Joshua regained his three world titles with a unanimous points win over the Mexican, who looked sluggish compared the fighter who knocked the Bit out in the seventh round last time around.
Video clips on twitter had showed Ruiz Jr tucking into a big platter of Mexican food at an unspecified point between the two fights.
The California-based power-puncher came in weighing 20st 3lbs and said that he only had himself to blame for his lack of stamina and energy.
He told Sky Sports: “I didn’t prepare how I should’ve and gained too much weight. He won and outboxed me but best believe if we do a third fight I’m going to get in the best shape of my life.
“I thought I was going to feel stronger and better but next fight I admit I’m going to be more prepared. I was chasing him instead of cutting the rings. I felt like I couldn’t throw my combinations.”
Ruiz Jr called for a third battle after his defeat, to round off the trilogy which currently stands at 1-1.
But he was humble in defeat, as Joshua was when he tasted defeat for the first time in his career in New York.
“I’m sorry Manny,” he said to his trainer Manny Robles.
“I’m sorry to my Dad too. They told me I was too heavy. I think the partying got the better of me.”
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