tech entrepreneur bryanjohnson is spending millions trying to turn back time on his body. extreme and sometimes controversial regime of fitness, fasting, a load of tablets, tracking and treatments, and i'm back to see how it's going. it's three steps, no rail. 0k. and i have to do this now. he laughs oh, yeah. nice work. it really hits the... a little bit imbalanced, but generally... yay, i did it! yeah, good job. well done. how old am i?! a lot younger than a lot of people who pass through the house. we're back in the clinic. yeah, we're back. so if you step over here... ..on top of this. 0k. and then hold it here. right. and then i'll turn it on. but first, let me give you eye protection. lovely. thank you very much. what is this actually going to do to me? it's going to make you feel — it's going to give you energy. you love energy. is this going to feel like lying in the sun? it's going to feel like the womb. i can't remember what that felt like! they laugh are you ready? wow, it's bright — even with these on my eyes. i do it for accelerated healing, blood flow, even f