I haven't worked out in the way you have but I'll add a couple of thoughts.

If you are not counting or measuring I would suspect you are eating less calories than you were before due to reaching satiety sooner on less food. Also you may need more insulin release if you want to build and keep your muscles.

It is unlikely that any of our distant ancestors were as muscular and strong as you can become now through intesnse weight training and powerlifting. In the wild any advantage of the extra strength is outweighed by the cost of aquiring more calories each day to support the extra muscle. Hunter-gatherers would tend to be aerobicly fit and strong relative to their size due to their active life, but in a lean way. For example an Ache tribesman: http://en.wikipedia.org/wiki/File:Ache_Hunting.jpg

This could indicate that a strict paleolithic diet low in carbohydrates is probably not ideal if your aim is to maintain a 400lb+ deadlift. I don't really have any experience to advise how you should eat for that aim though.

I think that the two changes you've noticed: less weight and less performance, might well be separate factors e.g. you haven't lost performance because you've lost weight because it was muscle you were losing through lack of carbohydrate. One would hope that you wouldn't lose masses of muscle if you were eating adequately and training hard.* It's entirely possible that much/most of the explanation is that you've lost weight (fat) and that your performance has dipped independently because of the reduced carbs. It's well known that you can't perform the most intense exercise through burning fat, so you would expect reduced performance if you're not eating adequate carbohydrate at the right time to replenish muscle glycogen, independent of any loss of muscle per se.

On the other hand there may well be merit to the idea that you need more carbs in order to force your body to keep growing. If we assume that carbohydrate signal feasting and plenty and a signal to increase growth (not necessarily a good thing, all thing considered) then it would make sense that carbohydrate would be uniquely efficacious in signalling the body to grow bigger.

This certainly correlates with my own experience, since although I had no excess weight to lose before I went paleo, I did notice a definite drop in performance as I went LC. This applied to all exercise at first (going from being able to run a swift 10km every day while living on wheatgerm, to barely being able to run at all on LC), but once I was fat-adapted my general endurance improved, with the exception of the most intense exertion, which still requires that I've eaten some carbohydrate in the last few days (since the last workout).

*Although this doesn't cohere with my personal experience at all, though it doesn't sound like you have that problem, since whether HC or LC I haemorrhage muscle mass at the drop of a hat.

My background is a bit different in that I am more orientated towards body recompossition than power lifting and only for about 2 years. I can say though that in that time eating Paleo all my lifts have continued to improve. I won't presume to critique you but are you sure that you aren't possibly over training? I'm essentially zero carb eating high fat and moderate protein. I train mostly using Static Contraction using heavy weights once a week with a bit of other work on odd days in between. The trick with that is knowing that if your strength goes down or at least not up then you are not recovered sufficiently and shouldn't be training yet. Other than that if your body seems to do better on more carbs add more sweet potato etc but I don't believe we need many carbs to function well. You may just need to give it a bit more time. Good luck.. BTW I love IFing and prefer training fasted.

As a fellow powerlifter, I would suggest that weight loss (be it muscle or fat) generally leads to a lower total (especially squat and bench) due to the leverages involved. 12lbs is not an inconsiderate loss. Has your deadlift declined in the same way?

Also less stored glycogen means less stored water which of course also leads to inferior leverages (hence the value of "the bloat"!). You could try a big carb/salt load prior a workout or meet and see what happens. Obviously there's a line between performance and health!

But generally I wouldn't worry about the carb intake per se, as strength training and particularly low-rep lifting aren't very costly from a glycogen perspective. You'll easily replace the glycogen from 3 or 4 PLing sessions a week without large amounts (or really any) carbs.

I'm definitely becoming more and more a believer in the Taubesian notion of hormones controlling everything, so providing the stimulus will I believe result in the outcome regardless of how we try to affect it with supplements or diet manipulation. I'm sure that eating to your appetite will over time result in increased strength and muscle mass as if you're providing the stimulus to your body to grow stronger, then your appetite should reflect that need.

You just need to eat more overall. Some people don't eat enough on paleo by just eating to satiety, I know I don't, so you may need to track your calories for a week or two to see where you are at and add a couple hundred or so. You can gain/maintain muscle fine on a high fat, moderate protein, and low carb diet, you just have to eat enough. But if you want to, you can include more dense sources of carbs such as sweet potatoes. Add butter to the sweet potatoes too to add more calories.

One thing you might consider is that people who use carbs in their weight training programs can have more "well-marbled" (think steaks) muscles than without. What I have noticed for myself since going Paleo is that whereas some muscles may not seem as "bulky" as before, their weight-lifting capacity has not reduced. On the contrary, in most cases I find that I'm able to lift a lot more than before I went Paleo. This means that my muscles can produce the same power with a smaller mass, most likely due to reduced intra-muscular fat.

So, it depends on what your goals are. If you're interested in increasing functional fitness (i.e. weight-lifting power and/or endurance), Paleo is the way to go. If you're interested in having muscles that look big, then you might want to put some carbs in your weight training regimen.