New study explains why different types of fat have different health effects

Saturated fats activate a key metabolic pathway associated with the development of type 2 diabetes, while polyunsaturated fats like omega-3s shut this pathway down, according to a new study from a team of researchers from the University of California, San Diego.

Not only do the findings provide an answer to a question that has plagued scientists for years - why are some fat beneficial while others are harmful? - it could also lead to the development of new medications that prevent a person from becoming obese and developing type 2 diabetes, the researchers said.

For decades, researchers have known that individuals who eat high levels of saturated fats tend to develop type 2 diabetes and other chronic diseases at high rates, while those who consume more polyunsaturated fats tend to have better cardiovascular and metabolic health. However, given the fact that both types of fat are structurally somewhat similar, the reasons behind the different health effects were unclear.

After studying the impact of various types of fat on cultured cells, the researchers found that saturated fats activate a set of cellular receptor sites known as Jun kinases. Activation of these pathways has previously been linked to the development of chronic disease, such as type 2 diabetes. Yet this is the first study to show that saturated fats play a direct role in their activation.

The study also revealed that polyunsaturated fats deactivate the receptors and prevent them from being switched on in the future, which helps explain the metabolic and cardiovascular benefits of these nutrients.

The researchers said the findings could have significant implications for the prevention of obesity and type 2 diabetes in the future.

"These findings not only explain the long-standing enigma regarding the differential health effects of saturated and unsaturated fatty acids," said lead researcher Michael Karin, PhD. "They also provide improved tools and a mechanistic framework for the potential development of dietary supplements to treat obesity, estimated to be worth billions of dollars per year."

Seafood is one of the best sources of polyunsaturated fatty acids. Salmon, tuna and mackerel all have very high levels of omega-3s. Many plant foods, including nuts, also have a number of beneficial fats. A diet rich in these nutrients has previously been shown to reduce a person's chances of developing type 2 diabetes. The new study helps explain why that is.