LEV749 Do not eat and drink as a low-life. Generally speaking, most of a person's sins stem from overindulgence in food and drink. [Such is written explicitly (Devarim 32:15),וַיִּשְׁמַ֤ן יְשֻׁרוּן֙ וַיִּבְעָ֔ט שָׁמַ֖נְתָּ עָבִ֣יתָ כָּשִׂ֑יתָ וַיִּטֹּשׁ֙ אֱלֹ֣והַ עָשָׂ֔הוּ--But Yeshurun waxed fat and kicked; you became fat, thick--and forsook God Who made him.” Similarly, our Sages teach (Berachos 32a), מלי כרסיה זינא בישא--Having filled his stomach, a man will come to do wretched deeds”]. The reason is that food is עיסת החומר—“yeast (an ingredient that causes ‘rising’) of the physical.” By contrast, reflection upon wisdom, fear of Heaven and Hashem's precious commandments is “yeast” of the soul. Man's body and soul are diametrical opposites, so that at a time when one's body is “rising” because of its “yeast,” one’s soul is weakened to a certain extent. For this reason, there were Sages who did not partake of food more than what was necessary to sustain their souls. For our benefit and with this idea in mind, the Torah forbids us to overindulge in food and drink, for such excesses cause an “uprising” of the body to the point where the soul is virtually crushed and destroyed. Why is the Torah’s warning about this excess addressed specifically to an adolescent [the laws of the “rebellious son” apply only during the first three months after a boy’s bar mitzvah]? Is because just then his desires peak and he becomes obligated to take precautions for the sake of this soul. From a law that applies to but three months of adolescence, he must learn an ethical lesson that is critically important for as long as he lives.