Why protein is a minimum and the rest is a range
In our dish swap, protein can go up a lot and barely go down. That’s not arbitrary; it’s how coaches handle it in practice.
When we built dish swapping, we had to decide how much a replacement meal could deviate. The obvious choice was to use the same margin everywhere. That turned out to be wrong.
Kilocalories are a window. Too much is just as wrong for someone losing weight as too little is for someone gaining. Five per cent either way: at 2500 that’s 125 kcal, enough to notice and small enough to still find something.
Protein isn’t. Ask ten coaches what happens if a client gets twenty grams more protein than planned, and ten will shrug. Ask what happens with twenty grams less, and you get a story about preserving muscle during a deficit. In practice it’s a floor, not a target -- so that’s how we treat it: plenty of room up, barely any down.
Carbohydrates and fat are the room to manoeuvre. If kcal and protein are right, the difference has to come from somewhere. These two absorb it, so that’s where the margin should be widest.
Sugar is a ceiling. Staying under your goal isn’t a deviation but the point. A symmetrical range would reject a low-sugar dish, which nobody wants to have to explain.
The lesson is in the shape, not the numbers. Four values that look the same in a table all behave differently. Treating them with one generic margin is the easy choice, and it gives you a swap button that rejects exactly the right dishes.
And if nothing fits? Then we show what falls just outside, with the difference. An empty list is the worst outcome of a button you offer.
