Estrogen and Exercise Promote Leanness in Similar
Ways By Rosalie
Marion Bliss October 21, 2005
A common hormone has been found to help the body use fat and glucose
as energy in the same way that exercise does.
Agricultural Research Service-funded
scientists will report the findingsbased on animal studiesin next
weeks issue of the Journal of Biological
The study, led by physician
Greenberg and colleagues, actually reveals a number of novel mechanisms by
which estrogen promotes a reduction in fat cell size and fat tissue mass.
Greenberg is director of the
Metabolism Laboratory at the
Mayer USDA Human Nutrition Research Center on Aging at
Tufts University in Boston, Mass.
Estrogen is an important hormone in both women and men. It activates
pathways that regulate metabolism and also directly regulates the expression of
certain genes. The results shown were based on providing half of a group of
laboratory mice that had no ovaries with a placebo pellet and the other half an
estrogen pellet for 40 days. The mice were fed equal amounts of chow.
In the mice, estrogen replacement was found to reduce lipids, or fats,
by promoting the use of fat as fuel. The three mechanisms for the observed
action include: inhibiting fat storage in liver, muscle and fat tissue;
activating the pathways that promote burning the fat in muscles; and breaking
down stored fats used for energy reserves in fat cells.
When estrogen was present in muscle, liver and fat cells, the
expression of genes that control manufacturing and storing fat was reduced, and
the expression of genes that promote burning fat in muscle cells was increased.
Scientists long have known that fading estrogen levels lead
postmenopausal women to accumulate more fat and sometimes develop insulin
resistance or diabetes. The study demonstrates that estrogen may reduce body
fat in animals and may explain some of the reasons behind the association of
menopause with increased risk of insulin resistance and diabetes, according to
ARS is the U.S. Department of
Agricultures chief in-house scientific research agency.