Answer may be:

After having food blood supply to the digestive increases helping organs responsible for digestion to function well. If we do any kind of exercise it will interfere with the digestive system causing cramps and an upset stomach. So exercises should be performed after two to three hours, however, sitting in Vajraasana is recommended in yoga which helps in the digestion of food.

It helps in curing acidity and gas formation and better absorption of nutrients along with other benefits.