LOSE WEIGHT WITH MEDICAL SUPPORT — BUILT FOR MEN
- Your personalised programme is built around medical care, not willpower.
- No generic diets. No guesswork.
- Just science-backed results and expert support.
Find out if you’re eligible
Does increased muscle mass increase metabolism? This question frequently arises in discussions about weight management and metabolic health. Muscle tissue is metabolically active, requiring energy even at rest, which contributes to your resting metabolic rate (RMR). Research confirms that individuals with greater muscle mass do have higher baseline energy expenditure compared to those with less muscle. However, the magnitude of this metabolic increase is more modest than popular fitness narratives often suggest. Understanding the relationship between muscle mass and metabolism requires examining the underlying science, realistic expectations, and the broader context of factors influencing metabolic rate.
Quick Answer: Increased muscle mass does increase metabolism, with each kilogram of muscle raising resting metabolic rate by approximately 10-15 kcal per day, though this effect is more modest than commonly claimed.
Muscle tissue is metabolically active, meaning it requires energy even when you are at rest. Your resting metabolic rate (RMR) represents the number of calories your body burns to maintain basic physiological functions such as breathing, circulation, and cellular repair. Skeletal muscle contributes significantly to this baseline energy expenditure, though the extent of its contribution is often misunderstood in popular health discourse.
Research indicates that muscle tissue burns approximately 10-15 kcal per kilogram per day at rest, whilst adipose (fat) tissue burns roughly 3-6 kcal per kilogram per day. This difference means that individuals with greater muscle mass do indeed have a higher resting metabolic rate compared to those with less muscle mass, all other factors being equal. However, the magnitude of this effect is more modest than many fitness publications suggest.
The relationship between muscle mass and metabolism extends beyond simple calorie calculations. Muscle tissue plays a crucial role in glucose metabolism and insulin sensitivity, which are fundamental to metabolic health. Increased muscle mass improves the body's ability to regulate blood sugar levels and may reduce the risk of metabolic disorders such as type 2 diabetes. This metabolic benefit occurs through enhanced glucose uptake by muscle cells, particularly following physical activity, as supported by NICE guidance on type 2 diabetes prevention (PH38).
It is important to recognise that whilst building muscle does increase metabolic rate, this represents just one component of total daily energy expenditure. Physical activity, the thermic effect of food (energy used to digest and process nutrients), and non-exercise activity thermogenesis (NEAT) all contribute substantially to overall calorie expenditure throughout the day.
LOSE WEIGHT WITH MEDICAL SUPPORT — BUILT FOR MEN
Find out if you’re eligible
At the cellular level, muscle tissue contains mitochondria—the organelles responsible for producing adenosine triphosphate (ATP), the body's primary energy currency. Mitochondrial density varies by muscle fibre type, with Type I (slow-twitch) fibres having greater mitochondrial content than Type II (fast-twitch) fibres. This mitochondrial presence contributes to why muscle tissue has greater metabolic demands than many other tissues. Even during periods of rest, muscle cells maintain protein synthesis, ion gradient regulation, and other energy-requiring processes that contribute to basal metabolic rate.
The metabolic activity of muscle varies depending on muscle fibre type. Type I (slow-twitch) fibres are more oxidative and rely primarily on aerobic metabolism, whilst Type II (fast-twitch) fibres are more glycolytic and suited to anaerobic activity. Both fibre types contribute to resting energy expenditure, though their metabolic profiles differ. Resistance training primarily influences adaptations within Type II fibre subtypes (particularly conversion from Type IIx to IIa) and increases the cross-sectional area of muscle fibres, thereby enhancing overall metabolic capacity.
Key metabolic processes in muscle tissue include:
Protein turnover – the continuous breakdown and synthesis of muscle proteins, which requires substantial energy
Maintenance of sodium-potassium pumps – essential for cellular function and nerve signal transmission
Calcium cycling – necessary for muscle contraction and relaxation mechanisms
Substrate metabolism – the processing of glucose, fatty acids, and amino acids for energy production
Research published in peer-reviewed journals demonstrates that the metabolic rate of muscle tissue can increase during and after exercise, a phenomenon known as excess post-exercise oxygen consumption (EPOC). This elevated metabolic state can persist for several hours following intense physical activity, particularly after resistance training or high-intensity interval training. The magnitude of EPOC is typically modest, contributing approximately 6-15% additional energy expenditure following exercise. However, the contribution of EPOC to long-term weight management remains a subject of ongoing scientific investigation.
Quantifying the precise metabolic increase from gaining muscle mass requires careful consideration of the available evidence. Studies suggest that each kilogram of muscle gained increases resting metabolic rate by approximately 10-15 kcal per day. This means that if an individual gains 2.3 kilograms (approximately 5 pounds) of muscle through a structured resistance training programme, their resting metabolic rate would increase by roughly 30 kcal per day—equivalent to about half a plain digestive biscuit.
Whilst this figure may seem modest, it is important to contextualise these findings. The metabolic benefit of increased muscle mass accumulates over time and represents an elevation in baseline energy expenditure, provided the muscle mass is maintained. Over the course of a year, an additional 30 kcal per day equates to approximately 10,950 kcal, which could theoretically prevent some of the gradual weight gain that many adults experience with ageing.
However, the total metabolic impact of resistance training extends beyond the resting metabolic rate increase from muscle tissue alone. The act of building muscle through progressive resistance exercise burns substantial calories during training sessions. Additionally, the recovery and repair processes following resistance training elevate metabolic rate for up to 24 hours post-exercise, though this effect is typically modest. When these factors are combined, the overall metabolic benefit of a resistance training programme becomes more clinically significant.
Realistic expectations for metabolic changes:
Gaining 4.5 kilograms of muscle may increase RMR by approximately 45-70 kcal per day
The metabolic boost persists only if muscle mass is maintained through continued training
Individual responses vary based on genetics, age, hormonal status, and training intensity
The indirect benefits (improved insulin sensitivity, enhanced physical activity capacity) may be more significant than the direct metabolic increase
It is worth noting that there is no official link between muscle gain and dramatic metabolic transformation in the absence of other lifestyle modifications. Claims suggesting that building muscle will substantially accelerate weight loss should be viewed with appropriate scepticism.
Whilst muscle mass contributes to metabolic rate, numerous other factors exert significant influence on total energy expenditure. Understanding these variables provides a more comprehensive picture of metabolic health and helps set realistic expectations for individuals seeking to optimise their metabolism.
Body composition and organ metabolism: Internal organs, particularly the liver, brain, heart, and kidneys, are highly metabolically active and collectively account for approximately 60-70% of resting energy expenditure, despite representing only about 5% of body weight. In contrast, skeletal muscle accounts for roughly 20% of resting metabolic rate in sedentary individuals. This distribution highlights that muscle mass, whilst important, is not the predominant determinant of baseline metabolism.
Age-related metabolic changes: Recent research suggests that resting metabolic rate remains relatively stable from early adulthood until around age 60, after which a more noticeable decline occurs. This decline is associated with age-related loss of muscle mass (sarcopenia) and changes in organ metabolism. However, research indicates that much of this decline can be attenuated through regular physical activity and resistance training. The metabolic decline associated with ageing is not inevitable and can be substantially modified through lifestyle interventions.
Hormonal influences: Thyroid hormones, particularly triiodothyronine (T3) and thyroxine (T4), are primary regulators of metabolic rate. Hypothyroidism can reduce metabolic rate significantly, whilst hyperthyroidism can increase it substantially. Other hormones including cortisol, growth hormone, testosterone, and oestrogen also influence metabolic rate through various mechanisms. Individuals experiencing unexplained changes in weight or energy levels should consult their GP to exclude endocrine disorders. The NHS provides information on symptoms of thyroid disorders that warrant medical attention.
Genetic factors: Studies suggest that genetic variation contributes moderately to the inter-individual differences in resting metabolic rate. Certain genetic polymorphisms affect mitochondrial function, thyroid hormone activity, and the efficiency of energy metabolism. Whilst genetics cannot be modified, understanding their role helps explain why metabolic rates vary considerably between individuals of similar body composition.
Additional metabolic influences include:
Sex – men typically have 5-10% higher metabolic rates than women due to greater muscle mass and lower body fat percentage
Body size – larger individuals have higher absolute metabolic rates but may have lower rates per kilogram of body weight
Dietary factors – severe calorie restriction can reduce metabolic rate by 15-30% through adaptive thermogenesis
Sleep quality – chronic sleep deprivation may reduce metabolic rate and impair glucose metabolism
Environmental temperature – exposure to cold increases metabolic rate through thermogenic mechanisms
Medications – certain medicines can influence energy expenditure and weight; discuss with your GP or pharmacist if concerned
Supporting optimal metabolic function requires a multifaceted approach that extends beyond simply building muscle mass. Evidence-based strategies focus on sustainable lifestyle modifications that enhance overall metabolic health whilst promoting long-term wellbeing.
Progressive resistance training: The UK Chief Medical Officers' Physical Activity Guidelines recommend that adults engage in muscle-strengthening activities on at least two days per week, alongside 150 minutes of moderate-intensity aerobic activity (or 75 minutes of vigorous activity) weekly. A structured resistance training programme that progressively increases load and volume can effectively build muscle mass and improve metabolic health. Exercises should target all major muscle groups, including legs, hips, back, abdomen, chest, shoulders, and arms. For individuals new to resistance training, consultation with a qualified exercise professional can ensure proper technique and appropriate progression.
Adequate protein intake: Protein consumption supports muscle protein synthesis and has a higher thermic effect than carbohydrates or fats, meaning the body expends more energy digesting and processing protein. The British Dietetic Association advises that general adults need approximately 0.75g of protein per kg of body weight daily. Those regularly engaging in strength training may benefit from higher intakes of 1.2-2.0g per kg of body weight per day to optimise muscle growth. Protein should be distributed relatively evenly across meals to maximise muscle protein synthesis throughout the day. People with kidney disease should consult with a healthcare professional before increasing protein intake.
Sufficient sleep and stress management: Sleep deprivation disrupts metabolic hormones including leptin, ghrelin, cortisol, and growth hormone, potentially reducing metabolic rate and increasing appetite. Adults should aim for 7-9 hours of quality sleep per night. Chronic psychological stress elevates cortisol levels, which can promote muscle breakdown and fat accumulation, particularly in the abdominal region. Stress management techniques such as mindfulness, regular physical activity, and social connection support metabolic health.
Avoiding severe calorie restriction: Whilst calorie deficits are necessary for weight loss, excessively restrictive diets can trigger metabolic adaptation, reducing resting metabolic rate. This adaptive response, sometimes termed "metabolic slowdown," represents the body's attempt to conserve energy during perceived famine. Moderate calorie deficits (approximately 500 kcal per day) combined with adequate protein intake and resistance training help preserve muscle mass and minimise metabolic adaptation.
When to seek medical advice:
Unexplained weight gain or loss (particularly >5% of body weight within 6-12 months)
Persistent fatigue, cold intolerance, or heat sensitivity suggesting thyroid dysfunction
Difficulty building or maintaining muscle mass despite appropriate training
New symptoms such as increased thirst, frequent urination, palpitations, or neck swelling
Concerns about metabolic health or body composition changes
Your GP can arrange appropriate investigations including thyroid function tests, HbA1c (for diabetes screening), assessment of other hormonal parameters, and evaluation for underlying medical conditions that may affect metabolism. In some cases, referral to an endocrinologist or HCPC-registered dietitian may be appropriate for specialised assessment and management. Remember that metabolic health encompasses far more than simply the number of calories burned at rest—it reflects the complex interplay of multiple physiological systems that support overall health and wellbeing.
Muscle tissue burns approximately 10-15 kcal per kilogram per day at rest, whilst adipose (fat) tissue burns roughly 3-6 kcal per kilogram per day. This difference contributes to higher resting metabolic rates in individuals with greater muscle mass.
Each kilogram of muscle gained increases resting metabolic rate by approximately 10-15 kcal per day. Gaining 4.5 kg of muscle may increase RMR by roughly 45-70 kcal daily, which is modest but accumulates over time if muscle mass is maintained through continued training.
Internal organs (liver, brain, heart, kidneys) account for 60-70% of resting energy expenditure. Other factors include thyroid hormones, age, sex, body size, sleep quality, stress levels, genetic variation, and dietary factors such as severe calorie restriction.
All medical content on this blog is created based on reputable, evidence-based sources and reviewed regularly for accuracy and relevance. While we strive to keep content up to date with the latest research and clinical guidelines, it is intended for general informational purposes only.
DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
