By Michael Roizen, MD, and Mehmet Oz, MD

Jim Carrey (Lloyd) and Jeff Daniels (Harry) were Dumb and Dumber (or maybe it was the other way around) in the 1994 movie that showcased how ignorance could be bliss -- and mildly amusing. But while it was a hit, it left moviegoers wondering how two characters could be so half-witted. Well, researchers at the Linus Pauling Institute have the answer: By eating a high-sugar, high-saturated fat diet.
We’ve long known artery-clogging saturated and trans fats and inflammation-producing added sugars and syrups damage your cardiovascular and immune systems. Now it’s clear the sugar- and saturated-fat-laden diet of most North Americans slams the breaks on cognitive flexibility -- that’s the ability to adapt to changing circumstance and think on your feet. And there’s more: The study found a high sugar diet also dims short- and long-term memory.
Why are added sugars and unhealthy fats so brain-dulling? The research showed they alter the way your gut bacteria communicate with your brain. Healthy, happy gut bacteria release compounds that act as neurotransmitters, stimulate sensory nerves, and other biological functions. But they can’t run smoothly if there’s a lot of sugar and saturated fat disrupting their fuel lines. In lab-based research, it took just four weeks for saturated fat- and sugar-eating mice to become dim-witted.
So stay sharp. Avoid life-shortening sugars and fats in processed foods as well as saturated fats in red and processed meats. ‘Cause as Lloyd says to Harry: “Life's a fragile thing, Harr. One minute you're chewin' on a burger, and the next minute you're dead meat.”