Sources behind our numbers
Last updated
This is the full list of outside sources behind CalorTracker's food pages, calculators and AI estimates. Each entry says where it is used. If a source is not on this page, our numbers do not rely on it. For how the sources become the figures you see, read how we calculate; for how the writing is made, read the editorial policy.
Food data
- USDA FoodData Central
U.S. Department of Agriculture, public-domain (CC0) food composition database. The Foundation Foods, SR Legacy and FNDDS (Survey) datasets are downloaded and read by our import script. Used for: Every number on the food pages under /nutrition: calories, macros, other nutrients and household portions. The same values feed the recipe calorie calculator, the carbohydrate of each drink in the alcohol calorie calculator and the caffeine of each source in the caffeine calculator. - USDA FoodData Central search API
The same database, searched live by food name. Used for: Candidate matches when the app turns a photo, voice note or typed meal into a calorie estimate. - Open Food Facts
A crowd-sourced, open database of packaged foods. Used for: Second set of candidate matches, searched next to USDA, when the app estimates a meal. Not used for the food pages. - Herrmann SD, Willis EA, Ainsworth BE, et al. 2024 Adult Compendium of Physical Activities: a third update of the energy costs of human activities. J Sport Health Sci 2024;13(1):6-12.
The standard table of MET values (the energy cost of an activity relative to sitting quietly), one value per 5-digit activity code, kept at pacompendium.com. Used for: Every MET value on the calories-burned calculator and the /calories-burned pages, each stored with its code and the date it was read; and the six walking values the steps to calories calculator uses.
Reference values and bands
- FDA Daily Values, 21 CFR 101.9
The U.S. Food and Drug Administration's Daily Values for adults and children 4 years and older, as set in 21 CFR 101.9(c)(8)(iv) and 101.9(c)(9). Used for: The % Daily Value column on food pages. - CDC, Low-Energy-Dense Foods and Weight Management: Cutting Calories While Controlling Hunger (Research to Practice Series No. 5, 2008)
U.S. Centers for Disease Control and Prevention. The source of the energy-density bands: very low below 0.6 kcal per gram, low to 1.5, medium to 4, high above. Used for: The energy-density line in the diet-fit section of food pages. - Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378(9793):826-837.
A dynamic model showing that the 3,500 kcal per pound rule overstates long-run weight change, because a lighter body burns less. Used for: The caveat on every timeline in the energy and weight calculators, and on the calories to fat calculator: they are the earliest sensible estimate, not a forecast. - Centers for Disease Control and Prevention. Steps for Losing Weight (Healthy Weight and Growth).
CDC guidance that gradual, steady weight loss is about 1 to 2 pounds (0.5 to 0.9 kg) a week. Used for: The pace the weight loss, how long to lose weight and weight loss percentage calculators compare against. - Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press; 2005.
The Acceptable Macronutrient Distribution Ranges (carbohydrate 45 to 65% of calories, fat 20 to 35%), the carbohydrate Recommended Dietary Allowance of 130 g a day, and the Adequate Intake for fiber (14 g per 1,000 kcal, with fixed figures by age and sex). Used for: The carb, fat intake, fiber, cutting and bulking calculators, and the percentage ranges they show. - U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020.
The federal dietary guidance, including the advice to keep saturated fat under 10% of calories. Used for: The saturated fat ceiling on the fat intake calculator, and the 14 g of alcohol in a US standard drink on the alcohol calorie calculator. - Bueno NB, de Melo ISV, de Oliveira SL, da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. Br J Nutr 2013;110(7):1178-1187.
A meta-analysis that defines a very-low-carbohydrate ketogenic diet as under 50 g of carbohydrate a day. Used for: The three net carb limits (20, 30 and 50 g) the keto calculator offers, all inside that line. Used for the definition only, not for any claim about results. - 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 in muscle mass and strength in healthy adults. Br J Sports Med 2018;52(6):376-384.
A meta-analysis in which gains in muscle from extra protein level off at about 1.6 g per kg of body weight a day. Used for: The 1.6 to 2.2 g per kg protein range on the protein calculator, and the protein setting in the cutting, bulking and keto calculators. - Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. J Int Soc Sports Nutr 2018;15:10.
A review that suggests about 0.4 g of protein per kg of body weight per meal, across at least four meals, as a way to reach a daily protein range. Used for: The per-meal reference figure in the protein per meal section of the protein calculator. - FDA, 21 CFR 101.9(c)(6): Nutrition labeling of food, total carbohydrate.
The US regulation under which total carbohydrate on a Nutrition Facts label includes dietary fiber, sugars and (where declared) sugar alcohols. It defines no net carbs figure. Used for: The net carbs calculator: why fiber and sugar alcohols can be subtracted from the total, and why the sugar alcohol share is the reader's choice. - Ashwell M, Gibson S. A proposal for a primary screening tool: 'Keep your waist circumference to less than half your height'. BMC Med 2014;12:207.
A paper proposing the waist-to-height ratio of 0.5 as a simple screening message. Used for: Why the waist-to-height ratio calculator shows half your height. The page applies no category. - World Health Organization. Waist circumference and waist-hip ratio: report of a WHO expert consultation, Geneva, 8-11 December 2008. Geneva: WHO; 2011. ISBN 9789241501491.
The report of an expert consultation on waist circumference and waist-hip ratio, one objective of which was to define potential cut-off points for public health action. Used for: The waist-to-hip ratio calculator links it and applies no cut-off. - Tudor-Locke C, Aguiar EJ, Han H, et al. Walking cadence (steps/min) and intensity in 21-40 year olds: CADENCE-adults. Int J Behav Nutr Phys Act 2019;16:8.
A treadmill study of 76 adults that proposed about 100 steps a minute as the cadence of moderate-intensity walking (3 METs) and 130 steps a minute as vigorous (6 METs). Used for: The reference point beside the cadence the steps to calories calculator shows. It is not used to compute anything. - Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: The National Academies Press; 2005.
The Adequate Intake of total water (drinks and food together): 3.7 litres a day for men and 2.7 litres for women aged 19 to 30. The report puts about a fifth of total water intake as coming from food. Used for: The comparison line on each water-by-weight page. The water calculator's own rule of thumb (33 ml per kg) is not from this report. - Lichtman SW, Pisarska K, Berman ER, et al. Discrepancy between self-reported and actual caloric intake and exercise in obese subjects. N Engl J Med 1992;327(27):1893-1898.
A study in which subjects who reported eating little and not losing weight were found to under-report their intake and over-report their exercise. Used for: The blog posts that say people tend to under-record what they eat: the calorie-targets, accuracy, plateau and eating-out posts. - Shcherbina A, Mattsson CM, Waggott D, et al. Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort. J Pers Med 2017;7(2):3.
A study of seven wrist-worn devices, finding heart rate readings were close but energy expenditure estimates had large errors. Used for: The blog posts that tell readers to treat a watch's or app's calorie-burn figure as an estimate: the workout logging, Health Connect and calorie-target posts. - Hall KD, Guo J. Obesity Energetics: Body Weight Regulation and the Effects of Diet Composition. Gastroenterology. 2017;152(7):1718-1727.
A review of controlled feeding studies on whether the macronutrient composition of a diet changes energy expenditure and body fat beyond its calories. Used for: The keto, low-carb and intermittent fasting pages, which say calories still decide the direction of weight. - Estruch R, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N Engl J Med. 2018;378(25):e34.
The published report of the PREDIMED trial, which describes the Mediterranean-style pattern its participants were asked to follow. Used for: The Mediterranean page's description of the pattern. No outcome from the trial is quoted. - World Health Organization. Healthy diet (fact sheet).
The WHO's description of a diet with plenty of vegetables, fruit, legumes, nuts and whole grains, and its general limits on free sugars, fats and salt. Used for: The Mediterranean, carnivore and pescatarian pages' general context. No figure is taken from it. - de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 2019;381(26):2541-2551.
A review of the evidence on intermittent fasting schedules, including how much of it comes from animal studies and short human trials. Used for: The intermittent fasting page's description of the common schedules and its caution about the evidence. - Burke LE, Wang J, Sevick MA. Self-monitoring in weight loss: a systematic review of the literature. J Am Diet Assoc. 2011;111(1):92-102.
A systematic review of studies that examined dietary self-monitoring, such as food diaries, in weight-loss programmes. Used for: The calorie counting and flexible dieting pages, which say tracking is associated with better results in the studies reviewed. - Manheimer EW, et al. Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis. Am J Clin Nutr. 2015;102(4):922-932.
A systematic review of randomised trials of paleolithic-style diets, noting the small number and short length of the trials. Used for: The paleo page's note that the trials are small and short. No outcome is quoted. - National Heart, Lung, and Blood Institute. DASH Eating Plan.
The institute's official description of the DASH eating plan, with daily servings by calorie level. Used for: The DASH page, which describes the pattern and sends readers to this page for the servings. No figure is copied from it. - National Institute of Diabetes and Digestive and Kidney Diseases. Celiac Disease.
An overview of coeliac disease and its dietary management from a US government institute. Used for: The gluten-free page's framing: diagnosis first, then diet. No figure is taken from it. - NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals.
What vitamin B12 does, which foods supply it and who has a low intake, including people who eat no animal products. Used for: The vegan, vegetarian, carnivore and pescatarian pages' nutrient notes. No amount is quoted. - NIH Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals.
Dietary sources of iron, how well plant and animal iron is absorbed, and the groups with higher needs. Used for: The vegan and vegetarian pages' nutrient notes. No amount is quoted. - NIH Office of Dietary Supplements. Calcium: Fact Sheet for Health Professionals.
Dietary sources of calcium, including fortified plant foods, and who needs particular attention to intake. Used for: The vegan page's nutrient notes. No amount is quoted. - NIH Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals.
Dietary sources of zinc and the effect of phytates in plant foods on how much is absorbed. Used for: The vegan page's nutrient notes. No amount is quoted. - European Food Safety Authority. Dietary Reference Values.
EFSA's overview of the dietary reference values for the European Union population, for energy, macronutrients and micronutrients. Used for: The budget eating page, as the European counterpart to the US guidance. No figure is taken from it. - U.S. Food and Drug Administration. Spilling the Beans: How Much Caffeine Is Too Much? Consumer Update.
FDA consumer guidance that 400 milligrams a day is an amount not generally associated with negative effects in healthy adults, and that people differ in how they respond. Used for: The 400 mg adult reference on the caffeine calculator. - EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the safety of caffeine. EFSA Journal 2015;13(5):4102.
The European Food Safety Authority's opinion that caffeine intakes of up to 400 mg a day, and single doses of up to 200 mg, do not raise safety concerns for healthy adults. It gives separate figures for pregnancy and for children, which this site does not use. Used for: The 400 mg a day and 200 mg single-dose references on the caffeine calculator, for healthy adults only. - World Health Organization. Guideline: Sugars intake for adults and children. Geneva: WHO; 2015. ISBN 9789241549028.
The WHO guideline that recommends free sugars be kept below 10% of total energy intake (strong recommendation) and suggests below 5% (conditional recommendation), and that defines free sugars. Used for: The two reference lines and the definition of free sugars on the sugar intake calculator. - FAO/WHO/UNU. Human energy requirements: report of a Joint FAO/WHO/UNU Expert Consultation, Rome, 17-24 October 2001. FAO Food and Nutrition Technical Report Series 1. Rome: FAO; 2004.
The expert consultation report that expresses energy in both kilocalories and kilojoules and converts them at 1 kcal = 4.184 kJ. Used for: The conversion factor of the kJ to kcal converter.
Calculator formulas
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241-247.
The Mifflin-St Jeor equation for resting energy expenditure (BMR). Used for: BMR, TDEE, calorie deficit and macro calculators, and the daily targets the app derives. - Wishnofsky M. Caloric equivalents of gained or lost weight. Am J Clin Nutr 1958;6(5):542-546.
The origin of the rule of thumb that a kilogram of body weight is worth about 7,700 kcal (about 3,500 kcal per pound). Used for: Turning a daily calorie change into a weekly change in weight in the calorie, weight loss, weight gain, calorie cycling and how long to lose weight calculators, and the calories to fat calculator. - Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm 1974;8:650-655.
The Devine ideal body weight formula. Used for: The ideal weight calculator. - Robinson JD, Lupkiewicz SM, Palenik L, Lopez LM, Ariet M. Determination of ideal body weight for drug dosage calculations. Am J Hosp Pharm 1983;40:1016-1019.
The Robinson ideal body weight formula. Used for: The ideal weight calculator. - Miller DR, Carlson JD, Lloyd BJ, Bauman SC. Determining ideal body weight (and mass). Am J Hosp Pharm 1983;40(10):1622-1625.
The Miller ideal body weight formula. Used for: The ideal weight calculator. - Hamwi GJ. Therapy: changing dietary concepts. In: Danowski TS, ed. Diabetes Mellitus: Diagnosis and Treatment, vol 1. American Diabetes Association, 1964.
The Hamwi ideal body weight formula. Used for: The ideal weight calculator. - Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr 2014;11:20.
A review that sets out contest-preparation nutrition in the order protein, then fat, then carbohydrate for the remaining calories. Used for: The order in which the cutting calculator divides calories. Its numbers are not used. - Iraki J, Fitschen P, Espinar S, Helms E. Nutrition recommendations for bodybuilders in the off-season: a narrative review. Sports 2019;7(7):154.
A review of off-season nutrition for bodybuilders, with the same order of protein, fat and then carbohydrate. Used for: The order in which the bulking calculator divides calories. Its numbers are not used. - Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol 1984;247(4 Pt 2):F632-F636.
The Boer lean body mass equations, from weight and height. Used for: The lean body mass calculator. - Hume R. Prediction of lean body mass from height and weight. J Clin Pathol 1966;19(4):389-391.
The Hume lean body mass equations, from weight and height. Used for: The lean body mass calculator. - Kouri EM, Pope HG, Katz DL, Oliva P. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med 1995;5(4):223-228.
Defines the fat-free mass index (fat-free mass in kg divided by height in m squared) and the version normalized to 1.8 m with a correction of 6.3 x (1.80 - height). Reports an upper limit of 25.0 among the 74 non-users in a sample of 157 male athletes, as preliminary findings. Used for: The FFMI calculator: the formula and the normalization. The 25.0 finding is quoted as a finding about that sample, never as a target or a category. - Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr 1991;65(2):105-114.
Prediction formulas for body fat from BMI, age and sex. For adults: body fat % = 1.20 x BMI + 0.23 x age - 10.8 x sex - 5.4, with sex 1 for men and 0 for women; the abstract reports a standard error of 4.1% body fat. Used for: The body fat from BMI section of the body fat calculator page. - Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS; American College of Sports Medicine. Position stand: exercise and fluid replacement. Med Sci Sports Exerc 2007;39(2):377-390.
The position stand that describes estimating an individual's sweat rate by weighing before and after exercise, names dehydration of more than 2% of body weight as the point to prevent, and notes wide differences between people in sweat rate and sweat electrolyte content. Used for: The sweat loss calculator's method (weight change plus fluid drunk minus urine) and its 2% reference note. No fluid or electrolyte amounts are taken from it. - Merrill AL, Watt BK. Energy value of foods: basis and derivation. Agriculture Handbook No. 74. Washington, DC: U.S. Department of Agriculture, Agricultural Research Service; 1973.
The USDA handbook that sets the Atwater general energy factors: 4 kcal per gram of protein and of carbohydrate, 9 for fat and 7 for alcohol. Used for: The 7 kcal per gram of alcohol and 4 kcal per gram of carbohydrate in the alcohol calorie calculator, the 4 kcal per gram of sugars in the sugar intake calculator.
What this list does not include
Some rules of thumb in the calculators are not tied to a single study, so there is nothing honest to cite: the protein ranges per kilogram, the water-intake rule, the macro split presets and the 7,700 kcal per kilogram used to turn a calorie deficit into weekly weight change. The how we calculate page states each one exactly as the code applies it.
We also do not list sources we have not used. A source joins this page in the same change that starts relying on it. To point out a mistake or a missing source, write to support@calortracker.com.