For years, the “experts” on nutrition have been telling us to shun fat and load our plates with carbs instead. They’ve told us that butter and avocados and coconut oil are bad, and that cereal and sandwiches and pasta are terrific. 

What’s the result? We’re experiencing epidemics of obesity and diabetes, both caused by overloading our bodies with sugary carbs and depriving them of crucial fats. If you’ve followed my blog or you’ve read my books, none of this is news to you. But here’s something you might not know: There are even more risks in low-fat diets that you may not know about. Here’s a look at four of the biggies.

Depression and suicide

For decades, studies have shown that low-fat diets are associated with higher rates of depression and suicide, as well as higher rates of aggressive behavior.

To me, that’s no surprise at all. If your brain doesn’t have enough fat, the neurotransmitter serotonin can’t do its job, which includes keeping you happy and helping you curb your impulses. A brain that’s starved of serotonin is an unhappy, out-of-control brain, and that’s a prescription for trouble.

Hormonal Imbalances

Fats are building blocks for your hormones. If you don’t get enough healthy fats, you’ll throw these hormones out of whack, leading to everything from rapid weight gain to “brain fog” to thinning hair. What’s more, a low-fat diet may also increase your risk for infertility.

In addition, a low-fat diet—which replaces fats and protein with carbs—makes your insulin levels spike, causing you to lay down belly fat. Belly fat cells are estrogen factories, and if they crank out an excess of this hormone—a condition called estrogen dominance—you’ll gain weight like crazy, you’ll experience bloating and mood swings, and you’ll be at increased risk for breast cancer.

Alzheimer’s disease

When you eat a low-fat, high-carb diet, your body has to churn out large amounts of insulin. Over time, your cells react by becoming insulin resistant, meaning that they get less responsive to insulin’s message. In effect, they slam the door on insulin and the glucose it’s trying to deliver.

This is very bad news, because a recent study shows that in addition to putting you at risk for diabetes, insulin resistance can raise your risk for Alzheimer’s disease. This study found that insulin resistance reduces the amount of blood sugar in areas of the brain most vulnerable to Alzheimer’s disease, meaning that these areas get less “fuel.”

“If you don’t have as much fuel, you’re not going to be as adept at remembering something or doing something,” study coauthor Auriel Willette says. “This is important with Alzheimer’s disease, because over the course of the disease there is a progressive decrease in the amount of blood sugar used in certain brain regions. Those regions end up using less and less.”

The researchers found that even people with only mild insulin resistance may be at higher risk for dementia. And if that doesn’t get your attention, they say that insulin resistance may harm your ability to think at any age.

Nutritional deficiencies

Research shows that if you skimp on fats by topping your salads with a low-fat or fat-free dressing, your body can’t absorb important phytonutrients called carotenoids. You also need fat for your body to absorb vitamins A, D, E, and K. So you could be loading your salads with fabulous fruits and veggies and still not be getting the nutrients your body needs.

— If you’re still having trouble rejecting the “fat is bad” myth, I hope these findings will encourage you to reconsider. The truth is that fat isn’t bad—it’s necessary! So add a dose of healthy fat to every meal in the form of fatty fish, coconut oil, olive oil, avocado oil, nuts, or clarified butter. In addition to trimming you down, that fat will do wonders for your brain and body!

Keep thinking Big and living BOLD!