1. A smart device for analyzing food items captured in two digital images, the smart device comprising: a display unit; a memory; and a processor coupled to the display unit and the memory and the processor configured to: display, on the display unit, a first digital image of a meal and a second digital image of the meal, wherein the first digital image of the meal is captured before the second digital image of the meal; determine a volume of each food item in the first digital image of the meal and a volume of the each food item in the second digital image of the meal by analyzing the first digital image and the second digital image using a digital image processing technique; and generate for displaying on the display unit an amount of intake for the meal based on a difference between the volume of the each food item in the first digital image and the volume of the each food item in the second digital image.