In India, Depending on the castes, It is said that a brahmin should not eat any kind of non vegetarian food and people of other castes should eat Non Vegetarian food like chicken , mutton, sea food. According to Indian Customs, if we observe, Basically, who should eat and who should not depends on the occupation of a person but not on their caste. Depending on the work they were categorised earlier and later we people misunderstood the concept and treated it vice versa. If you ask any doctor regarding this, he will simply tell you that if you have need for more calories and you do a lot of physical labor, then only you should eat non vegetarian food. If your occupation is of sedentary type and you eat a lot of high-calorie food, you are bound to gain more weight and invite many sorts of diseases related to obesity.
The medieval caste system of India was based upon the occupation of a person. Therefore the people from a particular caste doing more physical labor were allowed to eat meat. For example, job of a Kshatriya was to fight with enemy and protect the people. So, they required a lot of energy. Hence, Kshatriyas were allowed to eat meat, Non vegetarian food. In the same way, a farmer who requires a lot of physical work was allowed to eat Non veg food. On the other hand, Other castes like Brahmins who do Prayers and intelligent work requiring less hard labor were restricted from eating non vegetarian food according to indian traditions. In the same way, weavers, businessmen were not allowed to eat any kind of non vegetarian.
Aside from that, some non vegetarian products like meat and chicken are hard to digest. If you do not have enough body movement or what we say Exercise, it will be hard for you to digest that food and you will be unnecessarily inviting the ailments.
Vaishnavas by most means are pure Vegetarians (irrespective of caste, Yes there are non Brahmin Vaishnavas too)
Shaivas and Shaktas fall in between. Those who follow Agama Shastras and Advaita philosophy and such Vedanta schools of thoughts are mostly vegetarian. Similarly those who adhere to Devi Bhagawatham and Smartha thought in Shaktas are mostly vegetarians.
Those who follow Tantric Shaivism/Shaktism or few Shaiva Siddanta thoughts or local cults or those who live near to the sea are generally non-vegetarians.
The practice of guna based diet is so much stressed only in Bhagavat Geeta, so mostly Vaishnavas do not consume meat. For the same reason organizations like ISKCON are very particular in practicing Vegetarianism.