I did his Slo-Carb diet for a long time, and what I learned with that diet, as with all diets, is that the body eventually adapts itself to what you're doing, and you just hit a brick wall in terms of continued results. The fact of the matter is that your body doesn't want to be lean. It wants to survive above everything else, and maintaining a good source of usable energy in the form of stored fat is how that happens.
So once you get to a relatively low bodyfat level, you have to trick your body and temporarily force it to conjure up metabolic hormones that it wouldn't normally make available.
The word of the day - attenuation. Though not completely correct, but similar in concept. Repeated exposure to the same stress generates an increasingly smaller response from the body until there is none. The body is then fully adapted to that particular stress.
You can't continue with the same program forever, whether its diet, exercise, or sport-specific training. The body needs new stress to adapt. You have to continually shock your system.
Marathoners, once they establish their endurance base, will not see any improvement in their performance if they keep doing LSD of 60-120 miles a week. At some point, they'll need to dial back the mileage, and start doing intervals of varying distance, rest periods, and reps. Same with lifters - can't continue lifting using the same exercises, weights, and reps, and expect continual improvement.
Death, taxes, and change are the constants of life...