Ayurveda considers AGNI as the major component which is responsible for digestion. One must suppose to have food when he is hungry (i.e. agni is strong)

It is said that agni is the stronger in early time after 3 hours of sunrise. So one must have its lunch at time of breakfast only.

It is always recommended to replace breakfast & meals as shown in the figure.

So Preferrable time for lunch is 10am-11am & dinner is suppose to be by 7:30pm