Understanding Why Do Men Require More Calories

December 30, 2025 •

4 min read

According to the National Institutes of Health, on average, men typically have a higher basal metabolic rate (BMR) than women, which directly contributes to why do men require more calories. The core differences lie in fundamental biological and hormonal distinctions that influence energy expenditure and storage.

Quick Summary

Men generally need more calories than women due to higher muscle mass, larger average body size, and greater levels of testosterone. These physiological factors increase a man's basal metabolic rate and overall daily energy expenditure, influencing caloric needs.

Key Points

Higher Muscle Mass: Men have more lean muscle tissue, which is metabolically more active and requires more calories to maintain, even at rest.
Larger Average Size: On average, men are taller and heavier, so their bodies need more energy to perform basic functions and to move.
Hormonal Influence: Testosterone promotes higher muscle mass and metabolic rate, contributing to greater caloric needs in men.
Evolutionary Specialization: Historically, female metabolism evolved to store fat more efficiently for reproductive purposes, while male metabolism prioritized energy for muscle-intensive activities.
Impact on BMR: The combination of these factors results in a higher basal metabolic rate (BMR) for men compared to women of a similar age and activity level.
Fat Distribution Differences: Men typically have more metabolically active visceral fat, while women have more subcutaneous fat, also affecting energy use.

The Core Differences in Body Composition

One of the most significant factors influencing caloric needs is body composition. On average, adult men have a greater percentage of lean muscle mass and a lower percentage of body fat compared to women. Muscle tissue is far more metabolically active than fat tissue, meaning it burns more energy even when the body is at rest. A person with more muscle mass will naturally have a higher resting metabolic rate, requiring more calories just to maintain their body weight. Conversely, having a higher body fat percentage means a lower resting metabolic rate, as fat tissue does not require as much energy to sustain.

The Impact of Size and Weight

Beyond just muscle mass, the average man tends to be larger and heavier than the average woman. It takes more energy to fuel a larger body and to carry that additional weight throughout the day. A larger body has more cells and requires more calories to power fundamental functions like breathing, circulation, and temperature regulation. Therefore, even if a man and a woman have the same activity level, the larger and heavier man will have a greater overall energy expenditure.

Hormonal and Evolutionary Factors

Hormones play a pivotal role in metabolic differences between the sexes. Testosterone, the primary male sex hormone, promotes muscle growth and increases overall metabolic rate. In contrast, estrogen, the primary female sex hormone, is linked to a more efficient fat-storing metabolism, a trait that evolved to support potential childbearing and lactation. These hormonal differences not only dictate body composition but also influence how the body utilizes and partitions energy.

From an evolutionary perspective, this metabolic distinction served a purpose. Females developed a metabolism designed to conserve energy and store fat, a survival mechanism to ensure the continuation of the species during periods of food scarcity. Males evolved a metabolism that favors mobilizing energy stores for intense, short-term activity, which was beneficial for hunting and competition.

Metabolic Substrate Utilization

Research indicates that men and women also differ in how they metabolize fuel sources. During exercise, women tend to oxidize a higher proportion of fat relative to carbohydrates, while men preferentially use carbohydrates. This means that while women may be more efficient at using fat for fuel during moderate exercise, men's higher overall muscle mass and different hormonal profiles drive a greater overall daily energy burn that requires more total calories to sustain.

Calorie Needs and Activity Level

Activity level is a major determinant of daily caloric needs for both men and women, but the baseline differences in BMR and body composition mean that men typically burn more calories for the same activity. A very active woman may still require more calories than a sedentary man, but when comparing individuals with similar activity levels, the gender-based physiological differences hold true.

For example, a man and a woman of the same weight might complete the same workout. However, because of his higher muscle-to-fat ratio, the man will likely burn more calories during that workout and continue to have a higher metabolic rate during recovery. This dynamic explains why, in some weight loss studies, men lose weight faster than women when following the same diet.

The Role of Age

Both men and women experience a decline in metabolic rate as they age, primarily due to a natural loss of muscle mass. However, the gender-based differences in metabolism and body composition persist throughout the lifespan. As people get older, it becomes even more critical to focus on strength training and maintaining muscle mass to help mitigate this age-related metabolic slowdown.

Comparison of Calorie-Influencing Factors

To summarize the key physiological differences, here is a comparison table:


Factor	Men	Women
Average Body Size	Generally taller and heavier	Generally shorter and lighter
Body Composition	Higher percentage of lean muscle mass; lower percentage of body fat	Higher percentage of body fat; lower percentage of lean muscle mass
Resting Metabolic Rate (BMR)	Higher on average, even at rest	Lower on average, even at rest
Primary Hormones	Higher testosterone, which promotes muscle growth	Higher estrogen, which promotes fat storage efficiency
Fat Distribution	More visceral fat (stored around organs)	More subcutaneous fat (stored under the skin)
Fuel Use During Exercise	Tends to use more carbohydrates	Tends to use more fat

How Caloric Needs Are Estimated

Caloric needs are typically estimated using formulas that take into account an individual's age, sex, weight, height, and activity level. These equations, such as the Mifflin-St Jeor equation, have distinct calculations for men and women to account for their biological differences. For example, the formulas incorporate a higher basal metabolic rate for men. These aren't just arbitrary numbers; they are derived from decades of scientific observation and data that confirm the distinct energetic needs of the two sexes.

Conclusion

The reason why men require more calories than women is not a matter of a simple one-to-one comparison but the result of a complex interplay of physiology. From greater muscle mass and larger average body size to fundamental hormonal differences and evolutionary strategies, these biological factors create a measurable disparity in daily energy requirements. While generalizations exist, individual needs vary, and factors like age and activity level can significantly alter one's caloric expenditure. For anyone seeking to understand their personal nutritional requirements, taking these gender-based distinctions into account is a crucial step toward achieving optimal health and wellness.

For further reading on estimated dietary energy requirements based on sex and age, you can consult authoritative resources like the National Center for Biotechnology Information (NCBI) on the National Institutes of Health website. https://www.ncbi.nlm.nih.gov/sites/books/NBK234938/

Frequently Asked Questions

Yes, on average, men have a faster metabolism than women. This is largely due to men possessing more lean muscle mass, which is more metabolically active than the fat tissue that women tend to carry more of.

Caloric needs vary significantly based on age, size, and activity level. However, for a moderately active lifestyle, the National Health Service suggests an average man needs 2,500 kcal per day, while an average woman needs 2,000 kcal.

Yes, it can. Because of a higher baseline metabolic rate and greater muscle mass, men often experience faster initial weight loss when compared to women following a similar caloric-deficit diet and exercise plan.

Larger body size is a key contributor, as it requires more energy to function. However, it is not the sole reason. The greater proportion of metabolically active muscle mass is an equally, if not more, significant factor.

Hormones like testosterone in men promote muscle mass and elevate metabolism, while estrogen in women contributes to a higher body fat percentage and more efficient fat storage, leading to lower overall caloric needs.

Not necessarily. Even at the same weight, a man typically has a higher muscle-to-fat ratio than a woman. This means his metabolic rate will be higher, and he will require more calories to maintain that weight.

Yes, studies show that during exercise, women tend to use a higher proportion of fat as fuel, while men typically rely more on carbohydrates. This is another example of a sex-specific metabolic difference.