Understanding the Science: Why Do Girls Burn Less Calories?

November 2, 2025 •

4 min read

On average, a woman's basal metabolic rate (BMR) is 5 to 10 percent lower than a man's, meaning they burn fewer calories at rest. This significant difference answers the question: why do girls burn less calories?—and it primarily comes down to fundamental variations in body composition and hormonal profiles, rather than physical effort.

Quick Summary

This article explores the physiological distinctions between male and female metabolism, focusing on the higher body fat and lower muscle mass in females. It details how hormonal factors, life stages like pregnancy and menopause, and metabolic adaptations contribute to differences in energy expenditure and calorie burn.

Key Points

Body Composition: On average, females have a higher percentage of body fat and less muscle mass than males, which is the primary reason for a lower basal metabolic rate.
Metabolic Muscle vs. Fat: Muscle tissue burns more calories at rest than fat tissue, contributing to men's higher overall calorie expenditure.
Hormonal Influence: Estrogen and progesterone play a significant role in fat distribution and metabolism, and their fluctuations during the menstrual cycle and menopause can impact calorie burn.
Evolutionary Adaptation: The tendency for women to have more body fat is partly an evolutionary trait linked to childbearing, allowing for energy storage.
Basal Metabolic Rate (BMR): Due to body composition, women typically have a lower BMR than men, meaning their bodies burn fewer calories for basic bodily functions.
Effective Strategy: For women, prioritizing resistance training to build muscle mass is a key strategy for boosting their metabolic rate and supporting weight management goals.
Personalized Approach: Due to these biological differences, an individualized approach to diet and exercise is more effective than comparing progress to men's or following one-size-fits-all advice.

For many years, the discrepancy in how men and women burn calories has been observed, with men typically demonstrating a higher rate of expenditure. While lifestyle and activity level play a significant role, the underlying physiological differences in body composition and hormones are the primary determinants. Understanding these distinctions is crucial for women aiming to manage their weight and nutritional needs effectively.

The Core Reason: Body Composition

The most significant factor explaining why girls burn less calories is their body composition. On average, females naturally have a higher percentage of body fat and a lower percentage of muscle mass compared to males. This is not a matter of fitness level, but a fundamental biological difference.

Muscle vs. Fat: A Metabolic Difference

Muscle tissue is more metabolically active than fat tissue, meaning it burns more calories to sustain itself, even while at rest. In contrast, fat tissue is less active and requires fewer calories for maintenance. Since males, on average, possess a greater lean muscle mass, their resting metabolic rate is higher. This inherent difference in muscle-to-fat ratio is a key reason for the lower basal metabolic rate (BMR) observed in females.

Muscle is a calorie-burning engine: More muscle mass translates to more calories burned throughout the day, regardless of activity level.
Fat is an energy-storing organ: Evolutionarily, the higher percentage of body fat in females serves as an energy reserve, particularly important for reproduction and pregnancy.

The Hormonal Influence on Female Metabolism

Fluctuating hormones are another powerful contributor to metabolic differences and influence how females store fat and burn calories. The primary female sex hormones, estrogen and progesterone, play a direct role in regulating metabolism and appetite.

The Role of Estrogen and Progesterone

Estrogen, in particular, affects the distribution of body fat and influences how efficiently the body burns calories. During the menstrual cycle, hormonal shifts can lead to changes in appetite and calorie burn. A study cited by Levels indicates that women burn fewer calories during the follicular phase compared to the luteal phase. During menopause, as estrogen levels decline, many women experience a slower metabolism and an increase in abdominal fat storage.

Other Hormonal Factors

Conditions such as Polycystic Ovary Syndrome (PCOS), which is much more common in women, involve hormonal imbalances that can make weight loss more difficult and contribute to insulin resistance. Stress hormones, like cortisol, can also promote fat storage, especially around the abdomen. Managing these hormonal factors is a critical part of a woman's weight management strategy.

The Basal Metabolic Rate (BMR) Discrepancy

The basal metabolic rate is the number of calories your body needs to perform basic life-sustaining functions at rest, such as breathing, circulation, and cell repair. A lower BMR is the direct result of the body composition and hormonal differences already discussed. It means that, for two individuals of the same age and weight, the female will almost always have a lower BMR. This is a fundamental reason why women typically need to consume fewer calories than men to maintain or lose weight.

How Body Size Affects Calorie Burn

Body size also affects total calorie expenditure. Since men are, on average, larger than women, they have more total mass and larger organs, which require more energy to operate. A study found that differences in organ size account for a significant portion of the variation in total calorie burn between individuals. This is another physiological aspect that contributes to the overall lower calorie burn for girls.

Practical Considerations for Women and Calorie Burn

Recognizing these biological differences is the first step toward a more effective and sustainable nutritional and fitness plan. Instead of comparing their progress to men's, women should focus on strategies that optimize their specific physiology.

Optimizing Your Calorie Burn

Prioritize resistance training: Building muscle is one of the most effective ways to increase BMR. Regular strength training can help increase lean muscle mass and counteract the natural metabolic slowdown that occurs with age.
Focus on high-protein nutrition: Protein is essential for building and maintaining muscle mass. A diet rich in lean protein can support muscle growth and help manage appetite.
Manage hormonal fluctuations: For women, being mindful of their menstrual cycle or menopausal stage can help adjust nutritional strategies. For example, paying closer attention to portion control during the luteal phase may be beneficial.

Comparison Table: Male vs. Female Calorie Burn Factors


Factor	Male (Average)	Female (Average)
Body Composition	Higher lean muscle mass, lower body fat percentage.	Lower lean muscle mass, higher body fat percentage.
Basal Metabolic Rate (BMR)	Higher due to greater muscle mass.	Lower due to less muscle mass.
Hormonal Influence	High testosterone levels support muscle growth.	Fluctuating estrogen and progesterone affect fat storage and appetite.
Fat Distribution	Tends to be stored around the abdomen ('apple-shaped').	Tends to be stored around the hips and thighs ('pear-shaped').
Weight Loss Rate	Often lose weight more quickly initially due to higher BMR.	May lose weight more slowly, but progress evens out over time with consistency.

Conclusion: Tailoring Your Approach

In conclusion, the answer to why do girls burn less calories? lies in a combination of innate physiological factors, including body composition and hormonal differences. It is not a sign of a flaw, but an evolutionary design that has served women throughout history. Rather than feeling discouraged by these metabolic realities, women should embrace them by focusing on personalized, sustainable strategies that work with their body, not against it. Prioritizing a balanced diet, including strength training, and managing hormonal health are all key components to a successful and healthy approach to weight management.

It is important to remember that slow and steady weight loss is often more sustainable than rapid weight loss. For individuals seeking more personalized guidance, consulting a healthcare professional or registered dietitian is always recommended.

Frequently Asked Questions

Yes, muscle tissue is more metabolically active than fat tissue. This means that a body with a higher percentage of lean muscle mass will burn more calories at rest, and during exercise, than a body with more fat and less muscle.

Hormones like estrogen and progesterone can influence metabolism, appetite, and fat storage in women. Fluctuations during the menstrual cycle, as well as changes during menopause, can impact calorie burn and make weight management more challenging.

Men often experience faster initial weight loss than women, largely due to having a higher metabolic rate from greater muscle mass. However, studies show that over time, the total amount of weight loss typically evens out between genders.

Yes, women can increase their metabolic rate by building and maintaining lean muscle mass through regular strength or resistance training. This helps increase the number of calories the body burns at rest.

BMR is the number of calories your body burns to perform basic functions while at rest. On average, men have a higher BMR than women, primarily due to having more muscle mass.

Because women generally have a lower basal metabolic rate than men, they require fewer calories to maintain or lose weight. This is due to natural differences in average body size and body composition.

Pregnancy causes metabolic and hormonal shifts, and some women may retain extra weight long-term. However, a woman's metabolism can be managed through diet, exercise, and a healthy lifestyle to support overall weight management post-pregnancy.