Congestive heart failure is by no means the only thing that causes massive increase in bodily fluids. Several categories of medication cause weight gain that is almost entirely fluid based, not fat. And basically anything that knocks your kidneys or liver down or out leads to fluid building up throughout your body.
Water weighs a lot. There is a story (in one of the callout boxes where individuals tell a weight related story of their own) in _Body of Truth_ about a woman whose father retired and gained a bunch of weight. The doctor told him to lose the weight and didn't do any tests. Eventually, he was diagnosed with hemachromatosis and died. The woman blamed the doctor who he saw when he gained a bunch of weight and became almost unable to eat anything because he felt so full all the time, for not catching it. Abdominal fluid retention, tho, seems to be a late stage in hereditary hemachromatosis, so it's less clear to me whether it's worth blaming the doctor. Was the doctor incompetent? Sure! Was dad gonna die of this thing anyway? Probably. OTOH, maybe he could have lived years longer with proper diagnosis and treatment.
In any event, with medication, congestive heart failure, hemachromatosis and countless other processes leading to abrupt weight increases that are WATER NOT FAT, I cannot for the life of me understand medical practitioners who insist that weight is about calories in and calories out (in the form of activity). Fat, even body composition may be, but weight is NOT. And the differential diagnostic trees memorized by every doctor include countless instances of ask about sudden change in weight as one of the signs/symptoms of a disease process.
Given that Dr. Atkins _described explicitly_ in his book advocating his diet how it first caused weight loss through forcing the metabolic use of glycogen stored in muscle (thus resulting in the dieter peeing out all the water stored with the glycogen), you would _think_ that everyone would factor in this whole water thing by now. But all the evidence indicates that when people start using scales, they act like water retention isn't a real thing.
I don't get it.