Marko Arnautovic says he underestimated the Chinese Super League after joining last year from West Ham United, admitting "I didn't look after my body" and gorged on fizzy drinks.
The Austrian forward signed for Shanghai SIPG for a reported 25 million euros and despite scoring nine goals in 15 games, came in for criticism in some quarters.
"I underestimated it, I was not fit enough, I didn't prepare myself as I should," the 31-year-old said.
"I didn't train, I didn't look after my body, I was eating, I was drinking fizzy drinks -- Sprite, Coca-Cola, Fanta -- all these sugar drinks that are not good for the body.
"Eating at wrong times. Not sleeping because when I came to China it took me about three weeks until I could adapt to the time.
"I went to bed at 6, 7 o'clock in the morning. I woke up 3, 4 o'clock in the afternoon, went to training, stayed up again all night, eating at wrong times."
Arnautovic, who joined SIPG in July last year, has made a fast start to the coronavirus-delayed new season.
Playing alongside former Chelsea star Oscar and the Brazilian forward Hulk, Arnautovic has scored five goals in eight CSL matches to help SIPG make an unbeaten start to the campaign.
He also laid on an assist for Oscar with a clever backheel in a recent 2-1 win over title rivals Beijing Guoan.
"I don't need to hear from any media, or I don't need to hear it from any fans, the criticism," said Arnautovic, previously also of Stoke City and Inter Milan.
"I am my biggest critic so if I don't do well I will tell myself, 'You didn't do well, you need to do better.'"