The Rambam Diet
דכתיב והעומר עשירית האיפה הוא מכאן אמרו שבעה רבעים קמח ועוד חייבת בחלה שהן ששה של ירושלמית שהן חמשה של ציפורי
The Gemara responds: The Torah states that the manna, the dough of the wilderness, was “an omer a head” (Exodus 16:16). A later verse elaborates on that measure, as it is written: “And an omer is the tenth part of an eifa” (Exodus 16:36). An eifa is three se’a, which are eighteen kav or seventy-two log. An omer is one-tenth of this measure. From here, this calculation, Sages said that dough prepared from seven quarters of a kav of flour and more is obligated in ḥalla. This is equal to six quarter-kav of the Jerusalem measure, which is five quarter-kav of the Tzippori measure. (A Kav is approximately 1.46 quarts NOT to be relied on halakhically.)
מכאן אמרו האוכל כמדה זו הרי זה בריא ומבורך יתר על כן רעבתן פחות מכאן מקולקל במעיו:
From here the Sages also said: One who eats roughly this amount each day, is healthy, as he is able to eat a proper meal; and he is also blessed, as he is not a glutton who requires more. One who eats more than this is a glutton, while one who eats less than this has damaged bowels and must see to his health.
Let’s look at the standards for healthy eating from the Rambam Deos 4:1-2:
הוֹאִיל וֶהֱיוֹת הַגּוּף בָּרִיא וְשָׁלֵם מִדַּרְכֵי הַשֵּׁם הוּא. שֶׁהֲרֵי אִי אֶפְשָׁר שֶׁיָּבִין אוֹ יֵדַע דָּבָר מִידִיעַת הַבּוֹרֵא וְהוּא חוֹלֶה. לְפִיכָךְ צָרִיךְ לְהַרְחִיק אָדָם עַצְמוֹ מִדְּבָרִים הַמְאַבְּדִין אֶת הַגּוּף. וּלְהַנְהִיג עַצְמוֹ בִּדְבָרִים הַמַּבְרִין וְהַמַּחֲלִימִים. וְאֵלּוּ הֵן: לְעוֹלָם לֹא יֹאכַל אָדָם אֶלָּא כְּשֶׁהוּא רָעֵב. וְלֹא יִשְׁתֶּה אֶלָּא כְּשֶׁהוּא צָמֵא. וְאַל יַשְׁהֵא נְקָבָיו אֲפִלּוּ רֶגַע אֶחָד. אֶלָּא כָּל זְמַן שֶׁצָּרִיךְ לְהַשְׁתִּין אוֹ לְהָסֵךְ אֶת רַגְלָיו יַעֲמֹד מִיָּד:
Seeing that the maintenance of the body in a healthy and sound condition is a God-chosen way, for, lo, it is impossible that one should understand or know aught of the divine knowledge concerning the Creator when he is sick, it is necessary for man to distance himself from things which destroy the body, and accustom himself in things which are healthful and life-imparting. These are: never shall man partake food save when hungry, nor drink save when thirsty; he shall not defer elimination even one minute, but the moment he feels the need to evacuate urine or feces he must rise immediately.
לֹא יֹאכַל אָדָם עַד שֶׁתִּתְמַלֵּא כְּרֵסוֹ אֶלָּא יִפְחֹת כְּמוֹ רְבִיעַ מִשָּׂבְעָתוֹ. וְלֹא יִשְׁתֶּה מַיִם בְּתוֹךְ הַמָּזוֹן אֶלָּא מְעַט וּמָזוּג בְּיַיִן. וּכְשֶׁיַּתְחִיל הַמָּזוֹן לְהִתְעַכֵּל בְּמֵעָיו שׁוֹתֶה מַה שֶּׁהוּא צָרִיךְ לִשְׁתּוֹת. וְלֹא יַרְבֶּה לִשְׁתּוֹת מַיִם וַאֲפִלּוּ כְּשֶׁיִּתְעַכֵּל הַמָּזוֹן. וְלֹא יֹאכַל עַד שֶׁיִּבְדֹּק עַצְמוֹ יָפֶה יָפֶה שֶׁמָּא יִהְיֶה צָרִיךְ לִנְקָבָיו. לֹא יֹאכַל אָדָם עַד שֶׁיֵּלֵךְ קדֶם אֲכִילָה עַד שֶׁיַּתְחִיל גּוּפוֹ לָחֹם. אוֹ יַעֲשֶׂה מְלַאכְתּוֹ אוֹ יִתְיַגֵּעַ בְּיֶגַע אַחֵר. כְּלָלוֹ שֶׁל דָּבָר יְעַנֶּה גּוּפוֹ וְיִיגַע כָּל יוֹם בַּבֹּקֶר עַד שֶׁיַּתְחִיל גּוּפוֹ לָחֹם וְיִשְׁקֹט מְעַט עַד שֶׁתִּתְיַשֵּׁב נַפְשׁוֹ וְאוֹכֵל. וְאִם רָחַץ בְּחַמִּין אַחַר שֶׁיָּגַע הֲרֵי זֶה טוֹב וְאַחַר כָּךְ שׁוֹהֶה מְעַט וְאוֹכֵל:
Man shall not eat his stomach-full, but should reduce about one fourth of the quantity which would sate him; nor shall he drink water during the meal, save a little mixed with wine; but when the food will commence to be digested in his bowels, he may drink whatever quantity he needs, nevertheless, he should not drink over-much water even after the food was digested. He shall not eat before a thorough examination of self whether there is a need for elimination. Man shall not eat without warming his body either by walking before mealtime, by some manual labor, or by some other form of exercise which will tire him. As a general rule, he shall exercise his body and tire it every day during the morning so that it will commence to perspire, when he shall rest a little until his spirit will be calm then eat. If he take a warm bath after hard exercise it is still better, after which he should rest a little then eat.
Indeed, there is scientific evidence to support that a calorie restricted diet promotes longevity. ( https://www.health.harvard.edu/healthy-eating/eat-less-to-live-longer ).
It is interesting to note that Rabbenu Yonah in Yesod HaTeshuva advises the same idea for different reasons :
וְאִם אָדָם חַלָּשׁ הוּא שֶׁאֵינוֹ יָכוֹל לִסְבּוֹל עִנּוּיִים קָשִׁים וְתַעֲנִיּוֹת, יִמְשׁוֹךְ מִתַּאֲווֹתָיו. וְאַל יְמַלֵּא כָּל תַּאֲווֹתָיו, לֹא בְמַאֲכָל וְלֹא בְמִשְׁתֶּה. וְכֵן אָמַר הָרַב רַבִּי אַבְרָהָם בַּר דָּוִד שֶׁהָיָה אֶחָד מֵחֲסִידֵי עוֹלָם, הַגָּדֵר הַגָּדוֹל הַמְעֻלֶּה הַמֻּפְלָא, מְנִיעַת הַמַּאֲכָלוֹת. וְכֵן פֵּרַשׁ דְּבָרָיו, אַל יַעֲזֹב לְגַמְרֵי מִלֶּאֱכוֹל בָּשָֹר וְלִשְׁתּוֹת יַיִן, כִּי דַיֶּיךָ מַה שֶּׁאָסְרָה תוֹרָה. אַךְ בְּעֵת מַאֲכָלוֹ וְעוֹדֶנּוּ תָאֵב לֶאֱכוֹל, יַנִּיחַ מִמֶּנּוּ לִכְבוֹד הַבּוֹרֵא מִתַּאֲווֹתָיו וְאַל יֹאכַל כְּפִי תַאֲוָתוֹ. וְדֶרֶךְ זוֹ תִמְנָעֶנּוּ מֵחֲטוֹא וְתַזְכִּירֶנּוּ אַהֲבַת הַבּוֹרֵא יוֹתֵר מִתַּעֲנִית אֶחָד בַּשָּׁבוּעַ, כִּי זֶה בְּכָל יוֹם תָּמִיד, מִדֵּי אָכְלוֹ וּמִדֵּי שְׁתוֹתוֹ, יַנִּיחַ מִתַּאֲוָתוֹ לִכְבוֹד הַבּוֹרֵא:
So whether you will contemplate stopping before you are full out of health reasons, or out of musar-teshuva reasons, it is plainly evident the benefits that this can offer such as mindfulness, respect for one's body, health, and humility.
for Video Shiur click here to listen: Psychology of the DAF Eruvin 83
Translation Courtesy of Sefaria
Translations Courtesy of Sefaria, except when, sometimes, I disagree with the translation 
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