High-Fat Diets and Diabetes
The blogosphere is awash with articles discussing a recent article in Nature Medicine describing one mechanism in which fatty acids may disrupt glucose transport into beta cells, resulting in a decrease in insulin release.
Some sample headlines in the popular press are "Fat disrupts sugar sensors causing type 2 diabetes" (BBC) and "How fatty diets cause diabetes" (Science Daily).
Now, what would you conclude from headlines like that? That fat in your diet will cause type 2 diabetes?
That's not what the cited article said at all!
What the article actually said was that free fatty acids (FFAs) in the bloodstream could hamper glucose transport into beta cells through a mechanism that is too complex to discuss here. FFAs are elevated in obesity.
And if glucose transport into beta cells is hampered, they won't get the message that more insulin is needed, and they won't release more even if blood glucose levels are high.
So if a high-fat diet, or a high-carb diet, or any diet at all makes you obese, then you'll have increased levels of FFAs and you'll be at increased risk of type 2 diabetes.
But if you eat a lot of fat and reduce your carbohydrate consumption and lose weight, then your FFAs will be lower and you'll be at lower risk. It's not the fat in the diet here that is important. It's the obesity.
FFAs are related to fat, but they're not the same. Fat consists of three fatty acids combined with a molecule of glycerol. When you eat fat, it is transported into the bloodstream in particles called chylomicrons and then broken down to fatty acids close to the cells that need the fat for energy. The FFAs are then taken up by these cells and either burned for energy or stored.
When insulin levels are low (for example, overnight), then you'll release some FFAs from fat cells to be carried to other cells to be burned for energy. This is a normal process that provides energy when you haven't eaten for a long time. When you're overweight and your fat cells are insulin resistant, you'll keep releasing FFAs even when insulin levels are high so your FFAs will be higher than normal. And this is the problem addressed in the Nature Medicine paper.
The authors wrote that "a high-fat diet with associated obesity" leads to diabetes and, "Dietary stimuli leading to obesity trigger this process." They did most of the research in mice, which are known to get fat when they're put on a high-fat diet, usually by adding fat to the regular diet. However, even in mice, high-fat diets don't always result in obesity, as noted here.
The science reporters didn't read closely. They just assumed the researchers were talking about dietary fat because so many people have been brainwashed to think that fat is the cause of ill health.
Moral: Don't believe what you read in the popular press. If it's a topic you're interested in, try to read at least the abstract of the original article. With today's search engines, this is usually pretty simple to find.