Methodology: every formula, every constant, every source

This page renders the live constants from the calculator code — the values below are imported from the same TypeScript module the calculators run, so the published methodology can't silently drift from what the tools actually compute. The engine is unit-tested against the bands these sources publish.

1. Protein target

Range: 1.2-1.6 g of protein per kg of reference weight per day. During intentional weight loss, protein intakes in this band consistently outperform lower intakes at preserving lean mass:

• Leidy HJ et al. "The role of protein in weight loss and maintenance." Am J Clin Nutr 2015;101(6):1320S-1329S.
• Kim JE et al. "Effects of dietary protein intake on body composition changes after weight loss in older adults." Nutr Rev 2016;74(3):210-24 (systematic review & meta-analysis).
• Morton RW 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):376-84 — benefits plateau ≈1.6 g/kg/day, the basis for our top-of-range recommendation with resistance training.
• Jäger R et al. ISSN Position Stand: protein and exercise. J Int Soc Sports Nutr 2017;14:20 — 1.4-2.0 g/kg/day for exercising individuals.
• Bauer J et al. PROT-AGE Study Group. J Am Med Dir Assoc 2013;14(8):542-59 — older adults ≥1.0-1.2 g/kg/day baseline; we emphasize the top of our range at age 65+.

Reference weight

Ideal body weight uses the Devine formula (Devine BJ. Drug Intell Clin Pharm 1974;8:650-5): 50 kg (men) / 45.5 kg (women) + 2.3 kg per inch over 5 ft. When current weight exceeds 120% of IBW, we apply g/kg targets to an adjusted body weight = IBW + 25% × (actual − IBW), the standard clinical-nutrition correction so protein scales with lean tissue rather than total mass (see Krenitsky J. "Adjusted body weight, pro: evidence to support the use of adjusted body weight in calculating calorie requirements." Nutr Clin Pract 2005;20(4):468-73). Below that threshold, actual weight is used directly.

Per-meal distribution

The daily target divides across 3-4 meals, following ~0.4 g/kg/meal (Schoenfeld BJ, Aragon AA. "How much protein can the body use in a single meal for muscle-building?" J Int Soc Sports Nutr 2018;15:10) with 25-30 g/meal as the practical anchor (Paddon-Jones D, Rasmussen BB. Curr Opin Clin Nutr Metab Care 2009;12(1):86-90). Food equivalents shown in the calculator are USDA FoodData Central values (fdc.nal.usda.gov), rounded:

2. Why muscle preservation is the goal

• STEP 1 DXA substudy (semaglutide 2.4 mg): lean body mass accounted for roughly 39% of total weight lost (fat mass −8.4 kg, lean mass −5.3 kg in the substudy population). Wilding JPH et al. N Engl J Med 2021;384:989-1002 (appendix).
• SURMOUNT-1 body-composition substudy (tirzepatide): ~75% of weight lost was fat mass, ~25% lean mass. Jastreboff AM et al. N Engl J Med 2022;387:205-16 (appendix).
• Context and countermeasures: Prado CM et al. "Muscle matters: the effects of medically induced weight loss on skeletal muscle." Lancet Diabetes Endocrinol 2024;12(11):785-7.

Two framing notes we hold ourselves to: proportional lean-mass loss in these trials is broadly comparable to other forms of rapid weight loss (it is not unique to the medications), and "lean mass" in DXA substudies includes water and organ tissue, not only skeletal muscle. The numbers justify taking preservation seriously — not panic.

3. Training minimums (planner)

• ≥2 resistance days/week, all major muscle groups: U.S. Physical Activity Guidelines for Americans, 2nd ed. (HHS, 2018) and WHO 2020 guidelines (Bull FC et al. Br J Sports Med 2020;54:1451-62).
• 1-3 sets × 8-12 reps, 7-10 exercises, for novice-to-intermediate trainees: ACSM position stand on progression models in resistance training. Med Sci Sports Exerc 2009;41(3):687-708.
• 150 min/week moderate aerobic activity: HHS 2018 / WHO 2020.

4. Energy math (plateau & maintenance calculator)

Resting metabolic rate uses Mifflin-St Jeor (Mifflin MD et al. Am J Clin Nutr 1990;51:241-7): 10W + 6.25H − 5A + 5 (men) / −161 (women) — the equation the Academy of Nutrition and Dietetics' systematic review rated most reliable for healthy adults (Frankenfield D et al. J Am Diet Assoc2005;105:775-89). TDEE multiplies RMR by the standard activity factors:

Deficit band: 500-750 kcal/day below expenditure, per the 2013 AHA/ACC/TOS guideline for the management of overweight and obesity (Jensen MD et al. Circulation 2014;129:S102-38). We clamp outputs at common clinical calorie floors (1200 kcal/day women / 1500 kcal/day men) and flag the case instead of printing lower numbers. Where measured metabolic adaptation exceeds equation predictions after large weight loss, we say so (Fothergill E et al. "Persistent metabolic adaptation 6 years after 'The Biggest Loser' competition." Obesity 2016;24:1612-9).

5. Label reference pages

The titration pages reproduce dose-escalation schedules from the current official U.S. prescribing information (linked on each page, verified 2026-08-05). They are reference material only. This site deliberately ships no interactive dosing tools and no reconstitution/compounding tools — that boundary is documented in the project README and enforced in what we build.

6. Known limitations

• Population equations. Mifflin-St Jeor carries ±10-20% individual error; Devine IBW is a 1974 pharmacy heuristic, not a body-composition measurement. We use them because they are the validated standards the cited guidance uses — and we show the uncertainty instead of hiding it.
• The protein evidence base is mostly from general caloric restriction and resistance-training populations, not GLP-1-specific RCTs — dedicated trials are still emerging. We extrapolate the established weight-loss standards and label that extrapolation honestly.
• People with kidney disease, who are pregnant, or with other protein-relevant conditions need individualized targets from their clinician — the calculators say this rather than pretending one formula fits everyone.
• LeanGLP is educational. Nothing here is a diagnosis, treatment, or a promise of results.