Metabolism Review

Measurement

How human energy expenditure is measured

Metabolic rate is one of the most measurable things about you, and one of the most consistently misdescribed.

Updated 3 min read 40 citations Evidence strength 5/5

Blood sugar monitor with a test strip inserted into the port
Roy Zuo · CC BY-SA 4.0 · Wikimedia Commons

The four components

What your daily energy expenditure is made of
ComponentRoughlyHow variable
Resting metabolic rate60-70% of totalLargely determined by fat-free mass
Thermic effect of food~10% of intakeModestly higher on high-protein diets
Exercise activityHighly variableWhatever you deliberately do
Non-exercise activity (NEAT)The wildcardVaries severalfold between people and within a person

NEAT is where most of the genuine between-person variation lives — fidgeting, posture, spontaneous movement. It is also the component that falls quietly during a diet, which is a large part of what people experience as their metabolism "slowing".

Doubly labelled water

The reference method works by having you drink water labelled with stable isotopes of hydrogen and oxygen, then tracking their differential elimination. The gap between them reflects carbon dioxide production, and therefore energy expenditure, over one to two weeks of ordinary life. It is expensive and it is unarguable.

A systematic review of total energy expenditure measured this way in adults gives the current picture [2], and pooled analyses have produced estimates of both resting and total expenditure across populations [4][5]. Work in children with chronic disease shows the same methodology applied where prediction equations fail hardest [1].

Doubly labelled water as reference method

Why your fitness tracker disagrees with your app

A meta-analysis validated dietary assessment methods against doubly labelled water [3]. The finding is uncomfortable and consistent: people under-report intake substantially, and the under-reporting is larger in people with higher body weight. It is not deliberate deception — portion estimation is genuinely hard, and no food diary captures cooking oil accurately.

On the expenditure side, predictive equations were compared systematically in healthy adults and in athletes, and best-practice guidance exists for measuring resting metabolic rate properly. All of them are population averages with individual error bars of a few hundred kilocalories.

Energy availability, not just intake

A distinct concept matters for anyone training seriously: energy availability is intake minus exercise expenditure, relative to fat-free mass. Chronically low availability suppresses physiological function well before it looks like an eating disorder. A randomised trial found low energy availability reduced myofibrillar and sarcoplasmic protein synthesis, and nutrition education interventions have been trialled to address it.

Sleep interacts with all of this — sleep restriction changed weight-loss composition in a randomised trial, and sleep extension changed objectively measured energy intake [6]. More on our sleep evidence site.

Does diet composition change expenditure?

A little, and the size of the effect is genuinely contested. A prominent randomised trial examined energy expenditure during weight-loss maintenance on a low-carbohydrate diet [7] and reported a difference; the analysis has been argued over extensively since. The honest summary is that any effect is small relative to the difference between what people think they eat and what they eat.

Common questions

Do I have a slow metabolism?
Almost certainly not to a degree that explains a weight problem. Adjusted for body composition, resting metabolic rate varies much less between people than assumed — and measurement error in intake tracking is far larger.
Is a metabolic test at a gym worth it?
Indirect calorimetry can be accurate if done under proper conditions — fasted, rested, correctly calibrated. Most commercial testing does not meet them.
Does eating more often boost metabolism?
No. The thermic effect of food scales with how much you eat, not with how many sittings you divide it into.
Why did my weight loss stall?
Expenditure falls as mass falls, and intake drifts upward as vigilance decays. Both are ordinary. See metabolic adaptation.
Glucose meter and its accessories arranged on a flat surface
Roy Zuo · CC BY-SA 4.0 · Wikimedia Commons
The evidence behind this page A stacked bar showing the composition of the 40 publications cited on this page by study type. 10254meta-analysis (10)randomised trial (25)review (1)other (4)
40 publications, 1989–2026. That is a mix with both trials and syntheses in it, which is the position from which a claim about cause is reasonable. Source: this page’s own citation list, below.

References

Every citation below links to the original peer-reviewed record on PubMed or via DOI. Nothing here is a substitute for medical advice.

  1. Describing Energy Expenditure in Children with a Chronic Disease: A Systematic Review Luo B, Davidson ZE, O'Brien K, et al. · Advances in nutrition (Bethesda, Md.) · 2024 · Systematic review DOIPubMed 38432591Full text
  2. Total energy expenditure measured using doubly labeled water in adults with major chronic diseases: a systematic review Purcell SA, Craven SA, Limon-Miro AT, et al. · The American journal of clinical nutrition · 2024 · Systematic review DOIPubMed 39209153Full text
  3. Validity of dietary assessment methods compared with doubly labeled water in children: A systematic review and meta-analysis Mehranfar S, Jalilpiran Y, Jafari A, et al. · Obesity reviews : an official journal of the International Association for the Study of Obesity · 2024 · Meta-analysis DOIPubMed 38783784
  4. Estimates of Resting Energy Expenditure and Total Energy Expenditure Using Predictive Equations for Individuals After Bariatric Surgery: a Systematic Review with Meta-analysis Macena ML, Silva Júnior AE, Melo JM, et al. · Obesity surgery · 2023 · Meta-analysis DOIPubMed 37889369
  5. Accuracy of Resting Metabolic Rate Prediction Equations in Athletes: A Systematic Review with Meta-analysis O'Neill JER, Corish CA, Horner K · Sports medicine (Auckland, N.Z.) · 2023 · Meta-analysis DOIPubMed 37632665Full text
  6. Estimates of resting energy expenditure and total energy expenditure using predictive equations in adults with overweight and obesity: a systematic review with meta-analysis Macena ML, Paula DTDC, da Silva Júnior AE, et al. · Nutrition reviews · 2022 · Meta-analysis DOIPubMed 35551409
  7. Physical activity and incident type 2 diabetes mellitus: a systematic review and dose-response meta-analysis of prospective cohort studies Smith AD, Crippa A, Woodcock J, et al. · Diabetologia · 2016 · Meta-analysis DOIPubMed 27747395Full text
  8. Estimating activity energy expenditure: how valid are physical activity questionnaires? Neilson HK, Robson PJ, Friedenreich CM, et al. · The American journal of clinical nutrition · 2008 · Meta-analysis DOIPubMed 18258615
  9. Best practice methods to apply to measurement of resting metabolic rate in adults: a systematic review Compher C, Frankenfield D, Keim N, et al. · Journal of the American Dietetic Association · 2006 · Systematic review DOIPubMed 16720129
  10. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review Frankenfield D, Roth-Yousey L, Compher C · Journal of the American Dietetic Association · 2005 · Systematic review DOIPubMed 15883556
  11. Acute mild cold exposure with shivering reduces 24 h glucose levels in individuals with type 2 diabetes but not prediabetes Hashim D, Jörgensen JA, van de Weijer T, et al. · Diabetologia · 2026 · Randomised controlled trial DOIPubMed 42474505Full text
  12. Protein yogurt and whey protein produce comparable muscle gains, but divergent microbiome shifts during strength training in older adults Monsalves-Álvarez M, Calderón-Romero P, Hayes-Ortiz T, et al. · Scientific reports · 2026 · Randomised controlled trial DOIPubMed 42151371Full text
  13. Adaptive Thermogenesis After Hypocaloric Low-Carbohydrate Versus Low-Fat Diets in African American Women: A Secondary Analysis Lopez Torres SY, Gower BA, Garvey WT, et al. · Obesity (Silver Spring, Md.) · 2025 · Randomised controlled trial DOIPubMed 40931394Full text
  14. Measuring dietary intake among participants with a urea cycle disorder using standard diet records or a novel food photography app Sim E, Gregor A, MacLeod E, et al. · Molecular genetics and metabolism · 2025 · Randomised controlled trial DOIPubMed 41242089Full text
  15. The effect of nutrition education sessions on energy availability, body composition, eating attitude and sports nutrition knowledge in young female endurance athletes Tektunalı Akman C, Gönen Aydın C, Ersoy G · Frontiers in public health · 2024 · Randomised controlled trial DOIPubMed 38550312Full text
  16. Low energy availability reduces myofibrillar and sarcoplasmic muscle protein synthesis in trained females Oxfeldt M, Phillips SM, Andersen OE, et al. · The Journal of physiology · 2023 · Randomised controlled trial DOIPubMed 37329147
  17. Effect of Sleep Extension on Objectively Assessed Energy Intake Among Adults With Overweight in Real-life Settings: A Randomized Clinical Trial Tasali E, Wroblewski K, Kahn E, et al. · JAMA internal medicine · 2022 · Randomised controlled trial DOIPubMed 35129580Full text
  18. Energy balance in hypothalamic obesity in response to treatment with a once-weekly GLP-1 receptor agonist Shoemaker AH, Silver HJ, Buchowski M, et al. · International journal of obesity (2005) · 2022 · Randomised controlled trial DOIPubMed 34975146Full text
  19. Influence of sleep restriction on weight loss outcomes associated with caloric restriction Wang X, Sparks JR, Bowyer KP, et al. · Sleep · 2018 · Randomised controlled trial DOIPubMed 29438540Full text
  20. Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial Ebbeling CB, Feldman HA, Klein GL, et al. · BMJ (Clinical research ed.) · 2018 · Randomised controlled trial DOIPubMed 30429127Full text
  21. Does exercise training affect resting metabolic rate in adolescents with obesity? Alberga AS, Prud'homme D, Sigal RJ, et al. · Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme · 2017 · Randomised controlled trial DOIPubMed 27923279
  22. A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity Ravussin E, Redman LM, Rochon J, et al. · The journals of gerontology. Series A, Biological sciences and medical sciences · 2015 · Randomised controlled trial DOIPubMed 26187233Full text
  23. The influence of nighttime feeding of carbohydrate or protein combined with exercise training on appetite and cardiometabolic risk in young obese women Ormsbee MJ, Kinsey AW, Eddy WR, et al. · Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme · 2015 · Randomised controlled trial DOIPubMed 25409324
  24. Reading and listening to music increase resting energy expenditure during an indirect calorimetry test Snell B, Fullmer S, Eggett DL · Journal of the Academy of Nutrition and Dietetics · 2014 · Randomised controlled trial DOIPubMed 24794837
  25. Appetite control and biomarkers of satiety with vegetarian (soy) and meat-based high-protein diets for weight loss in obese men: a randomized crossover trial Neacsu M, Fyfe C, Horgan G, et al. · The American journal of clinical nutrition · 2014 · Randomised controlled trial DOIPubMed 24944057
  26. The doubly labeled water method produces highly reproducible longitudinal results in nutrition studies Wong WW, Roberts SB, Racette SB, et al. · The Journal of nutrition · 2014 · Randomised controlled trial DOIPubMed 24523488Full text
  27. Impact of energy restriction with or without resistance training on energy metabolism in overweight and obese postmenopausal women: a Montreal Ottawa New Emerging Team group study St-Onge M, Rabasa-Lhoret R, Strychar I, et al. · Menopause (New York, N.Y.) · 2013 · Randomised controlled trial DOIPubMed 22968252
  28. Caffeine intake, short bouts of physical activity, and energy expenditure: a double-blind randomized crossover trial Júdice PB, Matias CN, Santos DA, et al. · PloS one · 2013 · Randomised controlled trial DOIPubMed 23869233Full text
  29. Effect of dietary protein content on weight gain, energy expenditure, and body composition during overeating: a randomized controlled trial Bray GA, Smith SR, de Jonge L, et al. · JAMA · 2012 · Randomised controlled trial DOIPubMed 22215165Full text
  30. Validation of a pre-coded food record for infants and young children Gondolf UH, Tetens I, Hills AP, et al. · European journal of clinical nutrition · 2012 · Randomised controlled trial DOIPubMed 21829216
  31. Approaches for quantifying energy intake and %calorie restriction during calorie restriction interventions in humans: the multicenter CALERIE study Racette SB, Das SK, Bhapkar M, et al. · American journal of physiology. Endocrinology and metabolism · 2012 · Randomised controlled trial DOIPubMed 22127229Full text
  32. Calcium and dairy product modulation of lipid utilization and energy expenditure Teegarden D, White KM, Lyle RM, et al. · Obesity (Silver Spring, Md.) · 2008 · Randomised controlled trial DOIPubMed 18421269
  33. Training, muscle volume, and energy expenditure in nonobese American girls Eliakim A, Scheett T, Allmendinger N, et al. · Journal of applied physiology (Bethesda, Md. : 1985) · 2001 · Randomised controlled trial DOIPubMed 11133891
  34. Components of total energy expenditure in healthy young women are not affected after 14 days of feeding with medium-versus long-chain triglycerides Papamandjaris AA, White MD, Jones PJ · Obesity research · 1999 · Randomised controlled trial DOIPubMed 10348498
  35. Validity and reliability of reported dietary intake data Howat PM, Mohan R, Champagne C, et al. · Journal of the American Dietetic Association · 1994 · Randomised controlled trial DOIPubMed 8300993
  36. Use of the doubly labeled water method for measurement of energy expenditure, total body water, water intake, and metabolizable energy intake in humans and small animals Roberts SB · Canadian journal of physiology and pharmacology · 1989 · Review DOIPubMed 2692794
  37. Energy expenditure and obesity across the economic spectrum McGrosky A, Luke A, Arab L, et al. · Proceedings of the National Academy of Sciences of the United States of America · 2025 · Journal article DOIPubMed 40658837Full text
  38. Training volume and total energy expenditure of an Olympic and Ironman world champion: approaching the upper limits of human capabilities Dasa MS, Bu OA, Sandbakk Ø, et al. · Journal of applied physiology (Bethesda, Md. : 1985) · 2024 · Journal article DOIPubMed 39480269
  39. Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans Pontzer H, Durazo-Arvizu R, Dugas LR, et al. · Current biology : CB · 2016 · Journal article DOIPubMed 26832439Full text
  40. Compendium of physical activities: an update of activity codes and MET intensities Ainsworth BE, Haskell WL, Whitt MC, et al. · Medicine and science in sports and exercise · 2000 · Journal article DOIPubMed 10993420