When I see a colleague who skipped lunch, they seem to lose focus and get annoyed a lot. At this time, it is often said, "I think I'm hungry and my energy is low." This is also the biggest factor that makes one hesitate when considering short-term fasting for health.
However, this seemingly plausible statement is actually a lie. According to a study published in the 《Psychological Bulletin》, there is no difference in cognitive function between adults who fast for more than 12 hours and those who have eaten a full meal.
A research team from Oakland University in the United States analyzed 71 studies involving 3,484 healthy adults to verify whether food intake actually affects brain function. Participants were comprehensively evaluated using 222 cognitive measurement indicators.
The study results showed that there was no difference between having a meal and not having one. Whether fasting for 12 hours or just having eaten, memory, attention, decision-making, and reaction time were the same. The researchers explained, "The results contradict the widespread assumption that fasting inherently impairs cognitive ability."
In this way, the brain endures well without food. During fasting, the body begins to break down fat into ketones, providing this as an alternative energy source to keep the brain alert. The researchers stated, "This metabolic flexibility is likely an evolutionary advantage that helps humans survive without food."
However, children were different from adults. Children showed a slight decrease in attention and memory during fasting. This aligns with previous research findings that breakfast is important for school performance. The researchers explained, "Children's brains are more sensitive to energy during the developmental process," while "adults show little to no change."
Interestingly, even adults experienced cognitive decline when exposed to food-related stimuli, such as seeing pictures of food or thinking about food-related words.
Short-term fasting can be beneficial for the body. The researchers stated, "Fasting promotes beneficial metabolic changes that activate the cell regeneration process and promote longevity."
The greatest effect of fasting comes from the way it changes internal processes. Fasting activates a type of cellular cleaner called autophagy, which removes and recycles damaged components. This is known to promote healthier aging.
Additionally, it improves insulin sensitivity, helping the body manage blood sugar more effectively and reducing the risk of diseases such as type 2 diabetes. The metabolic changes caused by fasting help reduce the risk of chronic diseases associated with overeating.
