Any endurance athletes on low carb diets?

I only have anecdotal evidence, so take it with a grain of salt.

I tried low-carb because my then boyfriend was paleo and raved about it. It was awful. My pace dropped considerably. 7 mile runs (which are easy jogs) became torture. It took a lot of the joy out of it for me.

I also do a full glycogen depletion before carb loading for marathons, and the runs I do during that time are extremely difficult. Its not that I can't run, I just can't run fast. Now that I'm venturing into ultras, I've found that Red Vines are my new best friend. I couldn't imagine trying to run 30 miles without copious carbs. I know Pam Smith, the Western States 100 winner, tried to go paleo, and found it to be a "miserable failure" (http://www.irunfar.com/2013/08/how-the-western-was-won.html)

Also, the strict-paleo ex bf decided he would run a marathon because I did. He bonked every run over 15 miles and had a generally bad experience with training. Again, anecdotal evidence. It could be that he just didn't tune his diet very well, but he was following the book "Paleo Diet for Athletes", and it did precisely jack for his endurance.

Clearly my experiences have been negative. Maybe others will be different.

First thing is paleo is not necessarily a low carb diet.

I have tried Paleo/whole 30, for my husband who has tried so much with me. I don't buy all the caveman stuff either. But it isn't a terrible way to eat, protein, fat and lots of veggies. Dairy doesn't agree with me so cutting that out was good for me. I actually felt great, wasn't hungry and didn't miss food. After the inital 30 day trial I continued to loosely follow the diet although no one would ever accuse me of being strict paleo.
The whole 30 encourages you to eat higher carb veggies if you are doing exercise. My diet was not "low carb". Paleo is not necessarily low carb although a lot of people doing it are low carb. I haven't done anything longer than a half marathon, but that did not seem to affect it. I am hardly an elite runner either so take that with a grain of salt.

I also checked out the book Paleo Diet for Athletes as I was aiming for a half Ironman. I'll admit I didn't finish it. But even in the book it says that the paleo diet was not meant for high level endurance athletes and allows for some non paleo ways to increase your intake of carbs and electrolytes if I recall. It was quite detailed, but I never actually tried it myself.

I'm now pregnant so the HIM is out and carbs (mainly bread) are all my body seems to want.