I also started my carbo-loading regime. When it comes to carbo-loading I am a traditionalist and I prefer the old method of not eating carbs (or very little) for a week and then eating two days of almost nothing but carbs.
I have used this method four or five times now and it always works for me. It has several other advantages too. One is that I lose weight. Even though I exercise less, I can eat as much as I want and I never feel hungry either. That is the best part. It seems likely that much of the weight loss is water and much of that is probably due to glycogen depletion. The weight loss is not my aim, but weight control is. I don't want to gain weight now.
The trouble with high carb diets is that you tend to feel hungry all the time. It is not a big problem when you work out a lot because you need the calories. But when you taper it can be really hard and I know quite a few people who gained several pounds during their taper. I tend to lose weight. Usually several pounds.
There are two bad effects: 1. I develop a slight nausea by day two -which may be what keeps me from over-eating, and 2. I do feel sluggish after about two days.
There is one so-so effect: I develop a real craving for carb rich food. After several days, bread, pasta, and other items start looking really good. But that is OK, by Friday I will be able to eat all the bread I want.
In addition to the carbo-loading, I also cut back on all fruit and veggies two days before the race. That too is quite beneficial in my experience. It makes it so you don't need potty breaks and it tends to avoid stomach upsets too.
I did a simple 30' fit test today.
First I ran 2 mi. to warm up and then I tried to hold 9 mph for 30 minutes (4.5 miles). It is what I did last year before the marathon. Unfortunately, this year I was only able to hold 9 for 4 miles or 26.66 minutes.
It is possible that the heat in the exercise room got to me. The club remodeled the room last week and put the treadmills much closer together to enable TV viewing. They also removed all the fans. Both effects combine to induce more heat stress.
The heat could explain some performance loss, but most likely is that I am not in as good a shape as last year. I finished off with another mile to make it 7 total.