Why would one's calves hurt after quitting processed sugar?

Probably an abrupt change in lactate production. Glucose affects lactate production, and lactate production causes muscle pain. "Feel the burn! Feel the burn" That "burn" is lactate telling your body to produce more muscle tissue.

Boomerang effect when doing a detox.

The body is saying WTF?

It will pass soon!

PS: Try extra multi minerals especially magnesium, really helps,

also Epsom salt soaks and or magnesium oil rubbed in

and steamed green veggies.

Withdrawal symptoms. It should pass. But if it doesn't ask a Dr or a dietician.
Good luck !

Mine didn’t. Are you sure there’s a connection ?