I've been zero-carb since September 2009, so a few months shy of two years, except for a brief (3 week, maybe?) foray into veggies around Thanksgiving in 2010. My experience is that bowel movements are much easier and quicker when zero-carb, even compared to very low-carb. I do eat a pretty high-fat diet (65-75% of calories as fat, last time I did the numbers), so that may have some bearing. Sometimes I skip a day, and that doesn't seem to be a problem at all. Mostly I'd say the absence of fiber results in an absence of bulk in the stool, and an absence of gas -- seriously, no farting, ever. :)

Depends wholly on the amount of fat content in my diet. For a few weeks I actually bothered with fitday and logging to get a general idea of where my breakdown was. When I exceeded 70% of my daily calories from fat, I would go twice a day and the onset was pretty sudden... "OMG TIME TO CRAP!"

However, under that ratio and still keeping carbohydrates at 10-12% of daily intake, and I would get a "heavy" feeling in my low gut, that would be exacerbated by a cup of coffee or a big meal... that would let me know about an hour ahead of time that I needed to poppasquat soon.

Early on in following LC I was troubled with constipation. After reading Perfect Health Diet by Paul Jaminet I added in some starch (up to 1/2 cup of white rice or potato)several times a week. The starch made my bowel efforts easier and more regular because it stimulates mucus production in the colon. I also eat a small salad several times a week which adds some bulk to my stool. I hope things work out for you. I've never felt better and have been eating LC high Fat for about 6 months.

For me, my bowels were looser for a few weeks, then normalized.

I ate literally zero plant matter for three months. Before that I was WAP for three years and then paleo for about six months just so you know. I had a morning bowel movement every day of the three months, no worries. They were indeed smaller I think. Makes sense I guess, I was exercising a lot and pretty active. Meaning that I think my body just absorbed more of the animal product and had less waste material. Never had a single problem. I did eat a good amount of fat,usually animal fat and coconut oil. At times I did a lot of butter on shrimp and I had a bit of steatoria. Wasn't the end of the world, though.

I do NOT recommend eating solely animal products for times longer than a few days, though. Just so we're clear. Any athletic endeavor you engage in will prolly suffer. Even being a longtime fat-burner. I haven't been a sugar-burner in years but carbs are stillcarbs and fuel athletic endeavor very well.