Anyone who has been on a diet can attest that it seems the more weight you lose, the harder it gets. That’s not in your imagination. It’s in your metabolism.

Our bodies are wonderfully adaptable, so the more weight we lose, the more our metabolic rates drop—meaning we burn fewer calories.

What if there was a way to tip the metabolic scale back in our favor? Researchers at Cedars-Sinai are seeking to do just that by changing fat cells that store energy into fat cells that burn energy.

"Even the winners of big weight-loss shows like The Biggest Loser—with all those high stakes—regain the weight eventually," said Deborah Clegg, PhD, a researcher in the Division of General Internal Medicine and Department of Biomedical Sciences. "So there must be more to this than just diet and exercise."

For a long time, scientists believed there were two kinds of fat cells: white "storage" fat cells and brown "baby fat" cells. Brown cells keep our bodies warm by converting chemical energy to heat, burning calories along the way.

Brown cells are rich in mitochondria, the components of our cells that burn energy. Lean people tend to have more brown cells.

Now, researchers have found a "beige" fat cell: a cell with more calorie-busting mitochondria than a white cell, but not as many as a brown cell.

Low temperatures can transform white fat cells into beige ones—but it’s not a sustainable solution for weight loss. Even if someone could tolerate staying very cold for long periods of time, the body would adapt by using fewer calories, so the weight-loss benefit would be only temporary.

"Now everyone is off and running to see if there are drugs we can use, stuff out there we can do that will transform white fat cells into beige fat cells without having to expose people to cold," Clegg said.

Read: Q&A: Metabolism

They found women have more brown cells than men, and Clegg and her team believe estrogen plays an important role in the difference. They’re adding estrogen to white fat cells to induce them to turn beige.

So far, it seems to work.

They’ve been working to nail down the exact mechanisms behind that change. Estrogen works on a number of receptors in our cells. Some are on the surface of the cell, while others are in the nucleus.

Receptors in the nucleus drive the creation of genes, so working with them could be riskier, Clegg says.

Happily, the data so far indicate that the transformation comes from the interaction between estrogen and receptors on the surface of cells.

"That’s a druggable target," Clegg says, "and you don’t have to worry about causing any changes in the cell DNA."

"It could open up a world of possibilities to change the white cells to beige cells in a healthy, safe way."

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