If accuracy is a priority, always weigh food in the raw state when possible.
Most labels of animal products represent the raw state (even if frozen) unless otherwise stated.
As an example, on the chicken breast label, it’s likely to read something like the following:
Serving Size: 112g (4oz)
— Total Fat: ~2 grams (it varies depending on how lean the cut is)
— Carbohydrate: 0 grams
— Protein: ~22 grams
These macros pertain to the raw, thawed chicken breast. The same applies to other cuts of meat, like beef, pork, and fish.
Due to the differences in every cut of meat, which can be further influenced by how they’re raised, it’s impossible to know exactly what the macro composition is.
In fact, it’s impossible to know the exact macro composition of anything, as the calorie totals on packages and in the USDA databases are merely very good, educated estimates. Nothing is exactly 100 calories 100% of the time. Similarly, no steak will have exactly 22 grams of protein per serving. Sometimes it’s more or less due to the amount of fat within the serving.
Many will weigh out their portions cooked, but this can become problematic due to the way the food is prepared. If a food is steamed or baked, it’s going to retain more water than if it’s been cooked on an open flame where much of the water evaporates.
This is even more true for the person who loves meat burnt to a crisp because these meats are sure to weigh far less than the baked version.
Further, 100 grams of baked chicken will contain less protein than 100 grams of grilled blackened (dry) chicken. This illustrates that while you’re eating the same “post-cooked weight,” there will be a difference in calories, and this difference can accumulate over time.
Quite simply, the differences in cooked weight contribute to a substantial margin of error that could potentially throw off your tracking. For accuracy, always weigh your foods in the raw state when possible.