Whether a person is drowsy or refreshed after a meal has something to do with the protein in the food they eat  Most proteins contain an amino acid called tyrosine, which enters the brain to stimulate the formation of dopamine and neo-adrenaline  Birds and fish contain the most tyrosine, but not all foods containing tyrosine excite the brain
Meat contains tyrosine, but fat interferes with its absorption
Fish are rich in dopamines