How do I know if a food is high in fat, saturated fat, sugar or salt?

There are guidelines to tell you if a food is high in fat, saturated fat, salt or sugar or not. 

Total fat

High: more than 20g of fat per 100g

Low: 3g of fat or less per 100g

Sugars

High: more than 15g of total sugars per 100g 

Low: 5g of total sugars or less per 100g

Saturated fat

High: more than 5g of saturated fat per 100g 

Low: 1.5g of saturated fat or less per 100g 

Salt

High: more than 1.5g of salt per 100g (or 0.6g sodium) 

Low: 0.3g of salt or less per 100g (or 0.1g sodium)