Effect of meat on the body
Lets get a little technical here. Flesh eating animals have sharp teeth for tearing flesh and no molars unlike humans, who are exactly the opposite. All carnivores have acidic saliva where as human beings have alkaline saliva; which is not suitable for predigesting flesh. Moreover, the hydrochloric acid in human saliva is 20 times weaker than those in carnivores.
The most wonderful argument is yet to follow. Carnivores have an intestine about 3 times their body length. This is because meat decays rapidly and has to be disposed of as soon as possible. Animals have all necessary resources and body structure for digesting meat as discussed before, and a shorter intestine is sufficient to absorb the nutrients. However, in humans, the intestine is about 12-14 times the body length, and conditions for digesting meat - poor. Hence the meat decays half way through the intestine, and if you are the unlucky one, it also sticks to the walls of your intestines.
For a normal human being, the meat takes 4 days to pass all the way through the intestine and move out. But this duration has been shown to vary up to 3 months, however in some cases decayed meat has been found to be inside the intestine for over 22 years! This decayed meat provides comfortable hosting to a wide range of bacteria, which often prove to be fatal parasites. So, how do you like the idea of being a germ holiday resort?
The carnivore it, you will argue that meat, has protein and proteins are building blocks of life. Meat contains proteins, true. But excessive protein is shown to overload the kidneys and result irreversible changes in its functioning. It has also been linked to colon cancer.
Violence against animals
Rising above the technical stuff, at least think of the violence involved. Animals are often kept in inhuman conditions and are given a painful death. A survey reported that animals are reared for consumption like goats, cows, buffalos, hens etc, gobble down a whopping 50% of the food grains meant for human beings. These animals are reared exclusively to become McDonald's quarter pounders and KFC's variety of chicken dishes.
Thus, apart from eating the animal itself you're also eating more than your share of food grain (indirectly of course) and somebody else has to forego his/her meal to feed you and the animal that you just stuffed down your throat. Is there no end to such gluttony in the world?
How eating fruits/vegetables is different from eating animals
Some people will be wondering that even killing plants involves violence, I'm just getting there. Firstly, a plant does not die if we take some leaves, vegetables or fruits or any other plant materiel, because these thing will grow again naturally. Secondly, it is agreed that both plants and animals have life, but the animals have a well-developed nervous system which the plants lack. Because of this nervous system, animals, like human beings, feel pain when they're hurt. On the other hand the plants don't feel pain when they're cut and many times subsisting on them may not involve killing - for example eating fruits and vegetables.
If it is agreed that one living being serves as food of another living being, then in this aspect, these animal killer are not doing anything wrong because one living being is food for another living being. This means we can just eat any animal available-dogs, cats, sheep, etc.
One has no right to take life if we cannot give life. Like Paul McCartney (former Beatles singer) said "If slaughterhouses had glass walls, everyone would be vegetarian" (because no one knows where it comes from....) and for those of you who would still want to continue eating meat and imitate carnivores do it perfectly! Don't just imitate a part of it. I've never seen a lion go to a restaurant to get his meat cooked/ smoked/roasted or whatever before eating. Try eating it raw!
People of many parts of the present world become Pure vegetarian for many reasons. Many of my friends told me that the elephant is having good physique and strength being it is a vegetarian and there is no meaning of eating non-vegetarian only brings a good physique and strength.