Doctors nearly unanimously agree that eating foods loaded with saturated fats — such as butter, cream and pork in all its wondrous manifestations — can cause heart disease, obesity and diabetes. Conversely, foods with unsaturated fats, such as olives and salmon, can have the opposite effect.

Yet no one has known why, until perhaps now. As reported in the Sept. 30 issue of the journal Cell, researchers from University of California, San Diego (UCSD), found that saturated fat literally clogs cell membranes at the molecular level, causing abnormal cell signaling that ultimately throws basic metabolism out of whack. [7 Foods Your Heart Will Hate]

If the researchers are right — that is, if their work on mice proves true in humans — then they envision a new class of dietary supplements or pharmaceutical drugs to reverse the effects of a high-fat diet.

Knowledge congealed

Saturated fats tend to be solid at room temperature. They contain fatty acids that are saturated, chemically speaking, with hydrogen atoms; the carbon atoms are bonded to as many hydrogen atoms as possible. Unsaturated fats contain fatty acids with a lower ratio of carbon to hydrogen.

For over a decade researchers have known that saturated fats somehow activate enzymes associated with developing insulin resistance (a precursor to diabetes) and atherosclerosis, or clogged arteries. Unsaturated fats can block these enzymes within our cells. The enzymes, called Jun kinases, work at a subcellular level.

Building on this knowledge, a UCSD team led by Michael Karin speculated that something in cell membranes must be able to differentiate between saturated and unsaturated fats, activating or deactivating Jun kinases. In their new study, the team ultimately identified yet another enzyme, called c-Src, which resides within a cell membrane.

So, saturated fats apparently smother and push c-Src deeper into the cell membrane, to regions that are more rigid. The c-Src accumulates here and turns into an activated form that then triggers Jun kinases to start working — setting into motion the chemical reactions behind insulin resistance and circulatory disease.

Unsaturated fats, in contrast, block c-Src aggregation and thus prevent the whole cascade of troubling chemical signaling.

One pill makes you smaller

For scientists, the findings provide a new model for how cell membrane composition can trigger different signaling cascades. For non-scientists, the findings might mean that you can have your saturated fat and eat it, too.

Consider how polyunsaturated fatty acids such as EPA (also called eicosapentaenoic acid) and omega-3s are available in a pill form, more or less in their natural state. These aren't miracle cures, but they do help some people lower their blood cholesterol (or, blood fat) levels. With a better understanding of why unsaturated fats can have protective effects, doctors might be able to identify more potent EPA-like molecules, Karin said. These molecules, delivered in a pill, could reverse the negative cycle put into effect by diabetes and other chronic disease.

If popping a pill irks you, or if you can't wait a decade for a pill to hit the market, you can always switch to a diet that strives to reduce saturated fats. This means eating less meat and more vegetables and whole grains.

While some doctors recommend eating so-called lean cuts of meat, the very existence of lean meat necessitates the existence of fatty meat, which someone else, someone likely poorer than you, will eat. And that's no way to feed a planet.

Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His column, Bad Medicine, appears regularly on LiveScience.