Sources and editorial policy

Where our information comes from

Health information should be trustworthy. Here is how we build our tools, how we check them, and the research they are based on.

Last full review: 23 October 2026

Our editorial policy

• Only trusted sources. We use guidelines from health institutions (such as the WHO, NIH, CDC, USDA and EFSA) and peer-reviewed research in medical and nutrition journals.
• Published formulas only. Every calculator uses a published, widely used formula. We do not invent our own.
• Safety first. We never suggest fewer than 1,500 kcal a day for men or 1,200 kcal for women, we do not plan weight loss for people who are underweight, and our tools are for adults only.
• Plain language. We explain things in simple words and say clearly when something is an estimate.
• Regular reviews and corrections. We review our content at least once a year, and straight away when a guideline changes. If you find a mistake, please tell us, and we will check it and fix it quickly.
• Independent. Adverts pay for the site, but advertisers have no say in our content.
• Reviewed by: [Name and qualification of a registered dietitian or doctor who has reviewed the content. Leave this out until a real expert has reviewed it.]

Full list of sources

BMI

1. World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894, 2000.
2. WHO Expert Consultation. Appropriate body-mass index for Asian populations. The Lancet, 2004;363:157-163. doi.org/10.1016/S0140-6736(03)15268-3
3. National Heart, Lung, and Blood Institute (NIH). Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults, 1998. www.ncbi.nlm.nih.gov/books/NBK2003/
4. Centers for Disease Control and Prevention. About adult BMI. www.cdc.gov/bmi/adult-calculator/bmi-categories.html

Body fat

1. Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, Report 84-11, 1984.
2. Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. British Journal of Nutrition, 1991;65:105-114. doi.org/10.1079/BJN19910073
3. American Council on Exercise (ACE). Body fat percentage categories. www.acefitness.org/
4. Behnke AR, Wilmore JH. Evaluation and regulation of body build and composition. Prentice-Hall, 1974 (reference man and woman).
5. World Health Organization. Waist circumference and waist-hip ratio: report of a WHO expert consultation, 2008 (published 2011).

Calories and weight change

1. Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990;51(2):241-247. doi.org/10.1093/ajcn/51.2.241
2. FAO/WHO/UNU. Human energy requirements: report of a joint expert consultation, 2004 (activity levels). www.fao.org/4/y5686e/y5686e00.htm
3. Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet, 2011;378:826-837. doi.org/10.1016/S0140-6736(11)60812-X
4. National Heart, Lung, and Blood Institute (NIH). Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults, 1998. www.ncbi.nlm.nih.gov/books/NBK2003/

Macros, water and fibre

1. Institute of Medicine (National Academies). Dietary Reference Intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids, 2005. doi.org/10.17226/10490
2. Jäger R, et al. International Society of Sports Nutrition position stand: protein and exercise. Journal of the International Society of Sports Nutrition, 2017;14:20. doi.org/10.1186/s12970-017-0177-8
3. U.S. Department of Agriculture and HHS. Dietary Guidelines for Americans, 2020-2025. www.dietaryguidelines.gov/
4. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific opinion on dietary reference values for water. EFSA Journal, 2010;8(3):1459. doi.org/10.2903/j.efsa.2010.1459
5. World Health Organization. Healthy diet fact sheet. www.who.int/news-room/fact-sheets/detail/healthy-diet

Food values

1. U.S. Department of Agriculture. FoodData Central (food energy and nutrient values). fdc.nal.usda.gov/

Diets

1. Estruch R, et al. Primary prevention of cardiovascular disease with a Mediterranean diet supplemented with extra-virgin olive oil or nuts (PREDIMED). New England Journal of Medicine, 2018;378:e34. doi.org/10.1056/NEJMoa1800389
2. Appel LJ, et al. A clinical trial of the effects of dietary patterns on blood pressure (DASH). New England Journal of Medicine, 1997;336:1117-1124. doi.org/10.1056/NEJM199704173361601
3. Morris MC, et al. MIND diet associated with reduced incidence of Alzheimer's disease. Alzheimer's & Dementia, 2015;11(9):1007-1014. doi.org/10.1016/j.jalz.2014.11.009
4. Masood W, Annamaraju P, Khan Suheb MZ, Uppaluri KR. Ketogenic Diet. StatPearls, NCBI Bookshelf (updated regularly). www.ncbi.nlm.nih.gov/books/NBK499830/
5. Gardner CD, et al. Effect of low-fat vs low-carbohydrate diet on 12-month weight loss (DIETFITS). JAMA, 2018;319(7):667-679. doi.org/10.1001/jama.2018.0245
6. de Cabo R, Mattson MP. Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine, 2019;381:2541-2551. doi.org/10.1056/NEJMra1905136
7. Rolls BJ. The relationship between dietary energy density and energy intake. Physiology & Behavior, 2009;97(5):609-615. doi.org/10.1016/j.physbeh.2009.03.011
8. Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: vegetarian diets. Journal of the Academy of Nutrition and Dietetics, 2016;116(12):1970-1980. doi.org/10.1016/j.jand.2016.09.025
9. NIH Office of Dietary Supplements. Vitamin B12 fact sheet for health professionals. ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/