Why is fasting allowed in Buddhism?

One of the answers to this question 'https://buddhism.stackexchange.com/questions/2303/is-there-a-tradition-or-practice-involving-fasting-in-buddhism-or-buddhist-count ' says that fasting is followed by Tibetan Buddhists. Why is fasting allowed since it is as extreme as gluttony and not a middle way? If I am right, following the path of the śramaṇic and yogic systems which existed at the time of Gautama Buddha, he subjected his body to extremes such as fasting and then realized that such extremes do not help in his enlightenment. Has the Buddha prohibited fasting in any of his teachings?