Nutrition Label lets you ask for popular nutritional information on almost any food you can think of. NEW UPDATE: ask, "Search Nutrition Label for a Big Mac," and get the full breakdown on nutrients including calories, fat, carbohydrates, and protein in almost any given food. Values are based on averages across different types of the requested food and its serving size.
So far, this is working nicely for me. I can access it in most cases using natural language and Alexa knows to access Nutrition Label. I would prefer to default from grams to oz. since I use imperial measures and having to convert is kind of a pain. But this is definitely the best nutritional info skill I've found so far.