Which of the following can affect RMR?: A Comprehensive Guide

December 29, 2025 •

4 min read

Accounting for approximately 60-70% of your total daily energy expenditure, Resting Metabolic Rate (RMR) represents the calories your body burns at rest to perform essential functions. This baseline calorie burn is not static, as a variety of factors, both controllable and uncontrollable, can significantly influence it throughout your life.

Quick Summary

A multitude of factors influence resting metabolic rate, including age, gender, body composition, genetics, hormones, diet, sleep, and physical activity levels. Understanding these elements provides insight into how the body uses energy, aiding in effective weight management and health planning.

Key Points

Body Composition: Your ratio of lean muscle mass to fat mass is the most significant and modifiable factor affecting RMR, with muscle being far more metabolically active.
Age and Gender: Age-related muscle loss can slow RMR, and men typically have a higher RMR than women due to greater muscle mass, though this evens out when adjusted for body composition.
Dietary Habits: Severely restricting calories slows down RMR, while a higher intake of protein can temporarily increase it through the thermic effect of food.
Sleep and Stress: Insufficient sleep and chronic stress, particularly from elevated cortisol, are linked to a reduced RMR and metabolic dysfunction.
Physical Activity: Incorporating resistance training and high-intensity interval training (HIIT) effectively builds muscle and provides a metabolic boost, positively influencing RMR.
Hormonal Balance: Thyroid hormones are a crucial regulator of RMR, and imbalances (like hypothyroidism) can significantly decrease your metabolic rate.

Introduction to Resting Metabolic Rate (RMR)

Your RMR is the energy your body expends while at rest to maintain fundamental physiological functions like breathing, circulating blood, and regulating temperature. While it is a foundational measure of your daily energy needs, it is not a fixed number. Many variables contribute to your unique metabolic profile, and understanding them is crucial for setting realistic health and fitness goals. From the metabolic activity of your tissues to the quality of your sleep, numerous elements can shift your RMR up or down.

Uncontrollable Factors Affecting RMR

Some determinants of your RMR are largely beyond your control. These biological factors establish a metabolic baseline that you work with throughout your life.

Age and Gender

Age: Your RMR tends to decline as you get older, a phenomenon partly explained by a natural loss of muscle mass. After the initial growth peak in your late teens and early twenties, your RMR can decrease by about 2% per decade. However, some studies suggest this decline is not solely tied to changes in body composition, pointing to a potential slowdown in tissue-specific metabolic rates.
Gender: Men typically have a higher RMR than women of similar age and weight. This difference is largely attributed to body composition, as men generally have a higher proportion of lean muscle mass, which is more metabolically active than fat tissue. When RMR is adjusted for body mass and fat-free mass, the difference between sexes becomes less significant, especially in athletic populations.

Genetics and Ethnicity

Genetics: Your genes play a role in determining your metabolic rate. Some people are genetically predisposed to having a naturally faster or slower metabolism. Over 100 genes have been identified that can influence RMR and obesity risk.
Ethnicity: Research has indicated variations in RMR among different ethnic groups, even after adjusting for body composition. This may be linked to differences in organ size and the distribution of lean body mass.

Hormonal Influences

Thyroid Hormones: The thyroid gland produces hormones like T3 and T4 that are primary regulators of your metabolic rate. Hypothyroidism (underactive thyroid) can significantly slow down your RMR, leading to weight gain and fatigue. Conversely, hyperthyroidism can speed it up.
Stress Hormones: Chronic stress elevates the hormone cortisol, which can disrupt metabolic function. Prolonged HPA axis (hypothalamic–pituitary–adrenal) activation can lead to metabolic dysfunction, contributing to weight gain and insulin resistance.

Controllable Lifestyle Factors that Affect RMR

While you can't change your age or genetics, several lifestyle factors offer opportunities to positively influence your RMR.

Body Composition and Physical Activity

Your ratio of lean body mass (muscle and organs) to fat mass is one of the most powerful and modifiable factors influencing RMR. Muscle tissue is far more metabolically active than fat tissue, burning more calories at rest.

Resistance Training: Building and maintaining muscle mass through weightlifting and bodyweight exercises is a primary way to increase your RMR. This can help counteract the natural age-related decline in metabolism.
High-Intensity Interval Training (HIIT): Incorporating HIIT can also temporarily boost your RMR for a period after the workout is complete.

Diet and Nutrition

Calorie Intake: Drastically restricting your calorie intake can cause your body to enter a “starvation mode,” significantly lowering your RMR to conserve energy. Severe caloric restriction can suppress RMR by as much as 20%. To maintain a healthy RMR during weight loss, creating a moderate calorie deficit is essential.
Protein Intake: The thermic effect of food (TEF) is the energy required to digest and process food. Protein has the highest TEF of all macronutrients, requiring 20-30% of its calories for digestion, compared to 5-10% for carbs and 0-3% for fat. A higher-protein diet can therefore slightly boost your RMR.
Hydration: Even mild dehydration can slow down your metabolism. Drinking enough water is crucial for all metabolic processes to function efficiently.

Sleep and Stress Management

Sleep: Chronic sleep restriction is associated with a lower RMR, as your body attempts to conserve energy. In addition, sleep deprivation can negatively impact hormones that regulate appetite, leading to cravings for high-fat and high-sugar foods.
Stress: While acute stress can temporarily increase RMR, chronic stress and high cortisol levels can impair metabolic function and promote fat storage, especially in the abdominal area. Effective stress management is key to maintaining a healthy metabolic rate.

RMR Determinants: A Comparison


Factor	Impact on RMR	Explanation	Controllable?
Body Composition	Highly Significant	Lean muscle tissue burns far more calories at rest than fat tissue.	Yes
Age	Decreases over time	RMR slows down by ~2% per decade after early adulthood due to muscle loss and other factors.	No (but can be mitigated)
Gender	Significant (Male > Female)	Men generally have a higher RMR due to greater lean body mass.	No
Genetics	Significant (Inter-individual variability)	Influences how fast or slow your metabolism is naturally.	No
Hormones	Significant	Thyroid hormones are direct regulators; stress hormones like cortisol can disrupt metabolism.	Sometimes (with medical help)
Diet	Significant	Severe caloric restriction lowers RMR; protein intake increases the thermic effect of food.	Yes
Sleep	Significant	Chronic sleep deprivation can lower RMR to conserve energy.	Yes
Physical Activity	Significant	Resistance training increases muscle mass, boosting RMR; HIIT provides a temporary post-workout boost.	Yes
Environmental Temp	Minimal/Temporary	Extreme cold or heat forces the body to expend energy to regulate core temperature.	Yes

Conclusion: Taking Control of Your RMR

While some factors influencing your RMR, such as age and genetics, are unchangeable, many others are within your control. By focusing on modifiable lifestyle factors, you can effectively manage and optimize your resting metabolic rate for better health outcomes. Prioritizing resistance training to build muscle, maintaining a balanced diet, ensuring adequate sleep, and managing stress are all powerful strategies. Recognizing the interplay between your biology and your lifestyle empowers you to make informed decisions that support your metabolism and overall well-being.

For more information on the intricate relationships between metabolic rate and aging, a comprehensive review of relevant studies can be found on the National Institutes of Health website.

Frequently Asked Questions

RMR (Resting Metabolic Rate) and BMR (Basal Metabolic Rate) both measure the calories your body burns at rest. However, RMR is measured under less strict conditions, including minimal daily activity like digestion, while BMR is measured under complete rest in a lab. RMR is typically about 10% higher than BMR and is more commonly used.

Yes, losing weight can cause a decrease in RMR, a phenomenon known as metabolic adaptation. This happens because a smaller body requires fewer calories to function. However, the drop can be minimized by incorporating regular resistance training to preserve lean muscle mass.

Yes, certain types of exercise can increase your RMR. Resistance training builds muscle, and because muscle is more metabolically active than fat, it increases the number of calories you burn at rest. HIIT can also provide a temporary metabolic boost after the workout is over.

Chronic sleep deprivation can lead to a lower RMR as your body tries to conserve energy. It can also disrupt hormones like leptin and ghrelin, which regulate appetite, potentially leading to weight gain.

Yes, genetics play a role in determining your metabolic rate, accounting for some of the individual variation. Your genes can influence factors like muscle size and hormonal function, which in turn affect RMR.

Yes. Severe calorie restriction can lower your RMR, while a healthy, balanced diet with adequate protein intake can support a healthy metabolic rate. Protein, in particular, requires more energy to digest, which provides a small boost to RMR.

Hormones are key regulators of RMR. Thyroid hormones, for instance, significantly impact your metabolic speed. Imbalances from chronic stress (cortisol) can also negatively affect metabolic function.