Our methodology
Last updated: May 2026
This page documents exactly how Cetona computes your caloric needs (BMR/TDEE) and keto macros. All formulas are scientifically validated and the sources are cited at the bottom of the page.
1. Basal metabolic rate (BMR)
Cetona uses the Mifflin-St Jeor equation (1990), considered the most accurate for healthy adults according to a 2005 American Dietetic Association meta-analysis. For men: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) + 5 For women: BMR = (10 × weight_kg) + (6.25 × height_cm) − (5 × age) − 161 This equation has an error margin of ±10% for 70% of the population, outperforming Harris-Benedict and Katch-McArdle for non-athletic profiles.
2. Total daily energy expenditure (TDEE)
TDEE multiplies your BMR by an activity factor: • Sedentary (little to no exercise): × 1.2 • Light activity (1-3 sessions/week): × 1.375 • Moderate activity (3-5 sessions/week): × 1.55 • Intense activity (6-7 sessions/week): × 1.725 These multipliers come from standard clinical nutrition guidelines and have been used by most macro calculators since the 1990s.
3. Goal adjustment
Once TDEE is established, Cetona applies a goal-specific multiplier: • Weight loss: −20% (moderate deficit, sustainable for 3-6 months) • Maintenance: 100% • Energy / mental clarity: −5% (mild deficit) • Athletic performance: +5 to +10% The deficit is capped to never drop below the safety floors (section 5).
4. Keto macro split
Cetona follows the standard ketogenic ratio: ~70-75% calories from fat, ~20-25% from protein, ≤5% from net carbs (typically 20-50g/day depending on the mode). Three modes are available: • Strict: 20g net carbs — induction and rapid ketosis • Lazy: 35g — more vegetable variety, more sustainable • Cyclical: 50g — for athletes with pre-workout carb needs Protein is computed in grams per kg of body mass (1.2 to 1.8 g/kg based on activity and age), with a higher floor for users 50+ to preserve muscle mass (sarcopenia prevention).
5. Safety floors
Cetona refuses to drop below 1500 kcal/day for men and 1200 kcal/day for women. These thresholds are based on Academy of Nutrition & Dietetics and EFSA positions. Below these floors, the risk of muscle loss, metabolic slowdown, micronutrient deficiencies, and hormonal disruption becomes clinically significant. If your TDEE × (1 − deficit) drops under the threshold, the app shows a warning and recommends increasing physical activity rather than cutting calories further.
6. Age and sex adjustments
From age 50, Cetona raises the protein target (1.2 → 1.5 g/kg) to slow sarcopenia. For post-menopausal women, the ratio is adjusted to account for muscle mass loss tied to hormonal changes. These adjustments are aligned with the PROT-AGE Study Group recommendations (2013) and the European Society for Clinical Nutrition and Metabolism (ESPEN).
7. AI meal plan generation
The recipes themselves are generated by Anthropic Claude (Sonnet 4.6). The model receives: user profile, macro targets, country, dietary restrictions, and forbidden ingredient list. Each plan is validated server-side by a Zod schema — if a day has out-of-target macros or contains a forbidden ingredient, it's regenerated or removed. No plan shown to the user contradicts their declared medical profile.
Scientific sources
- 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. PMID: 2305711.
- Frankenfield D, Roth-Yousey L, Compher C. "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults." Journal of the American Dietetic Association, 2005; 105(5):775-789. PMID: 15883556.
- European Food Safety Authority (EFSA), Scientific Opinion on Dietary Reference Values for energy (2013).
- Academy of Nutrition and Dietetics. Position paper on adult weight management.
Medical disclaimer
Cetona is not a medical service and does not replace consultation with a qualified healthcare professional. Plans are designed for healthy adults. If you are pregnant, breastfeeding, diabetic (type 1 or insulin-dependent type 2), on medication, or have a medical condition (cardiac, renal, hepatic, eating disorder), consult a physician or registered dietitian before starting a ketogenic diet.