Jus Reign explains:

Waltaar, an avid lover of Mithai (Indian Sweets) finds out that he has been diagnosed with Type 2 Diabetes, which constrains him from consuming any more Mithai due to the high sugar content. So as a solution, Waltaar, alongside his former student Jassi, begin cooking fat free, low sugar, healthy Mithai and begin selling it on the streets... which leads to all sorts of drama. BREAKING BARFI. DUN DUN.

[HT: Carl Hamm]