Dynamic Body Weight Planner
Explore a simplified dynamic energy-balance scenario with adjustable feedback, an interactive weight curve and coefficient sensitivity.
Weight change scenarios inputs
Your weight-change scenario
71.17 kg · simplified model scenario
Day 365 · fixed intake change and feedback
Full result table
| Scenario day | Modelled kg | Change (kg) | Expenditure change (kcal/day) |
|---|---|---|---|
| 0 | 80 | 0 | 0 |
| 30.416667 | 78.864969 | -1.135031 | -24.970679 |
| 60.833333 | 77.824413 | -2.175587 | -47.862909 |
| 91.25 | 76.870469 | -3.129531 | -68.849691 |
| 121.666667 | 75.995926 | -4.004074 | -88.089625 |
| 152.083333 | 75.194177 | -4.805823 | -105.728111 |
| 182.5 | 74.459161 | -5.540839 | -121.898448 |
| 212.916667 | 73.785326 | -6.214674 | -136.722837 |
| 243.333333 | 73.167577 | -6.832423 | -150.31331 |
| 273.75 | 72.601247 | -7.398753 | -162.772571 |
| 304.166667 | 72.082056 | -7.917944 | -174.194778 |
| 334.583333 | 71.60608 | -8.39392 | -184.666251 |
| 365 | 71.169722 | -8.830278 | -194.266124 |
An educational adult scenario, not a validated individual weight-loss forecast. Fixed coefficients omit separate fat/lean compartments, glycogen, fluid, adaptive thermogenesis and adherence changes. Assumes stable initial weight. Not for children, pregnancy, breastfeeding or clinical nutrition planning. Curves below 40 kg or above 300 kg are rejected, not recommended.
Let’s work it out.
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How to use Dynamic Body Weight Planner
- Enter a starting adult weight that has been broadly stable and a sustained change from the intake maintaining that weight.
- Feedback changes expenditure as body weight changes, producing a curve that gradually flattens.
- The main curve uses your coefficients.
Worked example
At 80 kg, a sustained −300 kcal/day change with k = 22 and E = 7,700 gives 71.169722 kg at day 365. With no intake change, the model stays exactly at 80 kg.
Formula, accuracy & limitations
Simplified first-order model: dΔW/dt = (ΔI − kΔW)/E. For constant intake change ΔI, feedback k and tissue energy E: W(t) = W0 + (ΔI/k) × [1 − exp(−kt/E)]. Time constant = E/k days. This is not the full NIH Body Weight Planner model.
An educational adult scenario, not a validated individual weight-loss forecast. Fixed coefficients omit separate fat/lean compartments, glycogen, fluid, adaptive thermogenesis and adherence changes. Assumes stable initial weight. Not for children, pregnancy, breastfeeding or clinical nutrition planning. Curves below 40 kg or above 300 kg are rejected, not recommended.
These outputs use the stated model and your supplied inputs. A mathematically consistent model can still differ from personal measurements. Scenario curves and formula comparisons are not statistical confidence intervals.
Read the research and method reference ↗Define a change from a stable baseline
Enter a starting adult weight that has been broadly stable and a sustained change from the intake maintaining that weight. A value of −300 means 300 fewer calories than baseline, not an intake of 300 calories. This page does not calculate a recommended intake or infer your maintenance needs.
Inspect the simplified model assumptions
Feedback changes expenditure as body weight changes, producing a curve that gradually flattens. Effective tissue energy density sets the response speed. Both are constant, editable scenario coefficients. Research supports dynamic modelling, but the full NIH model includes more physiology; this implementation must not be presented as an equivalent validated forecast.
Compare sensitivity without a promised deadline
The main curve uses your coefficients. Companion curves change feedback by ±20% and label each assumption. Their spread is not a confidence interval. Water shifts, adherence, body composition and health can make actual readings differ substantially, so the tool reports a scenario rather than a guaranteed goal date.
Frequently asked questions
Is this the NIH Body Weight Planner?
This is a separate simplified first-order energy-balance model. The linked NIH research gives context for dynamic modelling; it does not validate this reduced implementation as the NIH planner.
Why does the curve flatten?
In this model, expenditure changes by k calories per day for each kilogram of change. That feedback progressively reduces the initial energy imbalance.
Why not divide the total deficit by 7,700?
That arithmetic assumes an unchanged energy imbalance. This scenario includes a fixed expenditure feedback term, although it still simplifies real physiology.
Do the alternative curves show my likely weight range?
They show chosen coefficient sensitivity only. They are not measured uncertainty bounds or a personal probability forecast.
