Failing to recalculate TDEE for every 10 pounds of weight loss is the primary cause of dietary plateaus.

Best Practices and Expert Strategies

Professional nutritionists, elite physique coaches, and registered dietitians do not view a calculated TDEE as absolute truth; rather, they view it as an educated hypothesis that must be tested and refined against real-world biological feedback. The expert strategy begins with the "Two-Week Baseline Phase." Instead of immediately plunging into a deficit or surplus, the practitioner calculates the estimated TDEE and instructs the subject to consume exactly that number of calories for 14 consecutive days. During this period, the subject weighs themselves every single morning after using the restroom but before consuming food or water.

Because daily body weight fluctuates wildly due to sodium intake, carbohydrate storage, hydration status, and intestinal residue, experts completely ignore daily scale readings. Instead, they calculate the 7-day average weight for Week 1 and compare it to the 7-day average weight for Week 2. If the average weight remains perfectly static, the calculated TDEE is 100% accurate. If the average weight drops by 0.5 pounds, the subject was actually in a slight deficit, meaning their true TDEE is roughly 250 calories higher than the mathematical formula predicted. This bio-feedback loop allows the practitioner to calibrate the formula to the specific metabolic idiosyncrasies of the individual.

Furthermore, experts strategically manipulate the macronutrient composition of the TDEE to maximize metabolic advantages. Because the Thermic Effect of Food (TEF) for protein is 20% to 30%, prescribing a high-protein diet (typically 1 gram per pound of target body weight) effectively increases the subject's total daily energy expenditure. A 2,000-calorie diet consisting of 40% protein will result in more net calories burned during digestion than a 2,000-calorie diet consisting of 10% protein. This "metabolic advantage" of high-protein diets, combined with protein's high satiety index, makes adherence to the TDEE target significantly easier for the client, transforming a difficult mathematical restriction into a manageable lifestyle protocol.

Edge Cases, Limitations, and Pitfalls

While standard energy expenditure formulas are remarkably accurate for 85% of the population, they break down when applied to specific physiological edge cases. The most prominent limitation involves clinical endocrine disorders, specifically hypothyroidism and Polycystic Ovary Syndrome (PCOS). In a healthy individual, the thyroid gland produces hormones (T3 and T4) that regulate the cellular metabolic rate. In subjects with untreated hypothyroidism, this hormonal signaling is blunted, which can depress the Basal Metabolic Rate by 10% to 15%. For a woman with a calculated TDEE of 1,800 calories, an untreated thyroid condition might lower her actual expenditure to 1,550 calories, making standard deficit protocols highly frustrating and seemingly ineffective until medical intervention corrects the hormonal baseline.

Extreme obesity presents another significant pitfall for standard calculations. Because adipose (fat) tissue is relatively inert and requires very little energy to sustain compared to muscle tissue or internal organs, applying the Mifflin-St Jeor equation to an individual who weighs 400 pounds with 50% body fat will result in a dramatically overestimated BMR. The formula assumes a standard ratio of fat-to-muscle mass; when this ratio is severely skewed by massive adiposity, the math fails. In clinical settings, dietitians bypass this by using an "Adjusted Body Weight" formula, which calculates the subject's ideal body weight and adds a 25% to 50% buffer to account for the excess metabolically active tissue required to carry the extra fat, yielding a much safer and more accurate caloric target.

Conversely, individuals with extraordinary amounts of lean muscle mass—such as professional bodybuilders or elite powerlifters—will find standard formulas severely underestimate their needs. Muscle tissue is metabolically "expensive," burning roughly 6 calories per pound per day at rest, compared to fat's 2 calories per pound. A 220-pound bodybuilder at 8% body fat possesses vastly more muscle than a 220-pound sedentary individual at 30% body fat. If both use the Mifflin-St Jeor equation, they will receive the exact same TDEE, completely ignoring the bodybuilder's roaring metabolic engine. In these edge cases, the Katch-McArdle equation, which relies entirely on lean body mass, becomes mandatory to prevent severe underfeeding and muscle catabolism.

Comparisons with Alternatives

The mathematical calculation of TDEE is not the only method utilized to determine energy expenditure. In recent years, Wearable Fitness Trackers (such as the Apple Watch, Fitbit, and Garmin devices) have become ubiquitous alternatives. These devices use photoplethysmography (optical heart rate monitoring) and multi-axis accelerometers to estimate daily caloric burn in real-time. While convenient, clinical studies consistently demonstrate that commercial wearables overestimate energy expenditure by anywhere from 15% to 40%, particularly during low-intensity tasks like walking or household chores. Relying on a smartwatch to determine your daily caloric intake is a massive pitfall; individuals who "eat back" the calories their watch claims they burned almost universally fail to lose weight due to the device's inherent margin of error. TDEE formulas, while static, provide a far more reliable baseline for nutritional planning.

Another alternative is Intuitive Eating, a paradigm that discards caloric tracking entirely in favor of listening to internal hunger and satiety cues. While Intuitive Eating is highly effective for psychological healing from eating disorders and maintaining a stable weight in a healthy food environment, it is drastically inferior to calculated TDEE for purposeful body composition changes. The modern food environment is engineered with hyper-palatable, calorie-dense foods designed to override natural satiety signals. Expecting an individual to intuitively eat their way into a precise 500-calorie deficit while surrounded by processed foods is mathematically improbable. TDEE calculations provide objective, unemotional data, whereas intuition is easily manipulated by cravings, stress, and sleep deprivation.

The gold standard alternative to predictive formulas is Direct Calorimetry, typically conducted in a metabolic ward. In this scenario, a subject is placed inside a sealed, temperature-controlled room for 24 hours while scientists measure the exact amount of heat their body radiates and the precise gas exchange of their respiration. While this method provides a 100% accurate measurement of energy expenditure, it costs tens of thousands of dollars, requires clinical confinement, and is exclusively reserved for high-level scientific research. For 99.9% of the human population, the predictive mathematical formulas of a TDEE calculation offer the perfect intersection of zero-cost accessibility and high-level practical accuracy.

Frequently Asked Questions

Does my TDEE change from day to day? Yes, your actual energy expenditure fluctuates daily based on your Non-Exercise Activity Thermogenesis (NEAT) and your Thermic Effect of Activity (TEA). If you spend Saturday hiking for four hours and Sunday lying on the couch watching television, your absolute caloric burn on Saturday will be significantly higher than on Sunday. However, attempting to micro-manage your diet by eating different caloric amounts every single day based on minor activity fluctuations is psychologically exhausting and prone to tracking errors. This is why professionals use an Activity Multiplier to establish a smoothed-out, average daily TDEE, allowing you to consume a consistent number of calories seven days a week while achieving the same net weekly energy balance.

Should I eat back the calories I burn from exercise? No, you should almost never add exercise calories back into your daily nutritional targets. When you calculate your TDEE using an Activity Multiplier (such as 1.55 for moderate exercise), the calories burned during your workouts have already been factored into the final mathematical result. If your calculated TDEE is 2,500 calories, that number already assumes you are going to the gym. If you go to the gym, burn 400 calories, and then eat an extra 400 calories on top of your TDEE target, you are "double-dipping" and effectively erasing the caloric deficit required for weight loss. The only exception is for endurance athletes completing highly anomalous, multi-hour training events (like running a marathon) that fall drastically outside their standard weekly routine.

How do macronutrients affect my calculated TDEE? While your total caloric target determines whether you gain or lose weight, your macronutrient split (the ratio of protein, carbohydrates, and fats) dictates the composition of that weight change. Protein is the most critical macronutrient because it carries a high Thermic Effect of Food (TEF), meaning your body burns up to 30% of the calories from protein simply digesting it. Furthermore, adequate protein intake (roughly 0.8 to 1 gram per pound of body weight) ensures that during a caloric deficit, the body burns adipose tissue rather than catabolizing skeletal muscle. Carbohydrates serve as the primary fuel source for high-intensity exercise, while dietary fats are essential for hormonal regulation and cellular health.

Why is my calculated TDEE not resulting in weight loss? If you have calculated your TDEE, subtracted 500 calories, adhered to the diet for three weeks, and have not lost weight, the laws of thermodynamics have not failed; rather, there is an error in your data input. The most common culprit is underestimating caloric intake through inaccurate portion sizing. Without using a digital kitchen scale to weigh food in grams, humans consistently underestimate their consumption by 20% to 30%. Liquid calories, cooking oils, and untracked condiments easily close a 500-calorie deficit. Alternatively, you may have overestimated your Activity Multiplier, calculating your BMR against a "Highly Active" lifestyle when your daily reality is largely sedentary. You must lower your caloric target or increase your daily step count to force the deficit.

Does age significantly slow down my daily energy expenditure? Age does decrease Basal Metabolic Rate, but the physiological slowdown is vastly overstated in popular culture. The Mifflin-St Jeor equation accounts for this by subtracting 5 calories for every year of age. Therefore, the metabolic difference between a 25-year-old and a 45-year-old of the exact same weight and height is only 100 calories per day—roughly the equivalent of one apple. The primary reason older individuals experience weight gain is not a crashing metabolism, but a drastic reduction in Non-Exercise Activity Thermogenesis (NEAT) and a gradual loss of metabolically active muscle tissue (sarcopenia) due to increasingly sedentary lifestyles. Maintaining resistance training and high daily step counts largely negates the age-related decline in TDEE.

How does muscle mass impact my daily energy expenditure? Skeletal muscle is highly metabolically active tissue, requiring constant energy to maintain its cellular structure, repair micro-tears, and store glycogen. One pound of muscle at rest burns approximately 6 kilocalories per day, whereas one pound of adipose tissue (fat) burns roughly 2 kilocalories per day. While an extra 4 calories per pound may seem insignificant, gaining 10 pounds of muscle permanently increases your Basal Metabolic Rate by roughly 60 calories per day, every day, regardless of activity. More importantly, moving a heavily muscled body through space during physical activity requires significantly more energy than moving a lighter frame. Building muscle is the single most effective permanent strategy for increasing your Total Daily Energy Expenditure and expanding your daily caloric allowance.