A Harvard nutrition expert tells us why we should eat more fat

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We've been told for decades that we shouldn't eat too much fat. Remember how it was on the top of that food guide pyramid you probably saw in elementary school? 

For "bad" fats, like trans fats, this is true. 

But scientific evidence has been growing that this advice was misguided, and that low-carb, high-fat diets can be beneficial. 

One proponent of this worldview is Dr. David Ludwig, a Harvard Medical School nutrition and obesity expert, who talked to Tech Insider about what scientifically sound dieting looks like.

His book, "Always Hungry?" outlines an evidence-based eating plan that focuses on what you eat, not just how much. In it, Ludwig proposes an alternative hypothesis for why his plan works that he's based on scientific research, though it is still not widely accepted in the field. 

When we eat processed carbohydrates, like white bread or cookies, the insulin levels in our body skyrocket. Ludwig's idea is that this spike in insulin makes our fat cells suck up calories and hold on to them. With so many calories being stored in fat cells, he says, the amount of calories in the blood are lower, so the brain thinks that the body is hungry. 

And one of the fastest ways to get more calories in the blood is to eat more simple, processed carbohydrates. So we eat them — and then we crave more. It's a vicious cycle, Ludwig says, that can lead to a slowed metabolism, and eventually obesity.

How can we break this cycle? By cutting carbs — especially processed ones with a lot of added sugar — out of our diet, and eating more fat. 

"The best way to [break the cycle] is by increasing the fat that you eat a lot," Ludwig said. "That helps you displace the processed carbs, and it actually creates a luscious, satisfying diet. Every chef knows that a great way to make food tasty is with a lot of fat. And this way, you get to do that without the guilt." 

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Despite what many people believe, studies have found that replacing the carbs we eat with fats can actually lower heart disease risk, and decrease blood pressure. 

Some of the best high-fat foods that Ludwig recommends eating are avocados, olive oil, and nuts. Of course, these fatty foods have to be balanced out with other healthy, whole foods like fruits, vegetables, and protein. 

But it's nice to hear that fat isn't as scary as we've been told. 

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