I am relatively new to Paleo, but I do some IF that kicks me into Ketosis.

For example, yesterday I did almost a 24 hour fast not eating 7pm to 7pm except a couple of slices of salami. When I first started Paleo, which was the same time as starting CrossFit, I was seeing 1 pound per day weight loss. This dropped off after 10 days, but when I throw in a little IF, I see weight loss pretty similar. (Started at 202 in Nov. 2011 and I am currently 180 heading for 170). I have good energy through the day, and I do a morning workout so I am not too hungry when I workout.

Some people say that ketosis eats muscle, but my anecdotal experience is nice gains in strength doing the same workouts from Dec. to Jan. during which I was in and out of ketosis. Point being that if it was that detrimental to muscle I wouldn't expect to be getting better at my lifts.

Also, I notice that even though my weight isn't changing alot (muscle is heavier than fat right?), my leanness is changing and I see a difference there when I get Ketosis to kick in after a couple of days.

My last point, is that it doesn't take much to get out of ketosis, which is why I do IF. I follow strict Paleo almost 100% (had a little dark chocolate that had sugar in it last night). If I am in Ketosis and then have a bunch of fruit, then it takes a day to get back into it. Also, using Ketosis Strips tells me that I am generally only in the moderate range of 40-60 on the ketosis scale which is mostly impacted, I think, by fruit consumption.

If water fasting, I would not do any real physical exercise, and get plenty of rest, from personal experience. It does jump you into ketosis pretty fast.

I think the main benefit of starting with a fast will essentially be psychological. I would expect it would make it easier to break with previous habits and cravings, to focus on the true purpose of food. It also makes it a lot easier to cope whenever you have doubts with the new diet.

As to the exercise, I would say it depends on your current level of fitness. I keep doing yoga, bodyweight exercises as well as high intensity cardio, sprints, sports and heavier weights while fasting. My strength doesn't suffer, but depending how long you go you may find a shortness of breath in sprints particularly as essentially it becomes an aerobic exercise. You'll also want to take it steady when standing etc. particularly if in a hot room as your blood pressure will probably be affected. If you're dizzy all the time or struggling then you probably want to exercise less and sleep more, but if you're careful you can probably find that limit yourself. Of course, if by a 'short fast' you mean 16 hours then this is unlikely to be relevant.

It is the other way around; there is a benefit to ketogenic dieting before fasting. Either way you'll go ketogenic, but if are definitely ketogenic before you start fasting (and you've had a lot of fat + nutrition to hold you over during the fast), then the fast will not be too troublesome because there will be no blood sugar crash.

If you fast first you'll get the blood sugar crash during the fast and you may cave into the cravings.

Also, your training regimen means you do need more calories and probably some carbohydrates, especially after exercise, to replace glycogen stores.

Make sure you are supplementing with Magnesium (Citrate, Malate or Glycinate.) Most folk are deficient and you will really feel the effects of the deficiency when you fast or go vlc. You don't want any dizziness when doing Bikram yoga!

Also, if you are going vlc & fasting to get rid of your sugar cravings, make sure you are 100% Paleo first.

Gluten seems to trigger cravings in some people and if you are only "mostly" Paleo, this may be the problem, NOT the amount of carbs you are eating.

I am in my forth consecutive day of a 23 hour fast where Bikram is the last thing I do before I eat. I have been paleo for a few years now and fast regularly, I just decided this week to keep fasting each day after Monday's 23 hour fast. I always fell great when I fast and this week is even better. Oh, I am sticking to a Whole30 diet too, started on Jan 2nd. I also mix in the pushups, pull ups and other body weight exercise, everything together totally puts me in the zone. Now that I feel so well I am reluctant to stop the fasting but probably will when the weekend gets here. bikram seems best for me when in a fasted state. Go for it and see how you feel. KB

I did bikram yoga for the first time this past Monday...I was STARVING almost immediately after the class ended. 8)

My guess is, just like any other activity, once you get used to it a fast would not be a problem. Sounds like you have been doing bikram for a while, so I would assume you would be fine. Just go by how you feel.