Methodology & Scientific Sources

1. Calorie Calculation

Daily calorie targets are calculated using one of two BMR (Basal Metabolic Rate) formulas, selected automatically based on your profile:

• Mifflin-St Jeor (default): Estimates BMR from weight, height, age, and sex. Used when body fat percentage is not set.
• Katch-McArdle: Estimates BMR from lean body mass (BMR = 370 + 21.6 × LBM). Automatically used when body fat percentage is set in Macro Targets. More accurate for users with higher or lower than average body fat.

BMR is multiplied by a physical activity level (PAL) factor to estimate Total Daily Energy Expenditure (TDEE). Activity factors: Sedentary 1.2, Light 1.375, Moderate 1.55, Active 1.725, Very Active 1.9 — derived from Harris-Benedict activity categories and standardized by WHO/FAO/UNU.

When Apple Watch or smartwatch data is available, real measured energy expenditure replaces both formulas and activity factors for maximum accuracy.

Sources

• Mifflin MD et al. “A new predictive equation for resting energy expenditure in healthy individuals.” Am J Clin Nutr. 1990;51(2):241-7.
• Katch F, McArdle WD, Katch VL. Essentials of Exercise Physiology. Lippincott Williams & Wilkins, 2011.
• Harris JA, Benedict FG. “A biometric study of human basal metabolism.” Proc Natl Acad Sci. 1918;4(12):370-3.
• WHO/FAO/UNU. “Human energy requirements.” Food and Nutrition Technical Report Series 1, Rome, 2004.

2. Thermic Effect of Food (TEF)

TEF represents the energy your body uses to digest, absorb, and process food — approximately 5–15% of daily energy intake depending on macronutrient composition.

The app calculates TEF dynamically from your logged meals using per-macronutrient coefficients:

High-protein diets produce higher TEF because protein requires more energy to digest than carbohydrates or fat. On a ketogenic diet with high protein intake, TEF typically ranges from 8–12% of total intake, compared to ~10% for a standard mixed diet.

When Apple Watch or smartwatch data provides BMR and active calories, TEF is not included in those measurements — the app adds it explicitly. When using activity multipliers (PAL), TEF may be partially reflected in the multiplier, but the app calculates it separately for transparency and accuracy with varying macronutrient compositions.

Try our TEF Calculator to see how different macro ratios affect your thermic effect.

Sources

• Westerterp KR. “Diet induced thermogenesis.” Nutr Metab. 2004;1(1):5.
• Hall KD. “Predicting metabolic adaptation, body weight change, and energy intake in humans.” Am J Physiol Endocrinol Metab. 2010;298(3):E449-66.
• Blaxter KL. Energy Metabolism in Animals and Man. Cambridge Univ Press, 1989.

3. Macro Targets

Protein targets are set at 1.2–2.0 g per kg of body weight based on activity level, following the International Society of Sports Nutrition position stand. When body fat percentage is set and dynamic protein is enabled, the app uses lean body mass (LBM) instead of total weight for more accurate targets. For Build Muscle and Recomposition goals, protein is boosted by +0.2 g/kg (range 1.6–2.2 g/kg) to support muscle hypertrophy.

Carbohydrate targets are user-adjustable. Fat fills remaining calories after protein and carbs are set. Calorie values use standard Atwater factors: protein 4 kcal/g, carbohydrates 4 kcal/g, fat 9 kcal/g.

Sources

• Jager R et al. “International Society of Sports Nutrition Position Stand: protein and exercise.” J Int Soc Sports Nutr. 2017;14:20.
• Morton RW et al. “A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.” Br J Sports Med. 2018;52(6):376-384.
• Atwater WO, Bryant AP. “The chemical composition of American food materials.” USDA, 1906.

4. Carbohydrate Targets

The app supports a range of carbohydrate targets. For keto users (20–50g/day), the dashboard shows ketosis zone indicators based on published literature. For moderate or balanced carb targets (50–150g+), the app tracks intake relative to your chosen target without keto-specific messaging.

Actual ketosis depends on multiple factors including protein intake, energy balance, and individual metabolism — the app does not measure blood ketone levels.

Dynamic Carb Target (IOM AMDR)

When your carb target is above 50g and smartwatch workout data is available, the app can recommend a carb target based on your activity level and calorie budget, following the IOM Acceptable Macronutrient Distribution Ranges (2005), referenced by USDA Dietary Guidelines (2020–2025):

These values use the lower end of the IOM AMDR range (45–65%), appropriate for users in a caloric deficit. All macros stay within IOM AMDR ranges: Carbohydrates 45–65%, Protein 10–35%, Fat 20–35% of total calories.

Sources

• Volek JS, Phinney SD. The Art and Science of Low Carbohydrate Living. Beyond Obesity LLC, 2011.
• Paoli A et al. “Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets.” Eur J Clin Nutr. 2013;67(8):789-96.
• IOM. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
• USDA & HHS. Dietary Guidelines for Americans, 2020–2025. 2020.
• Thomas DT et al. “ACSM/AND/DC Joint Position: Nutrition and Athletic Performance.” Med Sci Sports Exerc. 2016;48(3):543-68.

5. Net Carbohydrates

Net carbs are calculated as total carbohydrates minus dietary fiber. Fiber consists of carbohydrate polymers that are not digested in the small intestine and do not produce a significant glycemic response.

Foods with less than 5g net carbs per 100g are classified as low-carb, consistent with staying within a 20–50g daily net carb budget for nutritional ketosis.

Sources

• IOM. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
• Slavin J. “Fiber and Prebiotics: Mechanisms and Health Benefits.” Nutrients. 2013;5(4):1417-35.

6. Weight Management

Weight loss projections use the commonly accepted estimate of 7,700 kcal per kg of body fat. The app recommends a maximum loss rate of 0.5–1.0 kg (1–2 lbs) per week, consistent with evidence-based guidelines for safe, sustainable weight loss. For muscle building goals, the recommended gain rate is 0.25–0.5 kg (0.5–1 lb) per week to maximize lean mass while minimizing fat gain.

Sources

• CDC. “Losing Weight: Getting Started.” Centers for Disease Control and Prevention.
• Slater GJ et al. “Is an Energy Surplus Required to Maximize Skeletal Muscle Hypertrophy Associated With Resistance Training.” Front Nutr. 2019;6:131.

7. Muscle Building (Caloric Surplus)

When your goal is set to Build Muscle, the app calculates a caloric surplus (calories above TDEE) to provide the energy needed for muscle protein synthesis.

The surplus is determined by your target weight, timeline, and weekly gain rate. The app caps the recommended gain rate at 0.5 kg/week (~550 kcal/day surplus). Most lean bulking protocols recommend 250–500 kcal/day — a slower gain rate within the app’s range minimizes unwanted fat gain.

Protein targets are boosted by +0.2 g/kg (range 1.6–2.2 g/kg) to support muscle hypertrophy. This is based on a meta-analysis of 49 studies showing that intakes above 1.6 g/kg/day maximize resistance training-induced muscle gains.

Sources

• Slater GJ et al. “Is an Energy Surplus Required to Maximize Skeletal Muscle Hypertrophy Associated With Resistance Training.” Front Nutr. 2019;6:131.
• Iraki J et al. “Nutrition Recommendations for Bodybuilders in the Off-Season.” J Int Soc Sports Nutr. 2019;16(1):38.
• Morton RW et al. “A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.” Br J Sports Med. 2018;52(6):376-384.

8. Body Recomposition

Body recomposition — simultaneously losing fat and gaining muscle — is possible when eating at maintenance calories with high protein intake and resistance training.

When your goal is set to Recomposition, the app sets calories at TDEE (no deficit or surplus) and boosts protein to 1.6–2.2 g/kg of body weight. No timeline is required because recomposition is a gradual process measured by body composition changes rather than scale weight.

Research suggests intakes of 2.0+ g/kg at maintenance calories combined with resistance training can produce measurable improvements in body composition even in trained individuals.

Sources

• Barakat C et al. “Body Recomposition: Can Trained Individuals Build Muscle and Lose Fat at the Same Time?” Strength Cond J. 2020;42(5):7-21.
• 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.

9. Body Mass Index (BMI)

BMI is calculated as weight (kg) divided by height (m) squared. Categories: Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese (≥30). BMI is a simple screening tool and does not account for muscle mass, body composition, age, sex, or ethnicity.

Sources

• WHO. “Body mass index — BMI.” World Health Organization.
• Keys A et al. “Indices of relative weight and obesity.” Int J Epidemiol. 2014;43(3):655-65.

10. Nutrition Targets

Reference values for fiber, sugar, and sodium are based on WHO dietary guidelines. Saturated fat follows WHO guidance (<10% of total calories) for standard diets.

For users on a ketogenic diet with carb targets below 50g, two adjustments are made:

• Sodium: Targets are increased to 3,000–5,000 mg/day because reduced insulin levels during carbohydrate restriction increase renal sodium excretion.
• Saturated fat: Allowance is increased to approximately 20% of total calories, as research shows that on well-formulated ketogenic diets, plasma saturated fatty acid levels decrease despite higher dietary intake due to increased fat oxidation.

Sources

• WHO. “Guideline: Sugars intake for adults and children.” 2015.
• WHO. “Guideline: Sodium intake for adults and children.” 2012.
• Phinney SD. “Ketogenic diets and physical performance.” Nutr Metab. 2004;1:2.
• DeFronzo RA. “The effect of insulin on renal sodium metabolism.” Diabetologia. 1981;21(3):165-71.
• Forsythe CE et al. “Limited effect of dietary saturated fat on plasma saturated fat in the context of a low carbohydrate diet.” Lipids. 2010;45(10):947-62.

Hydration

Daily water targets are calculated using an activity-scaled, lean-body-mass-aware formula. The per-kg multiplier scales with your activity level — because baseline water turnover rises with metabolic rate (Sawka 2007 / ACSM).

When body fat % is set, the formula uses lean body mass (LBM). When body fat % is not set, total body weight is used with a proportionally lower multiplier (27–39 ml/kg).

The LBM-based formula is more accurate because muscle tissue holds ~73% water while fat tissue holds only ~10–20%. Two people at the same weight but different body compositions have meaningfully different hydration needs (Wang 1999).

Target bonuses

• Ketogenic carb target (≤50g): +500 ml — strongest evidence is for the adaptation phase (first 1–4 weeks), when glycogen-bound water and sodium are excreted. Long-term, the bonus serves as an electrolyte buffer.
• Build Muscle / Recomposition goals: +250 ml — increased renal urea excretion from higher protein intake.

Total target is clamped between 2,000 and 5,000 ml.

Beverage Hydration Index (BHI)

Not all beverages hydrate equally. The AI estimates effective water content using the Beverage Hydration Index: milk ×1.5 (superior retention due to protein, fat, and electrolytes), beer ×0.9 (mild diuretic effect), coffee/tea/water ×1.0 (caffeine in moderate doses does not cause net dehydration). BHI adjustments are applied automatically during AI food recognition (Maughan 2016).

Sources

• Sawka MN et al. “American College of Sports Medicine Position Stand: Exercise and Fluid Replacement.” Med Sci Sports Exerc. 2007;39(2):377-90.
• Wang Z et al. “Hydration of fat-free body mass: review and critique of a classic body-composition constant.” Am J Clin Nutr. 1999;69(5):833-41.
• Phinney SD. “Ketogenic diets and physical performance.” Nutr Metab. 2004;1:2.
• Olsson KE, Saltin B. “Variation in Total Body Water with Muscle Glycogen Changes in Man.” Acta Physiol Scand. 1970;80(1):11-18.
• EFSA Panel on Dietetic Products, Nutrition and Allergies. “Scientific Opinion on Dietary Reference Values for water.” EFSA Journal. 2010;8(3):1459.
• Maughan RJ et al. “A randomized trial to assess the potential of different beverages to affect hydration status: development of a beverage hydration index.” Am J Clin Nutr. 2016;103(3):717-23.
• IOM. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press, 2004.

Activity &amp; Exercise Estimation

When you log a manual activity, calories burned are estimated using Metabolic Equivalent of Task (MET) values from the 2024 Adult Compendium of Physical Activities.

One MET equals 1 kcal/kg/hour — roughly the energy cost of sitting quietly. Examples: brisk walking = 4.3 METs, running (6 mph) = 9.8 METs, weight training = 5.0 METs.

When Apple Watch or smartwatch data is available, device-measured calories take priority. Manual activities are added on top of device measurements.

Sources

• Ainsworth BE et al. “2024 Adult Compendium of Physical Activities: A third update of the codes and MET values.” J Sport Health Sci. 2024.
• Jetté M et al. “Metabolic equivalents (METS) in exercise testing, exercise prescription, and evaluation of functional capacity.” Clin Cardiol. 1990;13(8):555-65.

11. Dietary Cholesterol

This app displays a 300mg daily cholesterol reference corresponding to the U.S. FDA Daily Value used on Nutrition Facts labels. It is shown for informational tracking only.

Current USDA Dietary Guidelines (2020–2025) do not set a specific daily cholesterol limit, and the American Heart Association recommends focusing on overall dietary patterns rather than cholesterol thresholds. Exceeding 300mg is flagged as informational, not as a warning.

Sources

• U.S. FDA. “Daily Value on the Nutrition and Supplement Facts Labels.” 21 CFR 101.9.
• Carson JAS et al. “Dietary Cholesterol and Cardiovascular Risk: A Science Advisory From the American Heart Association.” Circulation. 2020;141(3):e39-e53.
• USDA & HHS. Dietary Guidelines for Americans, 2020–2025. 2020.

12. Minimum Fat Intake

The app ensures a minimum daily fat target of 30g regardless of calorie deficit. Dietary fat is essential for absorption of fat-soluble vitamins (A, D, E, K) and for essential fatty acids that the body cannot synthesize.

Major dietary guidelines recommend fat intake of at least 20–35% of total energy. On a moderate deficit diet (1,500 kcal), 20% corresponds to approximately 33g of fat per day.

Sources

• IOM. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.
• EFSA. “Scientific Opinion on Dietary Reference Values for fats.” EFSA Journal. 2010;8(3):1461.

13. Food Data

The built-in food database uses nutrition values from USDA FoodData Central. Barcode scanning retrieves product data from the Open Food Facts database. AI-generated nutrition estimates from photos and meal descriptions are approximations and may vary from actual nutritional content.

Sources

• USDA FoodData Central. U.S. Department of Agriculture.
• Open Food Facts. Open database of food products (openfoodfacts.org).

Last updated: April 2026