Find a users most popular items

Question

Im using mongoDB and I need to find a users most popular entries. Im rather confused about how to do this. I believe I will need to use the aggregate method however im not too sure how. This is the user data

{
 "_id": ObjectId("58d26c3dd60bd36f40fa0498"),
 "user_id": ObjectId("587cd30bd338b90a6c18e58f"),
 "calories": 2000,
 "date": 20170222,
 "snacks": [
 {
  "nutrients": {
    "protein": 8.7,
    "carbs": 53.5,
    "fat": 34.8
  },
  "servings": 21,
  "calories": 495,
  "name": "Kinder Chocolate"
},
{
  "nutrients": {
    "protein": 7.5,
    "carbs": 56.5,
    "fat": 10.5
  },
  "servings": 23.8,
  "calories": 526,
  "name": "Dairy milk"
}
],
"dinner": [ ],
"lunch": [ ],
"breakfast": [ ]
}

Essentially I need to get the most popular items, for example if the user has added Kinder chocolate more than anything else it will be top of the list:

1."Kinder Chocolate"
2."Dairy milk"
3."Coca Cola"

Any help would be greatly appreciated.