Cutting timeline
Enter your measurements, activity level and goal to see an estimated calorie target and weight projection. You can compare the model with your logged weigh-ins; it cannot predict your individual response.
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Resting metabolic rate: Mifflin-St Jeor 1990. Maintenance: RMR × activity factor (1.2 to 1.9). Daily intake: maintenance minus 15, 20 or 25%, fixed from day one.
Projection: a port of the NIH Body Weight Planner model (Hall et al. 2011). Fat and lean mass, glycogen and its water, extracellular water and adaptive thermogenesis are integrated daily (Runge-Kutta 4) from the same equations and constants as the planner. On ten reference cases stored in the repository the port matches the planner's weight after the same number of days within 0.2%. The spec's acceptance bound is ±10%.
Fat versus lean: Forbes partition inside the model (the lean share of energy imbalance depends on current fat mass). The STEP 1 trial's 62% fat / 38% lean figure is shown as a literature reference, not used in the arithmetic. Protein floor: the same rule as the protein-per-meal tool.
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241-247.
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826-837. - the model behind the NIH Body Weight Planner
- NIH Body Weight Planner - reference implementation used for the 10-case benchmark
- Wilding JPH et al. STEP 1 trial, body-composition substudy. N Engl J Med 2021;384:989-1002. - 62% fat / 38% lean split, literature reference only
- Obesity Pillars 2025 protein review (PMC12264624) and Morton 2018 BJSM - protein floor
Straight answers
How is maintenance calculated?+
Resting rate from Mifflin-St Jeor (1990): 10 × weight kg + 6.25 × height cm - 5 × age, plus 5 for men or minus 161 for women. Multiplied by an activity factor from 1.2 (desk, no training) to 1.9 (physical job plus hard training). Formula maintenance is a starting guess; weigh-ins over time can help you compare the estimate with your logged trend.
What does the range mean?+
The same plan run at 85% and 115% adherence to the deficit. These are illustrative scenarios, not a confidence interval or a prediction of your individual response.
Is the daily target safe?+
The tool caps the deficit at 25% of maintenance and shows a protein floor. It does not know your medical history. If you are under medical care or on medication that affects appetite, your clinician sets the numbers, not a calculator.
Why does the projection slow down over time?+
Because the model is not 7,700 kcal per kilo forever. As weight drops, resting rate and the cost of moving drop with it, and the body adapts a little on top (thermogenesis). The projection integrates that day by day, the same way the NIH Body Weight Planner does, so week 20 is slower than week 2.
Where does the fat versus lean split come from?+
From the model's own partition rule (Forbes): the leaner you are, the larger the lean share of any loss. That is why the split changes with your starting body fat instead of being one fixed number. The STEP 1 figure of 62% fat is shown as a literature reference only.