I know its comparing animals but tempted to think these life extending factors can apply to human lifespan.

External factors

• frigid cold environments causes lower heartbeat and metabolism, can be achieved by living in cold places and doing not too much activities. Not sure if I am willing to move and live in a colder environment. Although I do love swimming relaxed in the cold water like a whale.
• As much low activities may be low heartbeat and low metabolism. Studies have shown that people who exercise tend to get lower resting heart rates than those who are sedentary. High intensity exercises may increase metabolism. I guess I can focus on long slow endurance when I do swimming, cycling and running.
• Fasting does lower metabolism. I don’t eat as frequent anymore. Fasting during the month of ramadhan may help once a year, but I practice intermittent and water fasting more often on other months throughout the year as well. Although I may lose weight on this and negate the size factor later…

Internal factors

• Evolution and Genetics, these is unfortunately the luck of the draw, interestingly, there are genetic therapies being developed, potentially we can identify the genes that are responsible for ageing and extend our life by altering them. Lets see if this happens in our life time.
• healthy immune system, these is also partly genetic, but also on how well we avoid getting sick and in addition recover from them. Medicine has come a long way in assisting us to these very well. Let’s just hope the germs don’t win the biological war against us.
• bigger size, partly genetic, partly nutrition. The bigger the organism the less predator they have, in addition, metabolism can be lower as the body does not need to produce heat too much to maintain body temperature. May also allow bigger animals to eat less per body weight, which lowers the metabolism again. Although my fasting might reduce my weight and thus reduce the size effect.