As a veteran of two complete marathons in Australia, comedian Kunihiro Matsumura must have thought he would have no problem running the Tokyo Marathon on Sunday.

But carrying 101 kg on his 165 cm frame was too much for the 41-year-old, who suffered a heart attack around the 14.7 km point on the 42.195 km course. He briefly passed out but is on the mend, his agent reported Thursday night.

Dr. Itsuki Yuzawa, a specialist in sports medicine at Terada Hospital in Adachi Ward, Tokyo, warns overweight people to slim down before joining the jogging boom.

"In general, the obese, especially those over 100 kg, are highly likely to suffer hypertension and sclerosis, which makes it easy to have a heart attack."

Another disadvantage for the obese is that they require more blood than normal in their muscles because their bodies are so big, he said.

"I don't know if Matsumura is suffering from hypertension or sclerosis, but even healthy people die suddenly from a heart attack when they play sports. Those who are overweight should be extra careful," he said.

Matsumura's manager declined to say if the comic had hypertension or sclerosis.

Yuzawa said when people feel dizzy or unwell, they should get a checkup to find out if they have any hidden heart problems.

"To minimize the risk, you have to know your heart condition, drink lots of water when running and, better yet, do not run a marathon," he said.

Matsumura dropped out of the Tokyo Marathon last year.