Let's abolish dinner!
Being forced to fast due to circumstances is terrifying. But, in the best demonstration that more of a good thing is not necessarily better, we know that too much food also kills, albeit in a more prolonged way, and that it expiates the guilt of the owner of the brain that ate it.
After all, you don't die immediately after eating a daily McDonald's meal, but decades later from a heart attack. Convinced that establishing cause and effect requires immediate temporal association, the brain, clogged with fructose syrup and French fries, carries on.
Through mechanisms that are beginning to be understood, reducing food intake, also called calorie restriction but also known simply as “eating less,” is a sure way to extend healthy life. It works in humans, monkeys, worms, and flies. However, “eating less” is something everyone hates. Because moderation alone is not enough: for calorie restriction to work, you have to be perpetually hungry, consuming about 20% less than your usual calories.
Enter voluntary fasting as the savior of our appetites. When fasting, the body predominantly uses fat as an energy source: the love handles gradually disappear, the metabolism becomes healthier, and the brain becomes more alert. The next day, you can even indulge a little—as long as you respect the fast again the following day.
The problem is that intermittent fasting, where you eat for 12 hours and then don't eat for 12 hours, works very well for some people, but not for everyone. Why not?
A new study conducted at Columbia University in New York, USA, explains, tests variations, and even demonstrates how it works. Using laboratory fruit flies, which don't complain about their diet, don't hide candy under their mattresses, and don't raid the fridge in the middle of the night, Mimi Shirasu-Hiza and her team found that what matters is going into the night already in a fasting state, skipping dinner, and continuing that way until the next day.
The magic happens when fasting enhances something that already happens normally during the night, both in flies and in people: the process of cellular autophagy. The name is ugly and refers to self-destruction, but the process is positive for the body, and is more like cool recycling that actually reduces the pile of garbage that accumulates in cells as they live their lives.
Using those cool genetic manipulation tricks that cost money that the CNPq doesn't give and require peaceful reagents that Brazilian customs loves to hold up for a few months, Shirasu-Hiza and colleagues prove and confirm that what nighttime fasting does for flies is maximize the recycling of that junk that accumulates in our cells throughout our lives and, in ways not yet understood, ends up killing us.
Extracted from Suzana Herculano-Houzel (2025) Neuroscience of Everyday Life, originally published in Folha de São Paulo in November 2021