If you could live forever, would you? Bryan Johnson, 47, is determined to try. He wakes up at 5 a.m., follows a strict vegan diet, and tracks over 100 health metrics every day. He’s undergone gene therapy, received plasma transfusions from his teenage son, and had 300 million stem cells injected into his joints. Johnson says it's working — and that his body ages just 7.6 months for every year.