At 173 cm (5 ft 8 in) and 64 kg (141 lb), Lee was renowned for his physical fitness and vigor, achieved by using a dedicated fitness regimen to become as strong as possible. After his match with Wong Jack Man in 1965, Lee changed his approach toward martial arts training. Lee felt that many martial artists of his time did not spend enough time on physical conditioning. Lee included all elements of total fitness—muscular strength, muscular endurance, cardiovascular endurance, and flexibility. He used traditional bodybuilding techniques to build some muscle mass, not overdone as that could decrease speed or flexibility. At the same time in balance, Lee maintained that mental and spiritual preparation are fundamental to the success of physical training in martial arts skills. In Tao of Jeet Kune Do he wrote,
Training is one of the most neglected phases of athletics. Too much time is given to the development of skill and too little to the development of the individual for participation. ... JKD, ultimately is not a matter of petty techniques but of highly developed spirituality and physique.
According to Linda Lee Cadwell, soon after he moved to the United States, Lee started to take nutrition seriously and developed an interest in health foods, high-protein drinks and vitamin and mineral supplements. He later concluded that in order to achieve a high-performance body, one could not fuel it with a diet of junk food, and with "the wrong fuel" one's body would perform sluggishly or sloppily. Lee also avoided baked goods and refined flour, describing them as providing calories which did nothing for his body.
On May 10, 1973, Lee collapsed during an ADR session for Enter the Dragon at Golden Harvest in Hong Kong. Suffering from seizures and headaches, he was immediately rushed to Hong Kong Baptist Hospital where doctors diagnosed cerebral edema. They were able to reduce the swelling through the administration of mannitol. The headache and cerebral edema that occurred in his first collapse were later repeated on the day of his death.
On July 20, 1973, Lee was in Hong Kong, to have dinner with James Bond star George Lazenby, with whom he intended to make a film. According to Lee's wife Linda, Lee met producer Raymond Chow at 2 p.m. at home to discuss the making of the film Game of Death. They worked until 4 p.m. and then drove together to the home of Lee's colleague Betty Ting Pei, a Taiwanese actress. The three went over the script at Ting's home, and then Chow left to attend a dinner meeting.
Later Lee complained of a headache, and Ting gave him an analgesic (painkiller), Equagesic, which contained both aspirin and the tranquilizer meprobamate. Around 7:30 p.m., he went to lie down for a nap. When Lee did not turn up for dinner, producer Raymond Chow came to the apartment, but was unable to wake Lee up. A doctor was summoned, who spent ten minutes attempting to revive Lee before sending him by ambulance to Queen Elizabeth Hospital. By the time the ambulance reached the hospital he was dead. He was 32 years old.
There was no visible external injury; however, according to autopsy reports, Lee's brain had swollen considerably, from 1,400 to 1,575 grams (a 13% increase). The autopsy found Equagesic in his system. On October 15, 2005, Chow stated in an interview that Lee died from an allergic reaction to the tranquilizer meprobamate, the main ingredient in Equagesic, which Chow described as an ingredient commonly used in painkillers. When the doctors announced Lee's death officially, it was ruled a "death by misadventure".
Lee's wife Linda returned to her hometown of Seattle, and had him buried at lot 276 of Lakeview Cemetery. Pallbearers at his funeral on July 25, 1973 included Taky Kimura, Steve McQueen, James Coburn, Chuck Norris, George Lazenby, Dan Inosanto, Peter Chin, and Lee's brother Robert.