Cooking for someone on weight loss medication usually starts with the wrong assumption: that it means cooking two separate dinners every night. That's not sustainable for most households, and it isn't necessary. A more workable approach is building one base meal for the table, then adjusting the plate rather than the menu for the person whose appetite has changed.
In practice, that looks like serving their protein first and in a smaller portion, going lighter on bread or starch-heavy sides on their plate specifically while everyone else has theirs as usual, and keeping the overall flavor profile on the milder end of what the family already eats rather than cooking a second menu from scratch. A sauce-based dinner works well for this kind of split, since the same pot can serve a smaller, softer portion to one person and a standard portion to everyone else without any extra cooking.
The harder part is often emotional rather than logistical: appetite on these medications is unpredictable meal to meal, and a portion that goes untouched isn't a reflection on the cooking. It helps to keep easy-to-reheat, protein-forward leftovers on hand for whenever appetite does show up, rather than treating every dinner as a one-shot event that has to land. It also helps to stop treating a full plate as the goal. Serving a smaller portion from the start, rather than a normal portion the person is expected to leave unfinished, removes a source of quiet pressure at the table for both people — nobody's tracking what didn't get eaten if what was served was already sized to fit.
This is general guidance — the right approach for a specific person is worth talking through with their care team, since appetite changes and dietary needs vary from person to person.