September 23rd 04, 07:10 PM
"Ed" <[email protected]
> wrote in message >...
> "August Pamplona" > wrote in message
> > In ,
> > Lyle McDonald > typed:
> > Well, duh! It probably just means that when people get fat, their
> > fat cells divide and when they lose fat, their fat cells shrink because
> > their increased numbers are retained (unless they die off --which either
> > doesn't happen or happens very rarely).
> Fat cells do not divide. You are born with all the fat cells you will ever
> have. They simply grow and shrink. The only way of reducing your fat cells
> is by lyposuction. However if you get fat again the body will make your
> remain cells that much bigger but it can not produce new ones.
You are wrong. Mature (differentiated) fat cells can not divide.
However, adipocytes (fat cells), just as all other cells, have a
finite size of expansion (hypertrophy). Although an increase in
adipocyte size occurs before an increase in the number of adipocytes
(hyperplasia), the latter does indeed occur. When adipocytes reach a
critical size, growth factors released from the enlarged cells and
possibly nearby cells (fibroblasts, etc) trigger proliferation
(division)and differentiation of preadipocytes (the precursor cells of
mature adipocytes). Adipocyte hyperplasia in humans is more common
after birth for a short period of time.
I suggest you read a recent review of adipocyte cellularity/biology.
"Even at the adult stage, the potential to generate new fat cells
persists. It has been demonstrated that fat cell number can increase
when rats are fed a high-carbohydrate or high-fat diet (67, 68, 176).
Increase in fat cell number is also observed in severe human obesity.
However, the relative contribution of fat cell size and fat cell
number to human adipose tissue growth on nutritional stimulation
remains to be clarified. Regardless, early differentiation markers of
adipocyte differentiation can be detected even in adipose tissue
derived from very old mice (138). Moreover, fat cell precursors
isolated from adult WAT of various species, including humans, can be
differentiated in vitro into mature adipocytes (21, 58, 98, 104, 160,
213, 264). The potential to acquire new fat cells from fat cell
precursors throughout the life span is now undisputed."
Excerpted from: Understanding Adipocyte Differentiation. F.M.
GREGOIRE. PHYSIOLOGICAL REVIEWS. Vol. 78 No. 3 July 1998, pp. 783-809.
Hope that helps.