Design Pattern to output separate different files from same input parameter

It seems that the only thing that changes between these three functions is a list of fields that get written. There are several ways you can represent "a field" (and thus a list of fields) in a program; one of the most convenient is doing so as a function that extracts this field's value from a Food instance.

The type of this representation would be Func<Food, object>, so with a List<Func<Food, object>> you are good to go.

public void WriteFoodData(IEnumerable<Food> foodList, IEnumerable<Func<Food, object>> valueProviders)
{
    using (StreamWriter sw = new StreamWriter("file.csv", false))
    {
        StringBuilder sb = new StringBuilder();
        foreach (Food f in foodList)
        {
            foreach (var provider in valueProviders)
            {
                sb.Append(provider(f).ToString());
            }
            sw.WriteLIne(sb.ToString());
            sb.Clear();
        }
    }
}

Now you can create a "list of fields" and use it to call this method:

var valueProviders = new List<Func<Food, object>>
{
    f => f.Field1,
    f => f.Field4,
    // etc
};

var foods = /* whatever */
WriteFoodData(foods, valueProviders);

I would remove the responsibility for formatting from your FoodService and inject it instead.

    public class FoodService()
    {
        public void WriteRecommendedFood(IList<Food> foodList, IFoodFormatter formatter)
        {
            using (StreamWriter sw = new StreamWriter("file.csv", false)
            {
                StringBuilder sb = new StringBuilder();
                foreach (Food f in foodList)
                {
                   sw.WriteLine(foodformatter.Format(f));
                }
                sw.Close();
            }
        }
    }

    interface IFoodFormatter
    {
        string Format(Food f);
    }

This whay you can create concrete formatters like CalculationFormatter and ElligableFoodsFormatter.