Rushed to Hospital
After Heart Scare
The pic shows Kevin wearing an oxygen mask earlier today in Australia, where he was shooting a reality show, "Excess Baggage."
Federline -- who is 33 years old and significantly overweight -- was playing football with an Australian rules football team when he fell ill. K-Fed, who is 6', weighs 231 lbs.
We're told he spent the night in the hospital for observation.