Every so often brands change their image/designs to keep up with time. This is allows them to keep up with the trends and appeals more to their target audience Me personally i think they have changed it for the best, better font but has kept the iconic colour scheme so people will automatically know its pepsi.
Pepsi-Normal white stripe
Diet Pepsi-Skinny white stripe
Pepsi Max-Wide white stripe
Here you can see that Pepsi has changes their design to match each product. There are images on the web converting the icon into a fat man bending, so when ever I see this design it reminds me of this.
Its a fun, playful design and gets the public/designers involved and creates fun designs like this. Was pepsi thinking of this when creating a face life to the brand? So if i drink the diet pepsi will i have a smaller belly? Hopefully i would.