A body of water
In adults, the healthy body is made up of the following (approximate values):
Skeleton - 14%
Water - 60% (this is much less in obese patients)
Skeletal muscle - 42% in males, 36% in females
Lipids - 12%
Protein - 20%
Skin - 15%
Blood - 8%
Bacteria - 1%
Now, of course, this will add up to more than 100%, that is because there is an overlap between these.
When dieting, one of the first things that can be lost from the body is water and water fluctuations in terms of percentage in the body can mislead the unwary in terms of weight loss and gain.
An empty and full bladder can make up to 1kg difference (depending on the size of your bladder!) as can the contents of your colon. Using laxatives and diuretics can create the illusion of weight loss, but in fact, what is lost from the body is water. Inappropriate laxative use can have a damaging effect on the body and chronic misuse can seriously damage the digestive tract.