7 Factors influencing your basal metabolic rate

Understanding your Basal Metabolic Rate (BMR) is crucial for optimizing your health and wellness. BMR, the rate at which your body burns calories at rest, significantly impacts your energy levels and overall well-being [1]. 

You may wonder why some people seem to eat without gaining weight, or why weight loss efforts vary so widely from person to person. The answer often lies in the intricacies of BMR. 

This article aims to guide you through the essential factors that influence your BMR, offering insights and advice to help you make informed decisions about your health. 

As you read on, you’ll better understand how BMR functions and how you can effectively manage it for a healthier lifestyle.

What are the factors affecting your BMR?

1. Age

As you age, changes in your body composition and metabolic processes affect how efficiently your body burns calories. Here’s how age impacts your BMR:

  • Decrease in muscle mass: Starting in your 30s, you gradually lose muscle mass, a key player in maintaining a higher BMR [2]. Muscle tissue burns more calories than fat, even at rest. This loss results in a slower metabolism as you age.
  • Hormonal changes: Aging is accompanied by hormonal shifts that can slow down metabolic processes. For instance, women experience a significant drop in estrogen during menopause, which can lead to a lower BMR.
  • Reduced physical activity: Often, older adults engage in less physical activity, leading to reduced muscle mass and a lower BMR. This creates a cycle where decreased activity leads to a slower metabolism, which can further reduce energy levels and physical activity.

However, this doesn’t mean a declining BMR is inevitable. You can take steps to counteract these natural changes:

  • Regular exercise: Incorporating strength training and aerobic exercises can help maintain or even increase muscle mass, boosting your basal metabolic rate (BMR).

2. Body composition

Your body composition refers to the ratio of fat, muscle, and bone in your body.  Unlike age, which you cannot control, body composition is a factor you can actively manage to impact your BMR. Here’s how:

  • Muscle mass vs. fat: Muscle tissue is metabolically more active than fat tissue. This means that individuals with higher muscle mass typically have a higher BMR because muscles require more energy to maintain. In contrast, a higher percentage of body fat usually corresponds to a lower BMR.
  • Impact of weight loss: When you lose weight, especially through diet alone without exercise, you might lose muscle mass along with fat. This can inadvertently lower your BMR, making it harder to lose weight or maintain weight loss.
  • The role of exercise: Regular strength training and cardiovascular exercises help build muscle mass and reduce fat. This not only enhances your BMR but also improves your overall health.

To positively influence your BMR through body composition, focus on:

  • Strength training: Incorporate resistance training into your routine to build and maintain muscle mass.
  • Balanced nutrition: For optimal muscle growth and maintenance, consume a diet rich in lean protein, complex carbohydrates, and healthy fats [3].

3. Gender

Typically, men and women have different BMRs due to inherent biological differences, particularly in body composition and hormonal makeup. Here’s a closer look at how gender affects BMR:

  • Body composition differences: Men generally have a higher muscle mass compared to women [4], contributing to a naturally higher BMR. Since muscle tissue burns more calories than fat tissue, even at rest, men typically have a faster metabolism.
  • Hormonal influences: Hormones play a significant role in regulating metabolism. For example, the male hormone testosterone helps in building muscle, which boosts BMR. Women have higher levels of estrogen, which can lead to a higher body fat percentage, often resulting in a lower BMR.
  • Impact of menstrual cycle: Women’s BMR can fluctuate during the menstrual cycle. Some studies suggest that BMR may increase slightly during the luteal phase, post-ovulation, due to hormonal changes.

Despite these general trends, it’s important to remember that individual variations exist. Lifestyle choices, such as diet and exercise, can significantly influence BMR, regardless of gender. 

4. Genetic factors

Genetic makeup is a crucial yet often overlooked component influencing Basal Metabolic Rate (BMR). Your genes play a significant role in determining your body’s efficiency in burning calories and overall metabolic health. Here’s an insight into how genetics impact BMR:

  • Inherited metabolic rate: Just like eye color or height, aspects of your metabolism are inherited. Some people are genetically predisposed to have a faster or slower BMR. This genetic variance explains why metabolic rates can differ significantly among individuals, even under similar conditions.
  • Genetic influence on body composition: Your genes also affect your body composition, including the proportion of muscle to fat [5]. People with a genetic predisposition for higher muscle mass will naturally have a higher BMR.
  • Metabolic disorders: Certain genetic conditions can affect metabolism. For example, conditions like hypothyroidism or Cushing’s syndrome, which can be influenced by genetics, directly impact metabolic rate.

While you can’t change your genetic makeup, understanding its role in your BMR empowers you to make more informed choices about your health and wellness.

Through a combination of healthy habits, you can optimize your BMR for better health outcomes.

5. Hormonal balance

Hormones, acting as the body’s chemical messengers, play a pivotal role in regulating metabolism. Imbalances in key hormones can significantly alter how efficiently your body burns calories. Here’s how hormonal balance impacts BMR:

  • Thyroid hormones: Thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3), are central to metabolic regulation [6]. An underactive thyroid (hypothyroidism) can slow down metabolism [7], reducing BMR, whereas an overactive thyroid (hyperthyroidism) can do the opposite.
  • Insulin: Insulin, secreted by the pancreas, regulates glucose metabolism. Insulin resistance, a condition where cells don’t respond effectively to insulin, can lead to metabolic syndrome, impacting BMR.
  • Cortisol: Known as the stress hormone, cortisol influences metabolism. Chronic high levels of cortisol can lead to increased fat storage, particularly around the abdomen, and can disrupt metabolic balance.
  • Sex hormones: Estrogen and testosterone also influence BMR. For instance, women might experience metabolic changes during the menstrual cycle, pregnancy, and menopause due to fluctuating estrogen levels.

Maintaining hormonal balance is key to a healthy BMR. This involves:

  • Stress management: Reducing stress can help regulate cortisol levels.
  • Healthy diet: A balanced diet supports overall hormonal health.
  • Regular exercise: Physical activity can help maintain insulin sensitivity and hormonal balance.

6. Physical activity levels

Engaging in regular physical activity not only burns calories during the activity itself but also has a profound effect on your overall metabolism. Here’s how physical activity impacts BMR:

  • Boosting muscle mass: Exercise, especially strength training, builds muscle mass. Since muscle tissue is more metabolically active than fat, increasing your muscle mass raises your BMR. This means your body will burn more calories at rest.
  • Enhanced metabolic efficiency: Regular physical activity improves the body’s efficiency in energy utilization. Over time, your body becomes better at managing energy resources, which positively affects metabolic rate.
  • Post-exercise oxygen consumption: After intense exercise, your body continues to burn more calories as it returns to its resting state, a phenomenon known as Excess Post-Exercise Oxygen Consumption (EPOC) [8]. This effect temporarily boosts your BMR.

To leverage physical activity for improving BMR, consider:

  • Consistency: Regular exercise is key. Aim for a mix of cardiovascular workouts and strength training for optimal results.
  • Intensity: Higher intensity workouts can lead to a more significant EPOC effect.
  • Variety: Mixing up your workout routine can challenge your body in different ways, preventing plateaus in metabolic rate.

7. Environmental factors

Your body works constantly to maintain a stable internal temperature, and variations in external temperature can impact how much energy is expended in this process. Here’s how different temperatures affect BMR:

  • Cold environments: When exposed to cold, your body must work harder to maintain its core temperature [9]. This process, known as thermogenesis, leads to an increase in BMR. Activities like shivering also burn additional calories, further boosting metabolic rate.
  • Warm environments: In contrast, in warm environments, your body expends less energy on heat production. While sweating and the body’s efforts to cool down do consume energy, the overall impact on BMR is typically less pronounced compared to cold environments.
  • Adaptive thermogenesis: Over time, your body can adapt to consistent cold or warm environments, which can lead to changes in your BMR. For instance, regular exposure to cold may enhance your body’s efficiency in heat production and fat metabolism.

To leverage environmental temperature for BMR optimization, consider:

  • Regular exposure to mild cold: This can increase your body’s metabolic rate over time, improving your ability to burn calories.

Balanced exposure: While using temperature to influence BMR, it’s important to maintain a balance and avoid extreme conditions that might be harmful.

environmental factors

Closing thoughts

Understanding the various factors that influence your Basal Metabolic Rate is a key step towards optimizing your health and wellness. 

From age and gender to genetics and physical activity, each element plays a distinct role in determining how efficiently your body burns calories. 

Armed with this knowledge, you are now better equipped to make informed decisions and adopt lifestyle practices that can positively impact your BMR. 

Remember, small, consistent changes in your daily habits can lead to significant improvements in your metabolic health, paving the way for a more energetic and healthier life.


What are the 3 components of BMR?

The three components of Basal Metabolic Rate (BMR) are genetic factors, age, and body composition. These elements collectively determine how efficiently your body burns calories at rest, influencing overall metabolic health.

What are 5 factors that can increase your BMR?

Five factors that can increase your Basal Metabolic Rate (BMR) are regular physical activity, building muscle mass, maintaining hormonal balance, exposure to cold temperatures, and a balanced, nutritious diet. These factors enhance the body’s calorie-burning efficiency at rest.

What is the single most important factor affecting BMR?

The single most important factor affecting Basal Metabolic Rate (BMR) is body composition, specifically the ratio of muscle to fat. Higher muscle mass significantly increases BMR, as muscles are more metabolically active than fat tissue.

What is the best basal metabolic rate?

The “best” Basal Metabolic Rate (BMR) is subjective and varies individually, depending on factors like age, sex, and body composition. An optimal BMR for an individual supports their specific health goals and overall well-being.

[1] https://en.wikipedia.org/wiki/Basal_metabolic_rate
[2] https://www.webmd.com/healthy-aging/how-much-does-your-metabolism-slow-down-as-you-age 
[3] https://www.healthline.com/nutrition/bodybuilding-meal-plan 
[4] https://journals.physiology.org/doi/full/10.1152/jappl.2000.89.1.81
[5] https://pubmed.ncbi.nlm.nih.gov/9421240/
[6] https://www.nhs.uk/conditions/underactive-thyroid-hypothyroidism/
[7] https://www.mayoclinic.org/diseases-conditions/hyperthyroidism/symptoms-causes/syc-20373659
[8] https://blog.nasm.org/excess-post-exercise-oxygen-consumption
[9] https://www.froedtert.com/stories/how-cold-weather-affects-body-during-exercise

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