There are plenty of places on the body where you definitely don't want fat building up.

Hello, gut.

But there's one place you want as fat as can be, and that's right inside your skull. Your brain is actually 60 percent fat -- and the most critical fats of all when it comes to brain health are the omega-3 fatty acids found in fish oil.

Now, a new study confirms just how important those fats are for your thinker: People with the lowest levels have aging, shrinking brains and problems remembering what they had for breakfast.

Since the most prominent fat in your brain is DHA, the study of 1,575 dementia-free seniors also finds that it's the most important one for brain health. The 25 percent with the lowest blood levels of DHA had the smallest brain volumes.

And, yes -- when it comes to brains, bigger is definitely better.

Younger is better, too. And while you can't turn back the clock, your brain can get old before its time -- and seniors with the lowest DHA levels had brains that seemed two years older, according to the study in Neurology.

That's what's going on inside the head.

Out in the real world, seniors with the lowest omega-3 levels did worse on just about every test thrown their way -- including tests on visual memory as well as executive functions such as problem-solving, multitasking, and abstract thought.

Along with charging your thinking cap, omega-3 fatty acids can also help slash your risk of heart problems, stroke, macular degeneration, and more. They can even lower your risk of gum disease.

But let's stick to the brain today.

In addition to those omega-3s, be sure to get plenty of B vitamins. Studies have shown that seniors who get high levels of B6, B12 and folate have bigger brains, better memory, and more overall protection from dementia's top risk factors.

You can read more about that B vitamin and dementia link right here.

Meats tend to be richest in B vitamins, but the best way to get what your brain needs is with a quality B complex from a trusted vitamin maker.

Similarly, you can get omega-3 fatty acids from a diet rich in fatty fish -- but since most people don't eat nearly enough salmon, herring, and anchovies, add an omega-3 supplement to your shopping list if you're not taking one already.

For one more way to power up your grey matter, keep reading.