A high protein breakfast brings down neurotransmitters which cause anxiety.
Protein takes longer to digest than carbohydrates, so the feeling of fullness lasts longer. Carbohydrates are sugars and starches.
Protein, whether animal or plant based, helps to keep his blood sugar levels stable for longer.
The lower the GI of foods, the more it will help to slow down digestion and absorption so that he is satisfied for longer and therefore less hungry. The GI or Glycaemic Index of foods is measured by glucose or foods which contain it. Proteins have a GI of 0.