Lukaku joined Inter Milan for £75 million last month, securing a long-mooted move after a difficult summer.
Now playing under Antonio Conte, the Belgian says he is feeling more appreciated.
Lukaku faced criticism from fans and ex-players alike at Old Trafford, and the striker feels as though he was blamed for Jose Mourinho's failure during the 2018/19 season.
Lukaku was specifically criticised for his weight by ex-United defender and Sky Sports pundit Gary Neville.
"Normally I have a fine digestive system," Lukaku said.
"I digest everything very quickly. That's how it had been my entire life.
"But what the nutritionist (at Inter) said to me was that it had stopped working. I'm good now. My body is in the zone."
Lukaku has hit the ground running in Italy, having scored on his debut for Inter, and cites Conte as a main reason for his revival.
"The guy can make a team," Lukaku explained.
"It's already like the guys have been there for many, many years together, even the ones who just arrived. It's the strangest thing."
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