Gemara:


Ein Ayah: Since eating is one of the major physical enjoyments that the masses are drawn to it makes sense to eat separately. Indeed, philosophers believed eating is an embarrassment that should not be done in a social setting. However, using one’s senses to straighten his path has an elevating benefit, which, when achieved, makes it not degrading but an honor.
Three people eating together are the minimum to be called a group or gathering and to clarify the gains of joining together. Specifically, it is possible to significantly refine one’s characteristics and broaden the way he seeks out the ways of Hashem by observing other ways of righteousness. Thereby, Hashem’s Name will be glorified in His world. When the intellect is developed and spiritual benefits are elevated, then as more people join together, things improve innately. Each person brings his successes in arriving at shleimut, true ways of looking at things, and straight ways of living.
From the perspective of food’s physical pleasures, though, the more people are present, the less food is available for every individual. One benefits from people joining together only if it has pragmatic value. Otherwise, he has no gain from his friend, and there is little reason for camaraderie. In contrast, when the intellectual foundation of knowledge of Hashem in the world will be set, people will be emotionally drawn to love all that Hashem does for us with love in the truest sense. At that point, friendship will have its most positive effect. In order to strengthen friendship that accompanies using physical experiences for spiritual growth, people should be brought together to thank Hashem. Then they can experience the full advantage of togetherness. That is why three who eat together must do Birkat Hamazon together, as well.

Proper Health Habits for a Talmid Chacham
(condensed from Ein Ayah, Berachot 7:5)

Gemara:


Ein Ayah: Rabbi Zeira chose a path of extreme humility, treating himself as one who is far from proper shleimut in service of Hashem and pure characteristics. That is why he accepted upon himself a life of asceticism, as described in Bava Metzia 85a. This is hinted at in his nickname of "burnt thighs," for the body can be compared to a leg in comparison to the godly soul. The idea behind the burnt thighs is that if one deprives his body of what it needs, the spirit will also lack the status it deserves. Rabbi Zeira needed to know that he did not need any more self-affliction, such as multiple fasts, which weakened his body. The reason they called him small is that he saw himself as lacking due to his extreme humility, as Chazal said about the biblical Yoktan (Bereishit Rabba 6:4). Although the humility is basically good, cases of excess, such as the story in which his legs were burnt, were unfortunate.
Rabbi Avahu suspected that Rabbi Zeira’s illness might have to do with his traditional self-deprivation. To stress that this is not proper for those who learn Torah (see Ta’anit 11b), he pledged specifically to make festivities for the rabbis if Rabbi Avahu recovered to show that some indulging is good, as the rabbis should avoid deprivation. It stresses that he made the meal for all of the rabbis to show that the path of healthy living is a mainstream one for them. Extreme behavior is appropriate only for extreme cases or people.