The body operates on a 24-hour circadian rhythm, which can cause a slight dip in alertness and energy levels in the afternoon, leading to drowsiness, fatigue, and difficulty concentrating.

Changes in circadian rhythm

According to Verywell Health, alertness levels fluctuate throughout the day due to the influence of the circadian rhythm. Melatonin, a hormone that helps regulate the sleep-wake cycle, typically increases in the evening to signal the body to prepare for rest. As melatonin rises, feelings of sleepiness emerge, reducing alertness and concentration.

Blood sugar changes after lunch

The brain may be less alert in the afternoon due to changes in blood sugar after a meal. A lunch rich in refined carbohydrates or sugary drinks can cause blood sugar to spike rapidly and then drop, leading to drowsiness, fatigue, and difficulty concentrating in some individuals.

It is advisable to prioritize a balanced lunch with protein, vegetables, fiber, and healthy fats. Limiting refined carbohydrates and sugary drinks can help maintain more stable energy levels throughout the afternoon.

Oily fried foods can easily increase blood sugar levels. Photo: Anh Chi

Stress

Work or study-related stress can elevate the hormones cortisol and adrenaline, keeping the body in a state of vigilance, increasing heart rate, and consuming more energy. If prolonged, this condition can lead to muscle tension, affecting sleep and the body's recovery process.

As pressure accumulates throughout the day, individuals can easily experience mental fatigue, a heavy head sensation, reduced alertness, and difficulty concentrating. When stress is prolonged, the body finds it hard to transition from a vigilant state to rest, so feelings of exhaustion may be more pronounced after many hours of work.

Fatigue after many hours of work

The brain must continuously receive and process information, make decisions, and control movement, posture, and emotions throughout the day. When required to focus for extended periods without adequate rest, the brain can enter a state of fatigue, leading to reduced memory and information processing capabilities.

According to WebMD, mental fatigue differs from muscle fatigue after physical exertion, primarily manifesting as feelings of exhaustion, lack of energy, difficulty concentrating, or reduced motivation. This condition can be more evident in the afternoon after many hours of studying or working.

Anh Chi (compiled)