How did Bucky live this long without visible aging?

We know how Captain America and Black Widow, both of whom are older than they look, stayed youthful looking - both have used a kind of Soldier Serum which causes rapid healing from injuries and slows down ageing.

But how did Robert 'Bucky' Barnes, who was a childhood friend of Steve Rogers (Captain America) and appears in CA2 "The Winter Soldier" manage to delay his visible aging?

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Best Answer

From scifi.se's answer on similar question

Because Bucky was also frozen for most of that time:

Dialogue from The Winter Soldier makes it clear that Hydra put Bucky back into suspended animation after completing each mission, and only unfroze him when they needed him:

Zola: The procedure has already started. You are to be the new fist of HYDRA. Put him on ice.

[...]

Hydra Scientist: He's been out of cryo freeze too long.

^{Captain America: The Winter Soldier (2014)}

Rest we have also seen from Captain America: The Winter Soldier and Captain America: Civil War that he has similar physical abilities like Captain America. So he also didn't aged like Captain America due to getting frozen. We also see few more humans treated with same Winter Soldier program in Civil War, which also didn't age a bit due to being in cryogenic sleep.

How Captain survived freezing has also been asked and answered below:

How did Captain America survive being frozen for 70 years in ice?