If food is medicine, many Americans are in dire need of a new prescription, according to experts.

Adults who stick to a healthy diet are much less likely to experience obesity, heart disease, diabetes and even some types of cancer, says the Centers for Disease Control and Prevention (CDC) — yet most Americans aren’t getting the nutrition they need.

Worse still, they’re eating excessive amounts of the wrong things.

“Nutrition is thought to dictate about 80% of one’s health, and obesity irrefutably shaves nearly 10 years off a person’s life,” said Dr. Brett Osborn, a board-certified neurosurgeon in West Palm Beach, Florida.

“You can extend your ‘health span’ — or the time that you remain fully functional and free of disease — by simply following some basic nutritional principles,” he said.

Osborn, who is also the founder of a preventative health care and anti-aging facility, Senolytix, shared with Fox News Digital the 10 most critical nutrition mistakes people are making — and what they should be doing instead.

Osborn described excess sugar consumption as “the root of all evil.”

“Sugar, by definition, is a high glycemic index carbohydrate, meaning that once it enters the gut, it immediately crosses the bowel lining and enters the bloodstream, causing a rapid rise in blood sugar,” he said.

“In response, the pancreas secretes insulin, and the sugar (i.e., glucose) is shuttled into the cells for use as energy.”

But there’s a problem, Osborn said: The sugar molecules are released into the bloodstream so quickly that they damage the arterial walls — which causes inflammation.

“The next thing you know, there is a large plaque within a major artery of the heart, and you’re one step closer to your first heart attack,” he warned.

“To add insult to injury, eating simple carbohydrates shuts off fat burning by spiking insulin levels, and at the same time turns on fat production,” he said.

Osborn recommended limiting simple carbs like bread, pasta, rice, candy or other things that taste sweet.

“To add insult to injury, eating simple carbohydrates shuts off fat burning by spiking insulin levels, and at the same time turns on fat production,” he said.

“They train your body to burn sugar, and all excess is stored as fat,” he said. “This further stokes inflammation and places you on the accelerated train of aging.”

The experts at Osborn’s Florida clinic recommend consuming only carbohydrates with a glycemic index of 40 or less.

The glycemic index (GI) is a rating system for carbohydrates that indicates how quickly they cause a spike in blood sugar (glucose).

“Low-GI foods will keep you in a fat-burning state indefinitely by maintaining low insulin levels, a barometer of health,” Osborn said.

Some high-GI foods include bread, candy and cookies, while low-GI foods include fruits, unrefined grains and non-starchy veggies, according to Verywell Health.

Eating portions that are too large can lead to overeating and daily caloric surplus, according to Osborn.

“Everything in the US is ‘super-sized,’ including foods that are potentially healthy,” he said.