Jamieson, Fausset and Brown on 2 Corinthians 11:27

27. fastings--voluntary, in order to kindle devotions (Ac 13:2, 3; 14:23; 1Co 9:27); for they are distinguished from "hunger and thirst," which were involuntary [Grotius]. However, see on 2Co 6:5. The context refers solely to hardships, not to self-imposed devotional mortification. "Hunger and thirst" are not synonymous with "foodlessness" (as the Greek of "fasting" means), but are its consequences.

cold ... nakedness--"cold" resulting from "nakedness," or insufficient clothing, as the Greek often means: as "hunger and thirst" result from "foodlessness." (Compare Ac 28:2; Ro 8:35). "When we remember that he who endured all this was a man constantly suffering from infirm health (2Co 4:7-12; 12:7-10; Ga 4:13, 14), such heroic self-devotion seems almost superhuman" [Conybeare and Howson].