In healthy people with regular feeding schedules during waking hours, the activity of specific genes in muscle tissue that manage glucose and fat metabolism follows a daily rhythm, and the timing of this activity matches changes in insulin levels in the blood.

In human skeletal muscle, the activity of genes involved in glucose uptake and energy production increases during the late afternoon, matching the time when insulin levels rise after eating. This pattern suggests a biological adjustment to anticipated nutrient intake.

During the overnight fast, the body increases the activity of a specific gene in muscle tissue (PDK4) at around 5:30 a.m., which aligns with low insulin and high fat levels in the blood, promoting the use of fat as a fuel source.

In healthy people who eat meals at consistent times each day, insulin levels in the blood rise to their highest point around 6:04 PM and reach their lowest point during the night while fasting, suggesting that when food is eaten has a stronger influence on insulin release than the body's internal clock.