Health Information Citations

Last updated: April 26, 2026

FormFuel uses standard, peer-reviewed formulas to estimate body metrics and energy needs. The values shown in the app are estimates only, derived from the formulas below. They are not medical advice and should not replace professional clinical assessment.

Important: All metrics in FormFuel are estimates based on population-level formulas. Individual results vary based on factors not captured by these calculations (muscle mass, hydration, ethnicity, medical conditions). Always consult a healthcare provider before making decisions about your health, exercise, or nutrition.

Body Mass Index (BMI)

FormFuel calculates BMI using the standard metric formula:

BMI = weight (kg) / height (m)²

BMI categories follow the World Health Organization (WHO) classification:

Underweight: BMI < 18.5
Normal: 18.5 – 24.9
Overweight: 25.0 – 29.9
Obese: ≥ 30.0

Source: World Health Organization. Obesity: preventing and managing the global epidemic. WHO Technical Report Series 894. Geneva: World Health Organization; 2000. https://www.who.int/health-topics/obesity

Body Fat Percentage

FormFuel uses the Deurenberg formula to estimate body fat percentage from BMI, age, and sex:

Body Fat % = (1.20 × BMI) + (0.23 × age) − (10.8 × sex) − 5.4 where sex = 1 for male, 0 for female

Body fat ranges follow the American Council on Exercise (ACE) classification.

Source: 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(2):105–114. https://pubmed.ncbi.nlm.nih.gov/2043597/

Total Daily Energy Expenditure (TDEE)

FormFuel calculates TDEE from Basal Metabolic Rate (BMR) multiplied by an activity factor based on the user's stated goal:

BMR (male) = 88.36 + (13.4 × weight kg) + (4.8 × height cm) − (5.7 × age) BMR (female) = 447.6 + (9.2 × weight kg) + (3.1 × height cm) − (4.3 × age) TDEE = BMR × activity factor

Activity factors used: lose weight 1.375, build muscle 1.55, endurance 1.725, flexibility 1.375.

Sources:

Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism. Proceedings of the National Academy of Sciences. 1918;4(12):370–373.
Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. American Journal of Clinical Nutrition. 1984;40(1):168–182. https://pubmed.ncbi.nlm.nih.gov/6741850/

Lean Mass and Fat Mass

FormFuel's advanced analytics derive lean and fat mass from estimated body fat percentage:

Lean Mass = weight × (1 − body fat % / 100) Fat Mass = weight × (body fat % / 100)

Because body fat % is itself an estimate (Deurenberg formula above), lean and fat mass are estimates of estimates and should be interpreted as trends, not exact values.

Calorie Targets by Goal

FormFuel uses goal-based calorie targets aligned with the U.S. Dietary Guidelines:

Lose weight: ~1,800 kcal/day (a 500 kcal deficit yields ~1 lb/week loss)
Maintain / Endure: ~2,200 kcal/day
Build muscle: ~2,600 kcal/day (a 200–500 kcal surplus supports lean gains)

Source: U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020–2025. 9th Edition. December 2020. https://www.dietaryguidelines.gov

Calories Burned Estimation

Exercise calorie estimates use Metabolic Equivalent of Task (MET) values from the Compendium of Physical Activities:

Calories = MET × weight (kg) × duration (hours)

Source: Ainsworth BE, Haskell WL, Herrmann SD, et al. 2011 Compendium of Physical Activities: a second update of codes and MET values. Medicine & Science in Sports & Exercise. 2011;43(8):1575–1581. https://pubmed.ncbi.nlm.nih.gov/21681120/

Macronutrient Tracking

Food calorie and macro values in FormFuel's built-in food database are based on per-100-gram USDA reference values. When users log foods by weight, calories and macros scale linearly.

Source: U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. https://fdc.nal.usda.gov

AI Coach Disclaimer

FormFuel's AI Coach generates fitness, nutrition, and recovery suggestions using a large language model trained on general fitness literature. The AI does not have access to your medical history and cannot diagnose conditions or prescribe treatment. AI-generated advice should always be reviewed against guidance from a qualified medical or fitness professional. Do not follow AI suggestions if you have any pre-existing medical condition, are pregnant, or have any doubt about safety.

Reporting Errors

If you believe any health information in the app is inaccurate, please email support@formfuel.app. We treat reports about health-related accuracy with the highest priority.