Part of the Loopa iOS app guide.
The What-If simulator is the What If mode inside the Trends screen (see Trends on iOS). It projects your weight forward from your current plan and lets you drag the levers to see where different choices land. Nothing changes your plan until you say so. For the background math, see Weight forecast; for the app hub, Using the iOS app.
General wellness tracking, not medical advice.
Where it lives and how it opens
Tap What If on the Record | What If pills at the top of Trends. The simulator opens pre-set to your reality: your saved plan plus your last 30 measured days. If Trends was already showing the 30-day range, it reuses that data so opening the simulator costs no extra loading. A line up top reminds you: "PREVIEW · NOTHING IS SAVED UNTIL YOU CONFIRM".
The simulator needs your basics: sex, age, height and weight. If they're missing it shows a Profile Incomplete state pointing you to Health Settings; two minutes there opens it up.
Calibration to your measured last 30 days
The Your Last 30 Days card is what makes the forecast personal. It shows your measured intake, your estimated burn, what your saved plan promised, and the rate you're actually tracking (for example "Tracking −1.2 lb/wk"). From these it computes a personal burn offset (how much hotter or cooler your real metabolism runs than the textbook figure) and applies it to every projection below, telling you so in plain words.
Calibration needs a real signal: at least a 14-day weight trend plus seven logged food days. Without that, the card says it's using textbook math instead, and the offset is capped at ±500 kcal/day so one badly logged month can't bend the curve into fiction.
The projection curve
The Projection card opens with a verdict line: a goal date and how many weeks out, "AT GOAL · HOLD THE LINE", "BEYOND THE HORIZON · STEEPER LEVERS NEEDED", or, for a loss goal an intake never reaches, that the plan gains or holds instead. Below it:
- The this plan line, with a shaded ±20% band around it.
- A dashed current trajectory ghost line at your measured rate, drawn only when it meaningfully disagrees with the plan.
- A dashed goal rule at your target weight.
- Day-one tiles: BMR, Burn (marked "adj" when calibrated), Intake, and your weekly rate in lb or kg per week.
Projections stop at one year, past which the error bars swallow the line. If a pace would drop you below the safety floor (1,200 kcal for women, 1,500 for men), the simulator clamps to it and warns you to pick a gentler pace. If your profile notes pregnant or nursing, it locks to maintenance and models no deficit.
The levers
- Weight now and Goal weight steppers.
- Activity: Sedentary through Athlete.
- Pace: Hold, Slow, Moderate, Aggressive or Diabolical. You can also flip on Dial the kcal directly for a raw daily-calorie slider. The slider shows which pace preset it will save as, since the plan is stored as a pace, not a raw number.
- Diet & Macros: a diet style chip that applies a macro preset, plus protein (g/lb) and a carb cap you can nudge, with a live "P … C … F … at … kcal" preview.
Every lever change re-runs the projection instantly. There's no network round-trip, so the curve moves as you drag.
Make This My Plan
The Make This My Plan button appears only when something differs from your saved plan; when nothing has changed you see a "This is already your plan" badge. Tapping it opens a confirmation that lists exactly what would change (current weight, goal, activity, pace, diet/macros). Confirm and it saves the new plan; Today's Page then recalibrates around it.
What it does and doesn't promise
The curve iterates week by week, recomputing your burn from your falling weight rather than assuming a fixed rate, which keeps a months-long projection honest. It's calibrated to your own measured data. Even so it is a projection, not a guarantee: the ±20% band is there for a reason, estimated burn is an estimate, and the simulator refuses to model unsafe intakes.
