TDEE / Fat Loss / Diet Calculator
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Research & References

This page summarises the research base that informs the equations, walking estimator, macro systems, and projection logic inside TDEE-Calc.com. Last reviewed: 19. nov 2025.

Energy expenditure formulas

Our default basal metabolic rate uses the Mifflin–St Jeor equation before any multiplier is applied.[1] We continue to expose both the original Harris–Benedict constants and their Roza–Shizgal revision so users can match historical or clinical data sources.[2][3] Whenever body-fat inputs are available, the calculator pivots to the Katch–McArdle lean body mass line from McArdle et al., ensuring lean-centric BMR outputs for athletic or high-BF contexts.[4]

Activity & walking estimator

The job templates and logged-activity adjustments rely on the Compendium of Physical Activities MET dataset, which allows us to express exercise minutes as kcal/day additions.[5] Step brackets (<5k, 5–7k, 7–10k, 10–14k, 14k+) follow Tudor-Locke’s population analysis and are interpolated within each job band to deliver the baseline multiplier.[6] We separate NEAT adjustments from intentional exercise so the total multiplier remains inside the Levine-recommended 1.20–1.90 safety envelope.[7] Optional exercise intensity bumps (+0.01/+0.03/+0.05) mirror the American College of Sports Medicine guidelines for light, moderate, and vigorous training weeks.[8]

Goal timelines & projections

The goal engine references the NIH body-weight planner equations published by Hall et al. to map calorie adjustments into time-bound body mass changes.[9] For everyday use, we blend in the Thomas et al. simplification to keep projections responsive to user edits without solving the full differential model on each keystroke.[10] The UI guard-rails (weekly deficit ceilings, chart guidance, and lean mass warnings) are anchored to the clinical risk ranges summarised by Heymsfield & Wadden.[11]

Macro systems & diet styles

The PSMF preset, including its protein floors and time-boxed warnings, is taken directly from Lyle McDonald’s Rapid Fat Loss Handbook.[12] Protein ceilings and floors lean on the athlete-focused guidance from Phillips & Van Loon plus the Morton et al. meta-analysis to keep lean mass outcomes realistic for lifters toggling the weight-training flag.[13][14] Base carb and fat floors defer to the Institute of Medicine’s Acceptable Macronutrient Distribution Ranges so general wellness needs are met before diet-style tweaks.[15] The Keto HP and Standard Keto presets follow the field protocols published by Volek & Phinney, while the Zone option retains the 40/30/30 structure popularised by Barry Sears.[16][17]

References

  1. Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. doi:10.1093/ajcn/51.2.241
  2. Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington; 1919. Full text
  3. Roza AM, Shizgal HM. The Harris-Benedict equation reevaluated: resting energy requirements and the body cell mass. JPEN J Parenter Enteral Nutr. 1984;8(3):191–198. doi:10.1177/0148607184008003191
  4. McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. 8th ed. Wolters Kluwer; 2015.
  5. Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of Physical Activities: a second update of codes and MET values. Med Sci Sports Exerc. 2011;43(8):1575–1581. doi:10.1249/MSS.0b013e31821ece12
  6. Tudor-Locke C, Craig CL, Brown WJ, et al. How many steps/day are enough? For adults. Int J Behav Nutr Phys Act. 2011;8:79. doi:10.1186/1479-5868-8-79
  7. Levine JA. Non-exercise activity thermogenesis (NEAT). Best Pract Res Clin Endocrinol Metab. 2002;16(4):679–702. doi:10.1053/beem.2002.0227
  8. American College of Sports Medicine. ACSM’s Guidelines for Exercise Testing and Prescription. 11th ed. Wolters Kluwer; 2021.
  9. Hall KD, Sacks G, Chandramouli V, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826–837. doi:10.1016/S0140-6736(11)60812-X
  10. Thomas DM, Martin CK, Heymsfield SB, Redman LM, Schoeller DA. A simple model predicting individual weight change in humans. Am J Clin Nutr. 2013;98(3):554–561. doi:10.3945/ajcn.112.048033
  11. Heymsfield SB, Wadden TA. Mechanisms, pathophysiology, and management of obesity. N Engl J Med. 2017;376:254–266. doi:10.1056/NEJMra1514009
  12. McDonald L. The Rapid Fat Loss Handbook: A Scientific Approach to Crash Dieting. 5th ed. 2005. Publisher
  13. Phillips SM, Van Loon LJC. Dietary protein for athletes: from requirements to optimum adaptation. J Sports Sci. 2011;29(S1):S29–S38. doi:10.1080/02640414.2011.619204
  14. Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains. Br J Sports Med. 2018;52(6):376–384. doi:10.1136/bjsports-2017-097608
  15. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press; 2005. NAP
  16. Volek JS, Phinney SD. The Art and Science of Low Carbohydrate Performance. Beyond Obesity LLC; 2011.
  17. Sears B. The Zone: A Dietary Road Map. HarperCollins; 1995.