Nutrition Diet: Understanding What Causes a Higher BMR?

October 20, 2025 •

5 min read

Did you know that your basal metabolic rate (BMR) accounts for 60% to 70% of your body's total daily energy expenditure, fueling essential functions like breathing and blood circulation even at rest? Understanding what causes a higher BMR is key to managing your energy needs and overall metabolic health, as this baseline energy burn is shaped by a variety of inherent and lifestyle factors.

Quick Summary

The rate at which your body burns calories at rest, known as the basal metabolic rate, is influenced by several factors, including body composition, genetics, age, and hormones. While some aspects are fixed, others can be modified through lifestyle choices like diet and exercise.

Key Points

Muscle mass is key: Having more lean muscle mass directly increases your BMR, as muscle tissue burns more calories at rest than fat tissue.
Age slows metabolism: BMR naturally declines with age, mainly due to a gradual loss of muscle mass.
Genetics sets a baseline: Your inherited genetic makeup is a significant, unchangeable factor that influences your natural metabolic speed.
Hormones regulate the rate: The thyroid gland and its hormones are crucial for metabolic control; imbalances can cause your BMR to speed up or slow down.
Dietary habits matter: Severe calorie restriction lowers your BMR, but eating enough protein can slightly increase it due to the energy required for digestion.
Cold exposure boosts BMR: Your body expends more energy to stay warm in cold environments, leading to a temporary increase in BMR.

The Core Components of Your Basal Metabolic Rate

Your BMR is the amount of energy your body needs to maintain its most fundamental functions when you are at complete rest. It powers the unseen work of your body, from sustaining organ function to maintaining body temperature. Several key factors determine the rate of this core energy burn, some of which are outside your control.

Body Composition and Muscle Mass

One of the most significant and influential factors for a higher BMR is your body composition, specifically your lean muscle mass. Muscle tissue is far more metabolically active than fat tissue, meaning it burns more calories even when at rest. This is why individuals who engage in regular resistance training and have more muscle tend to have a higher BMR. As people age, a natural loss of muscle mass, known as sarcopenia, contributes to a decrease in BMR. This highlights the importance of incorporating strength-training exercises to maintain or increase muscle mass throughout life.

Age, Gender, and Genetics

Age is a major determinant of BMR, with rates typically declining as people get older. Infants and children have very high BMRs due to the energy demands of growth and development. After puberty, the rate gradually decreases, and this decline continues into old age, largely due to the age-related reduction in muscle tissue.

Gender also plays a significant role. On average, males have a higher BMR than females, primarily because men generally have more muscle mass and a larger overall body size. Hormonal differences, such as higher testosterone levels in men, also contribute to building muscle and further elevate the metabolic rate.

Your genetic makeup is another crucial, unchangeable factor. Some people are simply predisposed to have a naturally higher or lower BMR due to inherited traits. While you cannot alter your genetics, recognizing this predisposition can help you set realistic expectations for your body's metabolism and inform your lifestyle choices.

Hormonal and Environmental Influences

The thyroid gland is a major regulator of your metabolism, producing the hormones thyroxine (T4) and triiodothyronine (T3). An overactive thyroid, or hyperthyroidism, causes an increase in these hormones, leading to a higher BMR. Conversely, an underactive thyroid, or hypothyroidism, slows down metabolism and reduces BMR. Other hormonal shifts, such as those that occur during pregnancy, also lead to an increased BMR to support the development of the fetus.

Environmental temperature also influences BMR. When you are exposed to cold, your body must work harder to maintain its core temperature, a process known as thermogenesis. This increases your metabolic rate and burns extra calories, which can be further boosted by shivering. In contrast, hot environments cause a less significant increase as the body expends energy to cool down through sweating.

Lifestyle Factors That Impact BMR

While many factors are fixed, several lifestyle choices can be used to positively influence your BMR.

Diet and Nutrition: Drastically cutting calories can cause your body to enter a “starvation mode,” intentionally slowing your metabolism to conserve energy. Eating enough calories from a balanced diet, including regular meals, is crucial for maintaining a healthy BMR. The thermic effect of food (TEF), the energy burned during digestion, can also be leveraged. Protein has a higher TEF than fats and carbohydrates, meaning your body uses more energy to process it.
Exercise: Regular physical activity is vital. Resistance training builds and maintains muscle mass, which directly increases BMR. High-intensity interval training (HIIT) can also temporarily boost metabolism for hours after a workout, a phenomenon known as excess post-exercise oxygen consumption (EPOC). Even moderate, consistent exercise can contribute positively to your metabolic health.
Sleep: Chronic sleep deprivation can negatively impact your metabolism by affecting hormone levels and the body's ability to process carbohydrates. Getting adequate, restful sleep helps regulate the body's metabolic processes and supports overall energy levels.

Comparison of Factors Affecting BMR

To summarize the many influences on BMR, here is a comparison of fixed and modifiable factors:


Factor	How It Affects BMR	Modifiable?
Body Composition	Higher lean muscle mass leads to a higher BMR.	Yes (through exercise)
Age	BMR decreases with age due to muscle loss.	Not directly, but effects can be mitigated through lifestyle.
Gender	Males generally have a higher BMR than females due to greater muscle mass.	No (based on biological sex).
Genetics	Inherited traits can predispose an individual to a faster or slower metabolism.	No
Thyroid Hormones	An overactive thyroid increases BMR; an underactive one decreases it.	Yes (through medical treatment)
Body Size	Larger body size means more metabolizing tissue and a higher BMR.	No (based on natural proportions)
Environmental Temp.	Both cold and heat force the body to work to maintain its temperature, increasing BMR.	Yes (by controlling exposure)
Physical Activity	Regular resistance training and high-intensity exercise increase BMR.	Yes
Dietary Intake	Severe calorie restriction lowers BMR; adequate protein intake can increase it slightly.	Yes
Illness/Injury	The body's repair processes temporarily increase BMR.	No (it is a response to a medical event)

Important Considerations for a Higher BMR

It is important to remember that a higher BMR isn't always indicative of better health. In some cases, a very fast metabolism can be a symptom of underlying health issues, such as hyperthyroidism or hypermetabolism caused by a serious illness like cancer. Additionally, some studies have even found a correlation between a higher genetically predicted BMR and a reduced lifespan, though more research is needed in this complex area. A healthy, stable BMR is generally the goal for long-term well-being, rather than striving for the highest possible rate. Using your BMR as a component of a larger, more personalized nutrition and exercise plan is the most effective strategy for managing your weight and health.

Conclusion

Numerous factors, both inherent and controllable, contribute to what causes a higher BMR. While you cannot change your age, gender, or genetic blueprint, you can significantly influence your basal metabolic rate through smart lifestyle choices. Prioritizing strength-building exercise, maintaining a consistent and nutritious diet, and ensuring adequate sleep are powerful levers for supporting your metabolic health. Understanding these factors allows for a more personalized and sustainable approach to managing your energy needs, rather than relying on a one-size-fits-all solution.

Find more insights on managing your diet and health. Harvard Health

Frequently Asked Questions

While certain foods can have a minor effect on BMR through the thermic effect of food (e.g., protein), diet alone cannot drastically alter it. Eating enough calories and protein is more about preventing a metabolic slowdown than creating a major increase.

Regular aerobic exercise burns calories during the activity and offers many health benefits, but it does not have a significant long-term impact on BMR. Resistance training is more effective for boosting BMR by building lean muscle mass.

There can be considerable variation in BMR among individuals, even those of the same age, sex, and size. Factors like genetics and the size of internal organs can cause a BMR to differ by as much as 10%.

Not necessarily. A very high BMR can be a symptom of underlying health issues like hyperthyroidism. Some genetic studies have also linked a higher-than-average BMR with reduced lifespan. A stable, healthy BMR is generally the target for well-being.

Inadequate sleep can negatively impact your metabolism. It can disrupt the regulation of hormones that control appetite and energy use, and can also lead to reduced fat-burning efficiency, ultimately affecting your BMR.

On average, yes, men tend to have a higher BMR than women due to having more lean muscle mass and a larger overall body size. However, once lean body mass is accounted for, the BMR differences are not as significant.

Chronic stress can influence metabolism through the hormone cortisol. High levels of cortisol can disrupt metabolic balance and fat storage, impacting BMR. Managing stress is important for maintaining a stable metabolic rate.