Discontinuing meat may cause temporary perceived weakness because of the removal of stimulating properties, but the body ultimately benefits from the change.

Original passage

When the use of flesh food is discontinued, there is often a sense of weakness, a lack of vigor. Many urge this as evidence that flesh food is essential; but it is because foods of this class are stimulating, because they fever the blood and excite the nerves, that they are so missed. Some will find it as difficult to leave off flesh eating as it is for the drunkard to give up his dram; but they will be the better for the change.