Goals

Profile & Goals, under Settings, holds the few facts the budget needs and the goal it is working toward. The goal has two parts that are kept separate on purpose: the pace, which sets the calorie target, and the metric, which is the number progress is judged by.

Profile

Date of birth, sex, height and weight feed the resting energy equation. An activity level matters only until Apple Health has five days of measured movement, after which it feeds no arithmetic. The newest weigh-in keeps the profile weight current. Units are metric or imperial, your choice.

Direction and pace

Lose, maintain or gain.
Pace is either a preset rate or derived from a target weight and a target date. If the derived pace is faster than the safety limit, the plan is capped at the limit and the estimated arrival moves out accordingly; the profile shows the requested pace beside the applied one.
Estimated arrival is computed at the applied pace. It is not shown when the goal is maintenance, when nothing is moving, or when it would be more than five years out.
Protein follows the direction by default (0.8 g/kg to maintain, 1.2 to lose, 1.0 to gain), or a strength-training figure between 1.4 and 2.0 g/kg, or a number of grams you type.

How the pace becomes a calorie target, and the floors and caps on it, is on the Energy budget page.

What progress is measured against

Weight is the default and the only option until there is composition data. Once body composition readings from a connected scale span 21 days and the newest is no older than 14 days, you can judge the goal by body fat percent or by fat mass instead, with a target for that number.

This changes what progress and the projection are measured against, and when the goal counts as reached. The pace and the calorie target still come from total weight, because nobody can choose to lose fat specifically. The day you change the metric is marked on the chart, so a reader knows why the target line moved.

Projections

Weight is projected up to 60 days ahead from the plan's daily energy gap, at 7,700 kcal per kilogram. A deficit clamped by the safety floor projects the smaller rate.
Body fat or fat mass is projected along its own trend: a straight line through the readings, anchored at the newest, over the same 60 days. It is projected along the trend, not the calorie plan. It needs three weeks of readings and is withheld when the newest reading is stale; nothing is extrapolated from data that stopped.

Someone whose scale weight is flat while fat mass falls sees progress the weight chart cannot show. That is the point of the metric.

The export records the goal metric, its target, and when it last changed, so an outside reader can tell which number a stretch of history was being judged by.