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. Meal plan generation
The recipes themselves are generated by Anthropic Claude. 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.