Resting energy expenditure (REE), or resting metabolic rate, is the number of calories your body burns at rest to maintain essential functions such as breathing, circulation, and temperature regulation. Understanding what constitutes a good resting energy level for weight loss begins with recognising that there is no single ideal value—rather, successful weight loss depends on creating an appropriate calorie deficit based on your individual REE and total daily energy expenditure. This article explains how to calculate your resting metabolic rate, establish safe calorie targets, and understand the factors that influence your metabolism to support sustainable weight management aligned with NHS and NICE guidance.

Understanding Resting Energy Expenditure and Weight Loss

Resting energy expenditure (REE), also known as resting metabolic rate (RMR), represents the number of calories (kcal) your body burns at complete rest to maintain essential physiological functions. These vital processes include breathing, circulation, cellular production, nutrient processing, and temperature regulation. REE is slightly higher than basal metabolic rate (BMR), which is measured under more strictly controlled conditions. REE typically accounts for 60–75% of total daily energy expenditure in most individuals, making it the largest component of calorie burning throughout the day.

Understanding your REE is fundamental to creating an effective weight loss strategy. When you consume fewer calories than your body expends—creating a calorie deficit—your body mobilises stored energy (primarily fat) to meet its energy requirements, resulting in weight loss. However, there is no single "good" resting energy value for weight loss; rather, the key is understanding your individual REE and using this as a baseline to establish appropriate calorie targets.

The relationship between REE and weight loss is not always straightforward. Metabolic adaptation can occur during prolonged calorie restriction, where the body reduces its energy expenditure as a protective mechanism. This phenomenon, sometimes called "adaptive thermogenesis", means that REE may decrease by more than would be predicted by weight loss alone. According to NHS guidance, sustainable weight loss should be gradual and supported by both dietary modification and increased physical activity, rather than relying solely on severe calorie restriction.

For most adults seeking weight loss, the focus should be on creating a moderate calorie deficit below total daily energy expenditure (TDEE), which includes REE plus calories burned through physical activity and food digestion. NICE recommends a multicomponent approach to weight management that addresses diet, physical activity, and behavioural change, rather than focusing exclusively on resting metabolic rate.

How to Calculate Your Resting Metabolic Rate

Several validated equations can estimate your resting metabolic rate, with the Mifflin-St Jeor equation being one of the most accurate for the general population. This formula calculates REE based on weight, height, age, and biological sex:

For men: REE = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5

For women: REE = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

For example, a 40-year-old woman weighing 75 kg and measuring 165 cm tall would have an estimated REE of approximately 1,420 calories (kcal) per day. A 40-year-old man with the same weight and height would have an REE of approximately 1,586 calories (kcal) daily. These calculations provide a reasonable starting point for most individuals, though actual metabolic rates can vary between individuals.

In UK clinical practice, the Henry (Oxford) equations are commonly used. These equations consider weight, height, age and sex, and were developed using a large dataset including UK participants:

For men aged 30-60: REE = (8.4 × weight in kg) + (4.2 × height in cm) – (5.7 × age in years) + 877

For women aged 30-60: REE = (8.3 × weight in kg) + (4.1 × height in cm) – (3.1 × age in years) + 487

The Harris-Benedict equation (revised in 1984) and the Cunningham equation are alternatives. The Cunningham equation is particularly useful for individuals with known body composition, as it accounts for lean body mass: REE = 500 + (22 × lean body mass in kg). This approach recognises that muscle tissue is metabolically more active than fat tissue.

Whilst these equations provide useful estimates, indirect calorimetry remains the gold standard for measuring REE. This clinical test measures oxygen consumption and carbon dioxide production to calculate energy expenditure with greater precision. Some NHS specialist weight management services (Tier 3) and private clinics offer this assessment, though it is not routinely necessary for most people embarking on weight loss. For practical purposes, equation-based estimates combined with monitoring of actual weight loss progress over several weeks provide sufficient guidance for adjusting calorie intake appropriately.

Optimal Calorie Deficit for Safe Weight Loss

Creating an appropriate calorie deficit is essential for sustainable weight loss whilst preserving metabolic health and lean body mass. A weight loss rate of 0.5–1 kg per week is generally considered safe and sustainable. NICE typically advises an energy deficit of about 600 calories (kcal) per day as part of a multicomponent weight management programme.

It is crucial to understand that your calorie deficit should be calculated from your total daily energy expenditure (TDEE), not your resting metabolic rate alone. TDEE includes your REE plus calories burned through physical activity and the thermic effect of food (energy used to digest, absorb, and process nutrients). For sedentary individuals, TDEE is typically 1.2–1.4 times REE, whilst moderately active people may have a TDEE of 1.5–1.7 times REE.

The NHS 12-week weight loss plan typically suggests daily allowances of around 1,400 calories (kcal) for women and 1,900 calories (kcal) for men for weight loss. These are not absolute minimum thresholds but common targets that work for many people. Very low-calorie diets (VLCDs) providing 800 calories (kcal) or fewer should only be undertaken under healthcare professional supervision, typically for individuals with obesity (BMI ≥30) requiring rapid weight loss, and usually for a limited period (up to 12 weeks).

Excessively large calorie deficits can lead to several adverse effects, including loss of lean muscle mass, nutritional deficiencies, fatigue, hormonal disruption, and increased risk of gallstones. Furthermore, severe restriction often proves unsustainable, leading to weight regain. A moderate, consistent deficit combined with adequate protein intake (1.2–1.6 g per kg body weight) and resistance exercise helps preserve muscle mass during weight loss.

If you have existing health conditions, are pregnant or breastfeeding, have a history of eating disorders, or are taking medications, consult your GP before starting a weight loss programme. Your GP may refer you to local weight management services (Tier 2 or Tier 3) for additional support. If you experience persistent fatigue, dizziness, hair loss, or menstrual irregularities during calorie restriction, contact your GP for assessment.

Factors That Affect Your Resting Energy Expenditure

Numerous factors influence individual resting energy expenditure, explaining why two people of similar size may have different metabolic rates. Body composition is perhaps the most significant factor: muscle tissue requires more energy to maintain than fat tissue, meaning individuals with greater lean body mass typically have higher REE. This is why men generally have higher metabolic rates than women of similar weight, as they typically carry more muscle mass.

Age progressively affects REE, with metabolic rate typically declining by approximately 1–2% per decade after early adulthood. This reduction occurs primarily due to loss of lean muscle mass (sarcopenia) and changes in hormonal status. However, this decline is not inevitable—regular resistance training can help maintain muscle mass and metabolic rate throughout life.

Genetic factors contribute to individual variation in REE, with studies suggesting genetics may influence metabolic rate differences between individuals. However, genetic predisposition does not predetermine weight outcomes; lifestyle factors remain modifiable and influential.

Several medical conditions and medications can significantly impact REE. Hypothyroidism reduces metabolic rate, whilst hyperthyroidism increases it. The evidence regarding polycystic ovary syndrome (PCOS) and REE is mixed, with some studies suggesting potential metabolic differences. If you have PCOS and are concerned about weight management, discuss this with your GP. Medications including certain antidepressants, antipsychotics, corticosteroids, and beta-blockers can affect metabolism and weight. If you suspect a medication is affecting your weight, consult your GP but do not stop taking prescribed medicines without medical advice. You can report suspected side effects from medicines via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Previous dieting history can influence current metabolic rate through adaptive thermogenesis. Repeated cycles of weight loss and regain ("yo-yo dieting") may result in a lower REE than predicted. Additionally, sleep quality and duration affect metabolic hormones; chronic sleep deprivation is associated with reduced REE and altered appetite regulation. Most adults need 6–9 hours of quality sleep nightly to support metabolic health and weight management efforts.

Frequently Asked Questions