Top Nutrition Expert Shares The No. 1 Mistake He Sees In American Diets

“I don’t think I’ve ever seen anything like it in the last decade, as far as food trends go,” Spector tells Fortune. 

The problem with this way of eating, Spector says, is that people often choose ultra-processed foods advertised as high-protein and low-calorie, missing out on fiber-packed, gut-healthy plant foods.

And that leads them to make what Spector calls the number one mistake in nutrition: focusing on calories over quality.

“Most people think that you can pick a good diet if it’s low in fat, low in calories, and high in protein, and nothing else matters,” he says. That kind of mindset is not only inaccurate, but it could be harming your health, according to Spector.

Don’t fall into the protein trap

Spector says our perception of the importance of protein has been warped, as more foods are marketed as high-protein, and social media pushes protein-packed recipes and diets.

“The food companies love adding protein because it’s dead-cheap, and it’s following this huge marketing wave,” Spector says. But protein is just one component of your diet.

“We’re often failing in nutrition to think about…what does your plate look like,” Spector says. What it should be about, he says, is fiber.

“The truth is, 90% of Americans are getting more than enough protein,” he says, “and 90% of Americans are fiber-deficient.”

Several studies show that higher fiber intake can lower your risk of death from cardiovascular, infectious, respiratory diseases and cancer. One study found that for every 10-gram increase in daily fiber intake, there was a 14% decrease in risk for all coronary events, and a 27% decrease in risk of death from cardiovascular disease.

“Fiber trumps everything,” he says.

Choose this type of diet over high-protein

Because fiber is critical to gut health, Spector encourages eating at least 30 different plants per week, especially fermented foods and plants that come in a rainbow of colors.

By focusing on quality, plant-based foods—over calories and protein—he adds, you’ll likely be eliminating the worst ultra-processed foods from your diet in the process. Dr. Megan Rossi, author of How To Eat More Plants and Love your Gut, and a practicing dietitian and nutritionist, wrote in her book that the gut microbiome needs to receive “an abundant and diverse range of fiber.” That balance of bacteria in the gut can help regulate blood sugar, support digestion, and strengthen the immune system. 

Fiber has also been associated with reducing the risk of heart disease, obesity, and cancer. The U.S. Dietary Guidelines recommend that women eat 22 to 28 grams of fiber per day, while men should aim for 28 to 34 grams of fiber per day—but on average, Americans eat about to 10 to 15 grams of fiber per day, according to Harvard Medical School.

Eating 30 different plants can sound difficult, but Spector says it doesn’t have to be.

Plants you wouldn’t think of  like nuts, seeds, herbs, spices, and grains like quinoa, amaranth, and buckwheat, count towards that total. Spector starts his day with 12 different plants by eating fruit and a blend of nuts and seeds.

You can even count a purple carrot and an orange carrot, or a red pepper and a green pepper, as two different plants, he says, because they have different chemical compositions and nutrients. Canned and frozen fruits and vegetables, count, too..

But eating a plant- and fiber-forward diet doesn’t mean you have to eliminate meat. Just make sure plants take up at least 50% of your plate.

“There’s nothing wrong with meat, as long as it only takes up a small portion of your plate,” Spector says.

You can also get quality protein from plants, like beans and legumes, adds Spector.

“We’ve got to start thinking differently about feeding ourselves,” he says.