Nolito credited Luis Enrique for helping him realise his true potential by convincing him to give up cakes and Coke as he prepares to face his former coach when Manchester City visit Barcelona in the Champions League.
Spain forward Nolito played under the stewardship of Luis Enrique at Barcelona B, before reuniting with him at Celta Vigo in 2013.
Nolito almost returned to Camp Nou in January before ultimately moving to Manchester City but says the 46-year-old has been crucial for his career.
"Luis Enrique appeared at a moment in my career where it was either take a step forward or a step back," he said in an interview with the Guardian.
"I was at Barcelona B with him, then Celta. He bet very, very heavily on me and supported me. He made me see football differently, convincing me I could really make it.
"I [had] always played carrying extra kilos. He made me see that it was fundamental to lose weight, 10 kilos, to make the breakthrough.
"He was pesado [insistent], for my own good. It was hard, but there's been a massive change. Brutal.
"He was on at me every day; he's been fundamental for my career. The cakes, the bread, the Coke: it's all good but for my profession it was s***.
"I'd train then eat: train, eat, train, eat. I was a fish biting its own tail. Eventually, you realise an elite player has to be fino [slim]."
Nolito admits that a move to Barca, where he would have faced competition from Lionel Messi, Luis Suarez and Neymar, almost materialised, and says the decision to leave the comfort of Celta was down to a desire for trophies.
"It was close with Barcelona but in the end I chose City," he added.
"The last three years at Celta have been the best of my life but it was time to go, the right moment. I'd like to win something before my career is over and I think I can at City."