How To Get Drop Down List Value To Affect Multiple Cells

I have a rather simple problem (tough for me!). I am setting up a food log. I would like to have one column with common food items that I have in a drop down list. The list would be about 20+ things. The other columns would have relevant nutritional info such as calories, fat, carbs, etc.

The problem is how do I make the values in the other columns change depending on which food item I pick from the drop down list?

For example, if I choose bread from the list, how would I get the columns for carbs and calories to change accordingly.

The IF function would be too hard because I couldn't nest 20+ IF functions in the formula for each cell. Also, the drop down list would change as my diet changes, possibly reaching 50+ things.

Also, I would like to manually enter a serving size that would alter the nutritional values in each column (for example 0.5*Calories or Carbs).

It seems so simple in my head, but I can't figure out how to get it to work.