Overeating not only harms physical health, but also toxic for spiritual health
Overeating is one of the most important causes that hinder intellectual and spiritual growth both from the scientific point of view and from the perspective of Islamic teachings.
Eating too much food causes weight gain and associated health problems, obviously, but it causes spiritual harm as well. Too much food hardens the heart, dulls the mind, increases drowsiness, and makes it even more difficult to control one’s lusts and desires.
For this reason, the Sunnah regarding day-to-day eating is to only eat what is necessary to maintain optimal health and energy. At most, one should fill their stomach with no more than a third of food and a third of water, and leave the remaining third empty. One should not be in the habit of completely filling his or her stomach every day.
Habitually eating too much food on a day-to-day basis is a manifestation of one’s inability to control their desires and their attachment to worldly pleasures.
Indeed, the stomach is the source of most desires and illnesses. Building on a severe craving for food, a person then longs to satisfy sexual urges and other excessive desires for wealth and fame. Then, fulfilling these frivolous wants, as well as the ills it brings about, induces another consequence of overeating, which is ingratitude.
However, experiencing hunger during the day will help a believer to yield and submit to Allah and become closer to God.
The unbeliever, a person who does not believe in the Hereafter, usually has no compelling philosophical reason to restrict his or her food intake and therefore they tend to eat seven times as much food as their body needs. Even many Muslims overeat in this manner. The way to break such a habit of overeating is by gradually eating less and less until the body becomes accustomed to eating a moderate amount of food.
One must also reflect upon the consequences in the next life. People who regularly and extravagantly overeat will be punished with hunger in the Hereafter, as repeated unnecessary satiation leads to all kinds of sins.
As such, it was not the habit of the Prophet (ṣ) to completely fill his stomach with food or drink during a meal. Sometimes he would abstain willingly as an act of ritual fasting or intermittent fasting, and at other times he went hungry because he preferred the needs of others to his own. The human stomach simply does not need to be filled and should not be filled during every meal.