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
Resting energy calories, clinically termed resting energy expenditure (REE) or resting metabolic rate (RMR), represent the calories your body burns at complete rest to sustain vital functions like breathing, circulation, and cellular metabolism. REE typically accounts for 60 to 75 percent of total daily calories burned, making it the largest component of energy expenditure for most people. Understanding your resting energy needs provides a foundation for personalized nutrition planning, weight management strategies, and metabolic health assessment. Healthcare providers use REE measurements to establish appropriate caloric targets and identify potential metabolic concerns requiring further evaluation.
Quick Answer: Resting energy calories (REE) are the calories your body burns at complete rest to maintain essential functions like breathing and circulation, typically representing 60-75% of total daily energy expenditure.
Resting energy calories, more formally known as resting energy expenditure (REE) or resting metabolic rate (RMR), refers to the number of calories your body burns while at complete rest to maintain essential physiological functions. These functions include breathing, circulation, cellular metabolism, protein synthesis, and maintaining body temperature. REE represents the largest component of total daily energy expenditure in most individuals, typically accounting for 60 to 75 percent of all calories burned each day, though this percentage varies based on activity level and body composition.
The term is often used interchangeably with basal metabolic rate (BMR), though there are subtle differences. BMR is measured under highly standardized conditions—after an overnight fast, in a thermoneutral environment, and immediately upon waking before any physical activity. REE/RMR measurements are slightly less stringent but still require the individual to be at rest for at least 15 to 30 minutes before assessment. RMR values are typically about 10% higher than BMR due to these less restrictive measurement conditions.
Understanding resting energy calories is clinically important because it provides a baseline for determining total caloric needs. This baseline helps healthcare providers develop appropriate nutrition plans for weight management, recovery from illness, or metabolic disorders. For patients, knowing their REE can inform realistic expectations about caloric intake and weight loss or gain trajectories.
REE is expressed in kilocalories per day (kcal/day) or kilojoules per day (kJ/day), with one kilocalorie equaling approximately 4.184 kilojoules. In everyday language, when people refer to "calories," they typically mean kilocalories, the unit used on nutrition labels and in dietary guidance. It's worth noting that consumer fitness devices and apps that estimate "resting calories" may have error margins of 10-20% compared to clinical measurements.
LOSE WEIGHT WITH MEDICAL SUPPORT — BUILT FOR MEN
Find out if you’re eligible
Multiple physiological and demographic factors influence an individual's resting energy expenditure, making REE highly variable across populations. Body composition is the most significant determinant—lean body mass (muscle, organs, bone) is metabolically active tissue that requires substantially more energy at rest than adipose (fat) tissue. Individuals with greater muscle mass typically have higher REE values, which partially explains why men generally have higher resting energy expenditure than women of similar weight.
Age progressively affects REE throughout the lifespan. Infants and children have elevated metabolic rates relative to body size due to growth demands. REE typically peaks in early adulthood and then declines by approximately 1 to 2 percent per decade after age 30, primarily due to age-related loss of lean body mass (sarcopenia) and changes in organ metabolic activity. This decline contributes to the increased difficulty many adults experience maintaining stable weight as they age.
Sex influences REE independently of body size and composition. Men typically have slightly higher REE than women, even after adjusting for differences in lean body mass, though these residual differences are modest and vary by measurement methods.
Genetic factors contribute to inter-individual variation in REE, with twin studies suggesting a heritable component, though estimates vary widely depending on study populations and methodologies.
Thyroid function significantly impacts REE—clinically overt hypothyroidism typically decreases REE by 5 to 15 percent (with severe untreated cases potentially higher), while hyperthyroidism can increase it by 10 to 30 percent or more. Environmental temperature affects REE through both shivering and non-shivering thermogenesis, with cold exposure increasing energy expenditure. Medications may influence REE—stimulants may modestly increase it, while some beta-blockers might slightly decrease it, though effects vary by individual and specific medication.
Nutritional status impacts REE—prolonged caloric restriction can decrease REE by 10 to 15 percent through metabolic adaptation. Acute illness or injury typically elevates REE through inflammatory and stress responses. Fever increases REE by approximately 7 percent per degree Fahrenheit (or about 13 percent per degree Celsius). Pregnancy progressively increases REE across gestation to support fetal development, while lactation requires additional energy for milk production.
Resting energy expenditure measurements serve multiple important clinical applications across various medical specialties. In weight management, accurate REE determination allows clinicians to establish individualized caloric targets for weight loss, maintenance, or gain. Standard weight loss recommendations typically create a caloric deficit of 500 to 750 kcal/day below total daily energy expenditure (which includes REE plus activity and dietary thermogenesis), targeting approximately 1 to 1.5 pounds of weight loss per week, as recommended by the CDC and American Heart Association.
Critical care and hospitalized patients benefit significantly from REE assessment. Illness, trauma, surgery, and sepsis alter metabolic demands substantially—sometimes increasing REE by 20 to 50 percent above predicted values. Indirect calorimetry, which measures oxygen consumption and carbon dioxide production to calculate REE, helps guide nutritional support in intensive care units. Underfeeding critically ill patients can impair wound healing, immune function, and recovery, while overfeeding increases complications including hyperglycemia, hepatic steatosis, and difficulty weaning from mechanical ventilation.
In endocrine disorders, REE measurements may provide supportive information but do not replace laboratory evaluation. Unexplained weight changes despite appropriate dietary intake should prompt comprehensive evaluation, including thyroid function testing and appropriate referrals. REE measurements may help monitor treatment response in established endocrine conditions but are not routinely used for initial diagnosis of conditions like metabolic syndrome or polycystic ovary syndrome.
Bariatric surgery patients represent another population where REE monitoring proves valuable. Post-surgical metabolic changes, including decreased REE due to reduced body mass and potential metabolic adaptation, require ongoing nutritional adjustment. Serial REE measurements help optimize protein and caloric intake during rapid weight loss phases and subsequent weight maintenance.
Additionally, REE assessment supports sports nutrition planning for athletes requiring precise energy balance, eating disorder treatment where metabolic suppression is common, and geriatric care where age-related metabolic decline affects nutritional requirements.
Red flags that may warrant medical evaluation include unintentional weight loss of 5% or more over 6-12 months, rapid unexplained weight gain, fatigue, heat or cold intolerance, heart palpitations, tremor, constipation, or hair loss. These symptoms should prompt consultation with a healthcare provider, who may refer to an endocrinologist or registered dietitian nutritionist (RDN) for specialized care.
Resting energy expenditure can be determined through direct measurement or estimation using predictive equations, each approach having distinct advantages and limitations. Indirect calorimetry represents the clinical reference standard for measuring REE. This technique uses a metabolic cart or handheld device to measure oxygen consumption (VO₂) and carbon dioxide production (VCO₂) while the patient rests quietly. The Weir equation then converts these gas exchange measurements into energy expenditure: REE (kcal/day) = [3.9(VO₂) + 1.1(VCO₂)] × 1.44, where VO₂ and VCO₂ are measured in mL/min. This method provides accuracy within 5 to 10 percent under proper conditions but requires specialized equipment, trained personnel, and patient cooperation for 15 to 30 minutes of quiet rest.
Predictive equations offer practical alternatives when indirect calorimetry is unavailable. The Mifflin-St Jeor equation is currently recommended by the Academy of Nutrition and Dietetics as the most accurate for general populations:
Men: REE = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5
Women: REE = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161
The Harris-Benedict equation (revised in 1984) remains widely used despite slightly lower accuracy:
Men: REE = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)
Women: REE = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)
For obese patients (BMI ≥30 kg/m²), the accuracy of predictive equations varies by individual and degree of obesity. In some clinical settings, particularly for hospitalized patients, practitioners may use adjusted body weight: ideal body weight + 0.4(actual weight - ideal weight), though evidence supporting specific adjustment factors is limited and context-dependent.
Other equations may be preferred in specific populations—the Owen equations for older adults, the Cunningham equation for athletes, and the Penn State equation for mechanically ventilated patients.
Limitations of predictive equations include potential errors of 10 to 20 percent in individuals, particularly those with altered body composition, metabolic disorders, or extreme ages. Equations perform best for populations similar to those in which they were developed—generally healthy adults of normal weight. Clinicians should interpret calculated REE values cautiously and consider direct measurement when precision is clinically critical, such as in critically ill patients, those with unexplained weight changes despite appropriate interventions, or individuals with suspected metabolic disorders.
BMR (basal metabolic rate) is measured under highly standardized conditions after overnight fasting and immediately upon waking, while REE (resting energy expenditure) uses slightly less restrictive conditions requiring 15-30 minutes of quiet rest. RMR values are typically about 10% higher than BMR due to these measurement differences, though the terms are often used interchangeably in clinical practice.
Consumer fitness devices and apps that estimate resting calories typically have error margins of 10-20% compared to clinical measurements using indirect calorimetry. For precise metabolic assessment, especially when managing medical conditions or unexplained weight changes, clinical measurement or validated predictive equations are preferred.
Consult a healthcare provider if you experience unintentional weight loss of 5% or more over 6-12 months, rapid unexplained weight gain, persistent fatigue, heat or cold intolerance, heart palpitations, or other concerning symptoms. Your provider may order thyroid function tests and refer you to an endocrinologist or registered dietitian nutritionist for specialized evaluation.
All medical content on this blog is created using reputable, evidence-based sources and is regularly reviewed for accuracy and relevance. While we strive to keep our content current with the latest research and clinical guidelines, it is intended for general informational purposes only.
This content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a licensed healthcare provider with any medical questions or concerns. Use of this information is at your own risk, and we are not liable for any outcomes resulting from its use.
