The Atkins diet hit the scene in 2003. Britney Spears was busy bearing her infamous abs, and everyone, namely me, wanted to know how to get them. I tore through pages of magazines claiming to know her secret, and the general gist was always: Eat steak and crunch your abs like there’s no tomorrow. I didn’t know what low-carb meant at the time, but I quickly fell in love with the idea of it. Bacon, eggs, cheese, steak, rinse, repeat. Lose 12 pounds in two weeks! It was as if all of my food dreams were coming true—and they didn’t involve celery. High-fat FTW!

But starting every day with bacon didn’t quite sit well with me—or my gut. And as much as I loved snacking on cheese, it always left me feeling lethargic. And then my skin got greasier. And then I wasn’t sleeping well. And then I realized I still didn’t have abs. And then I decided, like many others who’d been riding the Atkins train, that it simply wasn’t worth it—and that it also wasn’t working.

Eight years later, I’d completely transformed. I still didn’t have washboards abs, and I was vegan. Bacon was a thing of the past, but fat was very much a part of my present—though this time my focus was on “good” fats. I often ate an entire avocado a day, was fully convinced that beans were indeed a magical fruit (err, legume), and I cleared containers of hummus as if they were calorie free.

Sure, I was filling my body with wholesome foods, and yes, I was sticking to healthy fats, but I still didn’t feel good. My gut acted like a hibernating volcano that would spontaneously erupt, my energy was flat, and my strength was at an all-time low despite my rigorous workout regimen.

Here we are in 2017, and high-fat diets are all the rage, specifically the Keto diet. People are guzzling fat bombs—a fancy and somewhat vulgar name for high-fat, low-carb, and low-protein snacks—like there’s no tomorrow, adding butter and coconut oil to their daily coffee, and replacing burger buns with entire avocados. Talk about a fat (and calorie) fest. I can get down with the supposed brain-boosting benefits of Bulletproof coffee, but eating fat all day, every day? That I can’t get behind.

The old me would’ve hopped on the ketogenic bandwagon without thinking twice—promises of weight loss, high energy, balanced hormones, yes please!—but the current me knows better. Though the perks are tempting, extreme diets often wreak havoc on my body and end in disappointment. I think I’ll pass.

But why are so many people eating so much fat? Is it really healthy to eat two avocados a day? Should we really be putting oil in our coffee? And if a majority of mainstream diets are high-fat, why don’t they work for me?

It was time to turn to science.

The Facts About Fats

As with most wellness trends, it’s easy to get excited before even understanding what’s involved. Juice cleanses cure gut woes? Cool! Putting butter in your coffee makes you smarter? Awesome! But these trends often fall from grace as quickly as they rise.

When it comes to fat, that isn’t the case. Fat, in fact, is pretty fat-tastic (I had to). Here’s why, according to research:

  • It fills you up. Eating fat helps keep you fuller longer. Meaning avocado and hummus are actually super-smart snacks (or additions to a meal).
  • It legit makes you smarter. Not only do our brains need fat to function properly, but consuming fat is also shown to improve cognitive functioning, ward off dementia, and decrease depression.
  • It hearts you. There’s a reason the Mediterranean diet is still oh-so-popular. A study from the 1960s found that people with high-fat diets weren’t dying of heart disease—evidence that debunked the popular notion that fat caused heart complications. Turns out, fat can actually help prevent heart disease.
  • It fights for you. Saturated fatty acids (found in butter and coconut oil) help white blood cells kick viruses and bacteria in the butt. So long, cold season.
  • It keeps you going. Studies show that athletes who eat high-fat diets have increased endurance. Now we know how Forrest kept running and running.
  • It’s nutty how awesome it is. The fats found in nuts have been shown to lower cholesterol; reduce the risk of gallstones, heart disease, and diabetes; aid weight loss; and so much more.

And that’s just scratching the surface. But does that really mean we should start dipping our spoon into a tub of coconut oil?

How Much Fat Is Too Much?

Dietary Guidelines recommend that around 20-35 percent of your daily caloric intake comes from fat. For someone eating 2,000 calories a day, that’s roughly 400-700 calories, or one to two avocados—which isn’t really that much.

Take someone who eats two hard-boiled eggs and half an avocado for breakfast. That single meal is close to half the daily recommended intake of fat. Add a few scoops of hummus, drops of olive oil, a handful of nuts, sprinkle of chia seeds, and a chunk of cheese, and you’re likely way over—even if sticking to small portions.

But guidelines are just that: guidelines. Diets, and health in general, are extremely personal, and what’s right for one person may not be right for the next.

“There’s not one right way to eat,” says Tamara Duker Freuman, MS, RD, CDN. “Paleo can be right and so can a low-fat vegan diet that’s high-carb. They can both produce really good, healthy outcomes.”

And that’s pretty much the case when it comes to fat: There’s no right amount. It’s all about finding what’s right for you.“The data and the science suggest there’s a wide range of fat intake that can be considered quite healthy,” Duker Freuman says.

But not so fast: Not all fats are created equal. There’s a big difference between the fat in bacon and butter (saturated fat) and the fat in avocado and olive oil (monounsaturated fats). And while the benefits and risks of eating saturated fats will never cease to be debated, there are clear downsides that come with eating high-fat.
  • It accelerates aging. Turns out fat bombs aren’t so great for our liver—or our overall longevity.
  • It encourages overeating. Eating fat has been shown to increase overconsumption, and in some cases, lead to obesity.
  • It’s not so great for our guts. High-fat diets can cause inflammation in the intestines, and eating high amounts of saturated fat can even lead to inflammatory bowel diseases.
  • It has a bone to pick with us. People with high-fat diets, women in particular, are shown to have lower bone density, which increases the risk of osteoporosis.

Where Do We Draw the Line?

“Somewhere between 40-80 percent is probably too much,” Duker Freuman says. “But we don’t really have the science to tell us what that exact number is.” And that’s the other thing: Some of these high-fat diets are so new that many of them haven’t been adequately studied.

“I think some of those ketogenic diets are too much,” Duker Freuman adds. “People are getting 80 perfect of calories from fat. There’s no great data in adults who are following that diet. We have no idea what’s going to happen them cancer-wise or disease-wise.”

The Takeaway

There are benefits and downsides to eating high-fat. There are healthy fats, and there are less-healthy fats. As with most diets and ways of eating, the best thing to do is to figure out what’s right for you.“We need to move the conversation away from the idea that there’s one right amount of fat to eat. There’s not,” Duker Freuman says. “There are a lot of healthy and different diets out there.”

When it comes to fat, try and stick to healthier ones and up your intake slowly. It’s all about listening to your body. (Though it’s probably safe to say that going hard on fat bombs for breakfast, lunch, and dinner may not be the best for anyone.)