Why do boys need to eat more than girls? The scientific reasons

November 2, 2025 •

4 min read

Research observing food intake during puberty reveals that adolescent males consistently consume significantly more energy than females across all stages. This article explains the scientific reasons why do boys need to eat more than girls, examining biological and hormonal factors that drive their differing appetites and growth patterns.

Quick Summary

Boys' higher calorie needs are primarily driven by greater lean muscle mass and later, more intense pubertal growth spurts fueled by testosterone, which increases energy expenditure.

Key Points

Muscle Mass: Boys gain a higher percentage of lean muscle mass during puberty, a tissue that burns more calories at rest than fat tissue.
Metabolic Rate: A greater muscle mass gives boys a naturally higher resting metabolic rate, meaning they burn more calories throughout the day.
Hormonal Influence: Testosterone, the primary male hormone, promotes muscle synthesis and boosts appetite, while estrogen in females encourages fat storage.
Growth Spurt: Boys experience a later, more intense pubertal growth spurt, with peak height and weight velocity often coinciding, creating a surge in caloric need.
Fat Storage: Female metabolism is adapted for energy storage (fat), a strategy with evolutionary roots related to reproduction, resulting in generally lower caloric needs.
Physical Activity: Differences in average physical activity levels can also increase the caloric requirements for active boys compared to girls.

The Foundational Role of Muscle Mass

For many, the most significant reason behind the caloric difference is body composition, specifically muscle mass. On average, men have substantially more muscle mass than women. This difference is largely established during puberty, a period of rapid and distinct change for boys and girls. Muscle tissue is far more metabolically active than fat tissue, meaning it burns more calories even when the body is at rest. As boys transition through adolescence, rising testosterone levels fuel the development of a higher percentage of lean body mass, particularly in the upper body. This increased muscle mass creates a higher resting metabolic rate, requiring more fuel to maintain bodily functions throughout the day. Conversely, girls typically experience a greater increase in adipose (fat) tissue during puberty, which is less metabolically demanding than muscle.

Testosterone's Calorie-Burning Effect

Testosterone is the dominant hormone in male puberty and acts as a powerful driver for increased appetite and energy expenditure. It facilitates the accelerated growth of skeletal muscle, which in turn elevates a boy's basal metabolic rate (BMR). This hormonal shift creates a feedback loop: more testosterone leads to more muscle, which increases BMR, prompting the body to demand more food. For girls, the hormonal landscape of puberty is different. Estrogen promotes the accumulation of fat stores, which from an evolutionary perspective, is crucial for reproductive functions like gestation and lactation. This biological imperative to conserve energy is a key reason why girls' metabolism generally runs at a lower rate than boys'.

Puberty's Divergent Growth Timelines

While hormonal differences are a key driver, the timing and intensity of adolescent growth spurts also contribute to varying energy demands. Girls typically enter puberty earlier than boys, around ages 9-14, but their peak growth velocity occurs earlier and is less intense than that of boys. Boys enter their pubertal growth phase later, around ages 12-17, but their height and weight gain are more explosive and sustained. Studies show that for adolescent boys, the peak height and peak weight velocities often coincide, placing immense demands on the body's energy stores at one time. A study published in The American Journal of Clinical Nutrition found that during late puberty, males' observed energy intake was significantly higher than during earlier stages, consistent with this phase of rapid development. This intense, concentrated period of growth means boys have a massive, short-term need for additional energy and nutrients, manifesting as an increased appetite.

The Impact of Physical Activity

Beyond the physiological changes of puberty, differences in physical activity levels between boys and girls can also play a role. While generalizations should be avoided, some research suggests that adolescent boys may engage in more high-energy activities than their female peers. More vigorous physical activity directly translates to higher energy expenditure, necessitating greater caloric intake to fuel performance and recovery. A study found that for children and adolescents in rural developing countries, total energy expenditure was 10-25% higher for boys than girls, reflecting potentially different levels of habitual activity. This factor, combined with a larger baseline metabolic rate, further widens the caloric gap.

Comparative Factors Influencing Energy Needs


Feature	Average Boys (Adolescence)	Average Girls (Adolescence)
Muscle Mass	Higher lean body mass develops, particularly in upper body.	Higher adipose tissue develops, particularly in reproductive regions.
Dominant Hormone	Testosterone drives greater muscle synthesis and metabolic rate.	Estrogen influences fat storage patterns and nutrient partitioning.
Puberty Timing	Later onset (approx. 12-17 years), with a more intense, sustained growth spurt.	Earlier onset (approx. 9-14 years), with a shorter, less intense growth spurt.
Metabolic Rate	Higher resting metabolic rate due to greater muscle mass.	Lower resting metabolic rate compared to boys.
Growth Velocity	Peak height and weight velocity coincide, increasing energy demands simultaneously.	Peak height velocity occurs first, followed by peak weight velocity later.
Energy Strategy	Evolutionary tendency to mobilize energy stores for short-term muscle activity.	Evolutionary tendency to resist loss of fat stores for gestation and survival.

Understanding the Bigger Picture

The differences in energy requirements are a normal, natural part of development. It is important for parents and caregivers to understand these distinctions without reinforcing negative stereotypes or promoting unhealthy eating habits based on gender. Focusing on nutrient-dense foods, rather than simply restricting calories, is the right approach for both sexes. Providing balanced meals that include sufficient protein, healthy fats, and complex carbohydrates supports healthy growth, athletic performance, and overall well-being. For physically active boys, this may mean larger portions of protein and carbohydrates, while active girls will also require adequate fuel, especially iron due to menstruation. Education is key to navigating these changing nutritional needs during adolescence. By understanding the biological reasons behind the differences, we can provide better support for all children as they grow.

Conclusion

The difference in energy requirements between boys and girls is not a matter of simple appetite but a complex interplay of biology, hormones, and developmental timing. Boys generally need more calories to support greater muscle mass, a higher metabolic rate driven by testosterone, and a later, more intense growth spurt. Conversely, girls' metabolic strategies, influenced by estrogen, favor energy storage. Recognizing these natural, scientific variations allows for a more informed and supportive approach to adolescent nutrition, ensuring both boys and girls receive the right amount of fuel to thrive during this crucial period of development.

Source: For a deeper dive into gender differences in eating behavior, refer to the study "Gender differences in eating behavior and body weight concerns" via the National Institutes of Health.

Frequently Asked Questions

No, it is a normal and healthy part of development. Due to biological factors like greater muscle mass and higher energy needs during their growth spurt, boys naturally require more calories than girls of the same age.

Yes, absolutely. Muscle tissue is more metabolically active than fat tissue, meaning it requires more energy (calories) to maintain itself, even when you are at rest. Therefore, individuals with greater muscle mass have higher caloric needs.

During puberty, testosterone levels increase dramatically in boys, promoting muscle growth and a higher metabolic rate, which directly boosts their appetite. In girls, estrogen influences fat storage, which affects metabolic rate and calorie needs differently.

Yes, they do. Girls typically start puberty earlier but have a less intense growth spurt. Boys start later but experience a more explosive and sustained period of rapid growth, often with height and weight increases peaking at the same time.

While sex is a factor, an individual's body composition—specifically the amount of lean muscle mass—is the most significant determinant of their resting metabolic rate and overall caloric needs. Other factors include age, height, weight, and activity level.

Research indicates that, on average, boys are stronger than girls. The magnitude of this difference becomes most pronounced during male puberty and is more significant in the upper body musculature.

Parents should monitor nutritional quality and adequacy rather than just calories. Ensuring both boys and girls have a balanced diet of nutrient-dense foods is crucial. Because of their higher needs, active boys may need larger portions, but the focus should be on overall health, not strict calorie counting.

This is a biologically driven process influenced by hormones. Estrogen promotes fat storage, particularly in regions like the hips and thighs, which is an evolutionary mechanism to support reproductive function.