hi, disclaimer - i don't do triathlons, nor do i think they're a particularly healthy form of exercise.
before someone chimes in on how fat is a superior fuel, and you can hike everest while in ketosis, i want to say that i think your basic approach is right - stick to primal carbs - but you're underestimating the caloric demands of what you're trying to do.
you will not be able to fuel triathlons on "50-60 grams of carbs and 1300 calories." you need more calories, and you're going to find, most likely, that you need more carbs.
if you enjoy triathlons, by all means, do what makes you happy. if you're just trying to lose weight, i think it's not the best approach.
"dean ornish and dr. davis think the palmitic acid our bodies use for fuel while we sleep is poison if we eat it. zero-carbers like charles washington think the oldest fuel in our evolutionary history – glucose - used by organisms a billion years ago and without which the brains of modern mammals cannot survive for more than a few minutes – is an unnatural toxin if you eat it. both views ignore basic facts of medical physiology and defy evolutionary history." - kurt harris