Raw vs. cooked food
The nutritional content of a food can change during preparation. The water content changes, but fat, protein and carbohydrates largely remain the same in grams – it is the weight that changes.
Weight change during preparation
When meat is cooked, it loses water and the weight goes down. When vegetables are boiled, they absorb water and the weight can increase. The nutrients (fat, protein, carbohydrate) do not always follow the weight proportionally – be aware of whether the declaration applies to raw or cooked weight.
Calculate on raw weight
The simplest and most accurate approach is to weigh ingredients in raw state and use nutritional values for raw product. Then you know exactly how much fat, protein and carbohydrate goes into the meal, regardless of how much water evaporates or is absorbed during preparation.
Fat that disappears
During cooking, some fat can run out of the meat and remain in the pan. If this fat is not part of the meal, it must be subtracted in the calculation. Weigh the fat that remains in the pan and subtract it from the original fat amount.