Food that is "low-carb" does not have a lot of carbohydrates.

Carbohydrates are a component of food. They include starches, which are found in foods like bread, rice, and potatoes; sugar; and fiber, which is found ln food like beans and apples. 

Some people eat food that is low in carbohydrates in order to lose weight.

You can also say that food is:

• low-fat
• low-calorie
• low-sugar
• low-sodium