http://www.scientificamerican.com/ar...tants-fat-diet

Study Finds Exposure to Chemical Pollutants Increases Fat
Rats exposed to high levels of chemical pollutants in fish oil could
not regulate fat properly
By Sara Goodman | January 15, 2010 | 8

FAT CHEMICAL: A chemical found in fatty foods could be sentencing
people to metabolic problems such as obesity and fatigue.

Researchers have for the first time found a connection between
exposure to certain chemicals and insulin resistance, according to a
study published in the online edition of Environmental Health
Perspectives.

A group of European scientists examined whether exposure to persistent
organic pollutants (POPs) contributed to insulin resistance, which has
been increasing around the world. More than 25 percent of U.S. adults
suffer from metabolic conditions stemming from insulin resistance that
include fatigue, obesity and difficulty regulating blood levels of fat
and sugar.

Researchers fed rats a high-fat diet of either crude or refined fish
oil from farmed Atlantic salmon over 28 days. The crude fish oil
contained average levels of POPs that people are exposed to through
fish consumption, while the refined oil contained none. Both had equal
fat levels.

They found that rats exposed to the crude fish oil developed belly fat
and could not regulate fat properly. They had higher levels of
cholesterol and several fatty acids in their livers. Those exposed to
the refined fish oil experienced none of those symptoms.

Researchers said the findings provide "compelling evidence" of a
causal relationship between POP exposure common in the food chain and
insulin resistance, and highlight the need to understand the
interactions of POPs and fat-containing foods such as fish, dairy
products and meat.

How to deal with POPs is particularly challenging because they persist
in the environment for long periods and can build up in animals'
tissues.

The 2001 Stockholm Convention, which the United States has ratified
but not signed, lists and bans numerous POPs from manufacture and use.
The researchers say their evidence reinforces the need to have
international agreements aimed at limiting the release of POPs into
the environment in an effort to protect public health.