People usually get up around 7:00, so it is appropriate for them to have breakfast 20 to 30 minutes after get up when the appetite is the most exuberant. The 4-5 hour interval between breakfast and lunch is better which means we shall have breakfast during 7 am to 8 am. In addition, drinking some water before breakfast is more reasonable.
Some people eat breakfast very early to go to school or go to work. Some elderly are used to getting up early so they take breakfast at 5 or 6 am. Some studies reveal that it is not conducive to digestion and absorption to have breakfast too early.
During the night's sleep, most of the human body organs have taken a rest fully, but only the digestive organs don’t stop digesting and absorbing the food in the gastrointestinal tract, until they finish in the early morning. So the early breakfast will affect the rest of the gastrointestinal tract, and keep the digestive system in a long-term fatigue state resulting in the disturbance of gastrointestinal tract movement. Especially for the elderly with declined digestion-absorption and metabolic function, who are used to getting up early and have morning exercises, it is bound to affect gastrointestinal function that eating breakfast immediately after getting up as well as adverse for morning exercises.
After a night of sleep, a lot of water in human body is consumed from the urine, skin and breath, so in the morning the body is in a state of physiological water shortage. Therefore, drinking a cup of water instead of eating breakfast, will correct it, reduce blood viscosity, improve organ functions, and has great benefit to prevent some diseases.