I recently wrote to FreshDirect with this question:
The nutrition info for this item seems to be incorrect:
Using the widely-used formula to calculate calories based on grams of macronutrients:
fat X 9 + protein X 4 + carbs X 4 = total calories
The result is 298. However, the label says the total calories are 350.
Either the total calories or one of the macronutrients are incorrect.
Their support is always friendly but I didn’t have high hopes for much detail in the response. But then I got this response!
We our meals to a certified lab that analyzes the meals we create with very accurate results. The Atwater factors (4-4-9) are average factors used to estimate nutrition info, considering proximate values only (ie. carb (minus fiber), protein, fats, ash and water). For example, protein is always assigned a factor of 4, even though milk and milk products have a real protein factor of 4.27. Our lab analysis is much more accurate as it is an analysis of all food ingredients combined and is closer to the values one would get if they used the exact Atwater factors for each nutrient in each ingredient.
I found this to be a really interesting nugget of transparency into how nutrition info is calculated.
Also it touches on the question I asked here – it seems that the calories/gram does indeed vary from the standard 9 4 4.