No advantages as it pertains to diving as far as I am aware of.
In other activities, a lower-carb diet is ideal for maintaining a more natural energy metabolic process if you subscribe to the paleolithic diet belief. Also improves insulin response and keeps body fat under control. A nice bonus is that despite using a 5/4/3 full hooded wetsuit I typically don't use any weights. Less things to get snagged while crawling through cracks/holes. One less thing to deal with. Less weight to carry on trips. Less damage to boat decks, etc.
-Paul
Thanks for the response! Being lean definately has it's advantages. Good job on the rescue Paul.