Fat cells number remains unchanged despite weight loss.  

Adipose Stuffed Animal

In weight loss, the number of fat cells remains unchanged even in weight loss.  Even after massive amounts of weight loss, the number of fat cells remains constant.  In fact, fat cells remain constant after childhood and adolescence.  

As children and adolescents, we increase out fat cell number as we age, but one it has stabilized as a young adult, fat cell number remained unchanged unless you have fat cells removed like with a liposuction surgical procedure. 

So how do we gain and lose weight without increasing and decreasing the number of fat cells?  Ultimately, we just shrink or enlarge the cells.  Adipose or fat cells are nothing more than cellular bags in the body that store fat.  They increase and decrease cell size by adding more to or reducing the amount of fat stored.  In other words, degree of leanness or obesity results in increased contraction or expansion of the cell respectively.  

The bottom line: Weight loss results in a decrease in the size of fat cells and not a reduction in the number of fat cells.