How? They located a gene that controls the expression of certain chemicals in the body related to metabolism and energy balance. They then altered the gene so that it's expressed less. In fact, they changed it so the mice produced 25% less of the chemicals involved. In doing so they effectively changed the balance of energy and metabolism in the body.
From here they saw that the mice managed to keep their brain power working into their newly found old age. However, some of the consequences that wouldn't be quite so desirable we're the impact on bones and the immune system. These genetically altered mice had less dense bones (similar to osteoporosis) and were less able to fight infection as they aged, highlighting immune system weakness.
Let us know what you think in the comments section. We believe that certain improvements, say immunity to disease, would be fantastic but where o you draw the line and who gets access?