Methodology & sources

Every LoseSize tool shows its math on its own page. This page collects the primary sources we build on. Where a value is a range in the literature, we state the range rather than pretending there's one magic number.

Weight & body metrics

• BMI: weight(kg) / height(m)², categories per CDC — About BMI and WHO obesity fact sheet. BMI has known limits (muscle vs fat) and every BMI tool on this site says so.
• BMR: Mifflin-St Jeor equation — Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-7. PubMed 2305711
• Body fat (Navy method): Hodgdon & Beckett. Prediction of percent body fat for US Navy men and women from body circumferences and heights. 1984. DTIC report
• Ideal weight formulas: Devine (1974), Robinson (1983), Miller (1983), Hamwi (1964) — published therapeutic dosage equations, presented as a range, never a target.
• Waist-to-hip ratio: WHO risk thresholds — WHO indicator registry.
• Safe rate of loss: 1–2 lb (0.5–1 kg) per week — CDC healthy weight loss. Calorie floors of 1,200 (women) / 1,500 (men) kcal/day per NIH guidance for evaluating weight-loss programs.

Nutrition data

• Generic foods: USDA FoodData Central (SR Legacy) — the US government's reference nutrient database.
• Packaged foods & barcodes: Open Food Facts — open database; products are crowd-maintained and values are shown as reported.
• Protein needs: 0.8 g/kg/day RDA (NIH/Institute of Medicine DRI), 1.2–2.0 g/kg/day range for active people per ISSN position stands — tools show the range, not a single number.
• Water: EFSA adequate intake ~2.0 L/day (women) / 2.5 L/day (men) from all beverages and food, adjusted for activity and climate — not "8 glasses".

Fitness math

• Race prediction: Riegel model (t2 = t1 × (d2/d1)^1.06) — Riegel PS. Athletic records and human endurance. American Scientist, 1981.
• One-rep max: Epley and Brzycki formulas, averaged; percentile context from published strength-standard surveys (Strength Level data).
• Walking energy: ~0.53 kcal per kg per km for level walking at moderate pace (Ainsworth Compendium of Physical Activities, walking 3.0 mph ≈ 3.5 METs).
• Exercise database: wger (open source, CC BY-SA).
• Weather: Open-Meteo. Our comfort score is a transparent additive model shown on the tool page — it is a convenience score, not a safety standard.

When these numbers are wrong

All of these tools estimate. Pregnancy, athletic body composition, medical conditions and medications can each make standard formulas misleading. Treat results as a starting conversation with a qualified professional — see our medical disclaimer.