OK - I am still on the muscle/fat thing.
I look at the people whom I consider blogging friends who have lost significant amounts of weight. Did they lose more fat or gain more muscle to achieve what they have done?
Was this accomplished by eating less and moving more?
This brings me to the moving more part. We do aerobic activities for the calorie burning effect, endurance, and some toning - mostly lower body. While there is some muscle building I would say not a whole lot - those who wish to gain muscle must do some weight lifting or exercises that use their body weight as the resistance such as planks, pull ups, push ups, sit ups, and squats. There are many more but these are the basics for body weight exercises I would say. My good friend Norma, who used to blog and I miss her terribly, has just told me her trainer told her that a woman who is eating clean, not using any steroid type "helps", and doing exercises for building muscle could expect to perhaps gain about 5 lb. a year in muscle. There are variables of course but for the sake of argument let's even say 10 lb. in a year. The work it takes to do that would certainly burn bunches and bunches of calories. While gaining that 10 lb. of muscle in a year a woman could very realistically expect to lose 80 - 100 lb. - maybe more. There are variables here of course as well - but again - I'm arguing. Norma has taught me well. :-)
So - my point is, that unexplained weight gain in one week is not because of increased muscle mass. There are many other explanations. AND - we might not know the reason, ever. If it takes a whole year to gain my argument of 10 lb. of muscle - in one week - let's see 10 lb. = 160 oz. divided by 52 = a little over 3 oz. - less that 1/2 cup of water.
Losing fat uncovers the muscle. Think of it friends, we all have a 6 pack under there. If we do the exercises and get the fat off of them - voila! We have burned calories building the 6 pack while uncovering those babies at the same time.
We lose fat a lot faster than we gain muscle.