Clinical Nutrition Engine

1. Body Composition (Deurenberg et al., 1991)

When BF% is omitted, the engine uses the Deurenberg formula rather than Devine IBW. Devine scales linearly with height, systematically overestimating Lean Body Mass (LBM) in obese populations. Deurenberg isolates adipose tissue by factoring in age-related sarcopenic shifts and sexual dimorphism.

2. Basal Metabolism (Cunningham 1980 / Katch-McArdle)

The Cunningham equation (intercept 500, multiplier 22) is routed to athletes, accounting for highly metabolically active fat-free mass (organ hypertrophy, mitochondrial density). The Katch-McArdle is utilized for the general population.

3. Constrained TEE (Careau et al., 2021)

Exercise Activity Thermogenesis (EAT) is multiplied by 0.72. Careau demonstrated that ~28% of exercise calories are compensated by the down-regulation of basal systemic processes (e.g., immune and reproductive dampening), preventing classical deficit overestimation.

4. High-Protein TEF Algebra

Thermic Effect of Food (TEF) is calculated algebraically via an infinite geometric series: TDEE = (BMR+NEAT+EAT)/(1-0.15). This accurately yields true metabolic equilibrium for a high-protein diet, avoiding the error of applying flat TEF solely to BMR.

5. Adaptive Thermogenesis (Rosenbaum & Leibel, 2010)

The engine applies a 1% weekly penalty to TDEE, capped at 15%. This perfectly models the down-regulation of the hypothalamic-pituitary-thyroid (HPT) axis and Non-Exercise Activity Thermogenesis (NEAT) during prolonged hypocaloric states.

6. Deficit Limits (Alpert 2005 & ACSM)

The core clinical safeguard. The engine tests both the Seymour Alpert thermodynamic limit (adipose tissue yields max ~69 kcal/kg/day) and the ACSM limit (1% total body weight loss/week). It strictly binds the deficit to the lowest of these two constraints, preserving skeletal muscle in lean individuals and preventing cardiovascular stress in obese patients.

7. Substrate Partitioning (ISSN & IOM Guidelines)

• Protein: Scaled dynamically (2.4g/kg LBM for resistance, 1.8g/kg otherwise) to preserve nitrogen balance, strictly capped at 220g to prevent hepatic urea cycle overload.
• Fats: 1.0g/kg LBM baseline. Females receive a 1.15x modifier (Tarnopolsky et al.) accounting for estrogen-upregulated intramuscular triglyceride utilization.
• Carbohydrates: Remainder of calories, bounded by a hard 130g floor (Institute of Medicine RDA) to protect obligate CNS glucose demands and prevent starvation ketosis/neuroglycopenia.