Some Buddhists today are vegetarians.
But Siddharta, in his time, ate and drank what was given to him, as was his way.
To understand this we need to look at the nature of early Buddhism and the dietary habits of the population at large then that we can understand why the Buddha allowed meat-eating.
Buddhist monks and nuns were mendicants; that is, they begged for their food from householders.
They didn't have the opportunity to grow their own food.
That is to say they ate what they got from people.
There are some texts in the matter:
"I say that in three situations flesh can be partaken of - when it is not seen, heard, or suspected (that an animal has been killed for a monk)."
- the Jivaka Sutta
At that time, Arya(sage) Mahamati(Great Wisdom) Bodhisattva-Mahasattva said to the Buddha:
"Bhagavan(World Honored One), I see that in all worlds, the wandering in births and deaths, the enlaced animosities, and the falling into evil paths, are all caused by meat eating and cyclical killing.
Those behaviors increase greed and anger, and make living beings unable to escape from suffering. That is truly very painful."
Bhagavan, people who eat meat are destroying the great merciful seed of their own, thus the people who practice the holy Way should not eat meat. "
Bhagavan, the Exterior-paths practitioners preach the incorrect theories which may fall into the mundane views, nihilism, eternalism, existentialism, or non-existence-ism, however, all of their theories forbid meat eating, they do not eat meat and do not allow others to eat meat.
So would it be possible that, for the cultivators who practice Brahma-behavior(Brahma-carya) according to the pure Dharma of Tathagata(Thus Come One), there is no rule to forbid meat eating?
The Tathagata, the Bhagavan equally gives his mercy and compassion to all living beings, how could he allow meat eating?
Virtuous Bhagavan, please tell us the offences of meat eating, and the meritorious virtues of not eating meat.
Once we have heard it, all the Bodhisattvas and I will faithfully practice it, widely preach and spread it abroad, to make all living beings of the past, the present, and the future be aware of it."
The Buddha told Arya Mahamati Bodhisattva: "Good, good, Mahamati, you are greatly compassionate, having pity on all living beings, you asked this question. Now listen attentively and I'll tell you."
Mahamati Bodhisattva said to the Buddha: "How virtuous, Bhagavan! Yes I'll accept the teaching."
The Buddha told Mahamati: "Meat eating has countless offences.
All Bodhisattvas should cultivate their great mercy and compassion so that they should not eat meat.
Now I am telling you in brief the merits of not eating meat, and the offences of meat eating, please listen attentively.
Mahamati, I see that from the beginningless time, because of the habit of meat eating and the greed for flavors of meats, living beings kill and hurt each others in never ending cycles, thus they are apart from sages and suffering from births and deaths."
Those who renounce the flavor of meat can taste the flavors of the true Dharmas, truthfully practice the Bhumi(stage)s of Bodhisattva, and attain Anuttara-Samyak-Sambodhi quickly.
They can then make all living beings enter the resting-place of Sravaka(voice-hearer) and pratyeka-buddha(self-enlightened one), and after that make them enter the stage of Tathagata."
Mahamati, these benefits are based on the merciful heart.
People who eat meat are destroying the great merciful seed of their own, then how could they get these great benefits?
Mahamati, I see that living beings are in the transmigration of the six paths, being together in births and deaths, they give birth to and foster each others, and cyclically become fathers, mothers, brothers and sisters of each others; They may be men or women, may be the direct line of descent, may be cousins, affinities, uncles, aunts, sons, daughters, grandsons, and other various relatives of each others; They may also be born in other paths(of animal, ghost, god, and so on.), whether virtuous or evil, they frequently become the relatives of each others.
Because of these relationships, I see that all meats eaten by living beings are of their own relatives.
Due to the greed for flavors of meats, the living beings circularly eat each others, then they always have the thoughts of hurting each others.
Their painful karmas are always increasing, so they are wandering in cycles of births and deaths and unable to escape.""
- Lankavatara sutta
My advice in the matter?
A term that matches "the middle path" with is "moderation".
Take everything in moderation is what Siddharta came to realize.
In the case of the Lankavatara sutta, the "evil act" lies not in the eating, but in the causes behind the eating, (view the last lines, the underlined...) and so are in violation of the spririt of the precepts.
You can eat but don't eat in excess.
You can watch what you eat but don't starve yourself
Just be mindful of it.
May the force be with you