user7141: Is it essential or somehow profitable to be vegetarian when doing "Metta/Maithree" meditation?
Or Is it essential or somehow profitable to any other form of meditation?
If not why a lot of people seems to be becoming vegetarian some time after they start their path?

user295: One part of your bodily sensations are due to food we take. Light vegetarian food can help concentration and meditation including Metta. This is beneficial but not necessary.
Buddhism is not an extreme ideology and centres around intention. If you do not have the intention of killing and also the situation is not such what you would be tainted by the guilt that an animal was killed on by behalf, then there is nothing wrong to eat non Veg. food. The main thing is keeping your mind pure and conducive to meditate hence if you find yourself uneasy or guilty about eating non Veg. food then it will be beneficial to give up.
But if you are a monk you have no choice but accept what has been offered.

user-1: Based on Theravada, which is what I'm most familiar with, vegetarianism is not essential for any meditation that I know of. Even so, I've chosen to be a vegetarian. As I understand it, the Mahayana tradition tends to strongly encourage vegetarianism, but even then I'm not certain if they do it specifically to aid meditation practice.
As to it being profitable, it depends on what effects adopting vegetarianism has on that person's state of mind. If being a vegetarian helps your compassion towards beings, then you might consider it profitable. For some people, choosing vegetarianism might result in no improved state of mind, in which case it doesn't matter. 
This also answers your third question as to why a lot of people become vegetarian after they start their path. They might have noticed that becoming a vegetarian, for them, improves their personal state of mind. Of course this won't be the only reason, but for some it might be. 
Try it, and see what works for you. 

user254: When my SO became vegetarian she said she liked animals (e.g. horses and cows and so on) and other living creatures; and said it would be hypocritical to cause them (e.g. to pay a butcher for them) to be killed for her to eat.
I think she felt that being non-vegetarian (i.e. that being a carnivore or predator) would interfere with or cloud her perception of her love for living animals.

I think there's some justification for that in a text like the Dhammapada, for example in the whole chapter on violence, which starts for example with,

All tremble at violence; all fear death. Putting oneself in the place of another, one should not kill nor cause another to kill.


I think that, logically, that justification depends on three assumptions:

That the "all" (who tremble at violence) includes annimals, i.e. sentient beings
That lay people who buy their food encourage or cause killing if they pay for meat (that argument is slightly different or doesn't apply to monks who take alms and who eat whatever they are given)
That vegetarianism is feasible (practicable) and is not contrary to the doctrine of the middle way


user-1: Vegetarianism is sila or part of the training in virtue.  According to Buddhaghosa, such moral discipline serves two functions - to compose the mind and to aid in the cultivation of non-regret.  I'd say it's fairly obvious that if you are on the cushion and worrying about what you take to be a contradiction between your actions and the lovingkindness meditation you are practicing, then yes, you might benefit from vegetarianism.
It's important to understand, however, that eating meat isn't going to "short circuit" your metta meditation.  If that were the case, than the whole of Tibetan Buddhism would be marked by deficiencies in lovingkindness!  I will say, however, that eating a vegetarian diet does amazing things for your concentration and that these benefits extend well beyond the absence of regret.  Like anything else, the proof of the pudding is in the eating, right?  Just not a meat pudding in this case.  ;-)              

7141: <p>Is it essential or somehow profitable to be vegetarian when doing "Metta/Maithree" meditation?</p>

<p>Or Is it essential or somehow profitable to any other form of meditation?</p>

<p>If not why a lot of people seems to be becoming vegetarian some time after they start their path?</p>
 295: <p>One part of your bodily sensations are due to food we take. Light vegetarian food can help concentration and meditation including Metta. This is beneficial but not necessary.</p>

<p>Buddhism is not an extreme ideology and centres around intention. If you do not have the intention of killing and also the situation is not such what you would be tainted by the guilt that an animal was killed on by behalf, then there is nothing wrong to eat non Veg. food. The main thing is keeping your mind pure and conducive to meditate hence if you find yourself uneasy or guilty about eating non Veg. food then it will be beneficial to give up.</p>

<p>But if you are a monk you have no choice but accept what has been offered.</p>
 -1: <p>Based on Theravada, which is what I'm most familiar with, vegetarianism is not essential for any meditation that I know of. Even so, I've chosen to be a vegetarian. As I understand it, the Mahayana tradition tends to strongly encourage vegetarianism, but even then I'm not certain if they do it specifically to aid meditation practice.</p>

<p>As to it being profitable, it depends on what effects adopting vegetarianism has on that person's state of mind. If being a vegetarian helps your compassion towards beings, then you might consider it profitable. For some people, choosing vegetarianism might result in no improved state of mind, in which case it doesn't matter. </p>

<p>This also answers your third question as to why a lot of people become vegetarian after they start their path. They might have noticed that becoming a vegetarian, for them, improves their personal state of mind. Of course this won't be the only reason, but for some it might be. </p>

<p>Try it, and see what works for you. </p>
 254: <p>When my <a href="https://en.wikipedia.org/wiki/Significant_other" rel="nofollow">SO</a> became vegetarian she said she liked animals (e.g. horses and cows and so on) and other living creatures; and said it would be hypocritical to cause them (e.g. to pay a butcher for them) to be killed for her to eat.</p>

<p>I think she felt that being non-vegetarian (i.e. that being a carnivore or predator) would interfere with or cloud her perception of her love for living animals.</p>

<hr>

<p>I think there's some justification for that in a text like the Dhammapada, for example in <a href="http://www.accesstoinsight.org/tipitaka/kn/dhp/dhp.10.budd.html" rel="nofollow">the whole chapter on violence</a>, which starts for example with,</p>

<blockquote>
  <p>All tremble at violence; all fear death. Putting oneself in the place of another, one should not kill nor cause another to kill.</p>
</blockquote>

<hr>

<p>I think that, logically, that justification depends on three assumptions:</p>

<ul>
<li>That the "all" (who tremble at violence) includes annimals, i.e. <a href="https://en.wikipedia.org/wiki/Sentient_beings_(Buddhism)" rel="nofollow">sentient beings</a></li>
<li>That lay people who buy their food encourage or cause killing if they pay for meat (that argument is slightly different or doesn't apply to monks who take alms and who eat whatever they are given)</li>
<li>That vegetarianism is feasible (practicable) and is not contrary to the doctrine of the middle way</li>
</ul>
 -1: <p>Vegetarianism is sila or part of the training in virtue.  According to Buddhaghosa, such moral discipline serves two functions - to compose the mind and to aid in the cultivation of non-regret.  I'd say it's fairly obvious that if you are on the cushion and worrying about what you take to be a contradiction between your actions and the lovingkindness meditation you are practicing, then yes, you might benefit from vegetarianism.</p>

<p>It's important to understand, however, that eating meat isn't going to "short circuit" your metta meditation.  If that were the case, than the whole of Tibetan Buddhism would be marked by deficiencies in lovingkindness!  I will say, however, that eating a vegetarian diet does amazing things for your concentration and that these benefits extend well beyond the absence of regret.  Like anything else, the proof of the pudding is in the eating, right?  Just not a meat pudding in this case.  ;-)              </p>
