Fasting not only atones for past sins, but helps us to avoid future sins.

Modern science may lead us to modify this language to some degree, but it does seem that meat does contribute to libido

– thus, St. Thomas may not be so far off after all.

As stated above (Article 6), fasting was instituted by the Church in order to bridle the concupiscences of the flesh, which regard pleasures of touch in connection with food and sex.Wherefore the Church forbade those who fast to partake of those foods which both afford most pleasure to the palate, and besides are a very great incentive to lust. Such are the flesh of animals that take their rest on the earth, and of those that breathe the air and their products, such as milk from those that walk on the earth, and eggs from birds. For, since such like animals are more like man in body, they afford greater pleasure as food, and greater nourishment to the human body, so that from their consumption there results a greater surplus available for seminal matter, which when abundant becomes a great incentive to lust.Hence the Church has bidden those who fast to abstain especially from these foods.