The excess weight in an obese person is due to fat. Adipose tissue is over 80% fat, but there is some water and protoplasm found in fatty tissue. When losing excess weight there is very often water retained in the body in that space freed by the disappearance of fat. In some cases it may be several days or even a few weeks before that water gets excreted and the scales show an actual weight loss. This phenomenon is more common in inactive older women than in other age groups who are losing weight.