The real culprit behind diabetes—printed in black and white

(Hint: It’s NOT fats)

Last month, I outlined common risk factors for heart disease—and what you can do about them. But, in 21st century America, you can’t really talk about heart disease without addressing the risk factors for type II diabetes as well.

Sadly, the most common type of heart disease today is cardiometabolic, caused by diabetes and metabolic syndrome.

So it’s not a big surprise that the guidelines from the American Diabetes Association (ADA) to prevent and manage type II diabetes and high blood sugar still spout the same nonsense about avoiding cholesterol and fats as the American Heart Association (AHA) guidelines.

Now, the ADA guidelines do have one measly mention about actually cutting back on sugar. But despite reams of compelling evidence that sugar and processed carbs are the problem when it comes to managing blood sugar, diabetes, and metabolic syndrome, the ADA has still insisted there’s somehow a “debate” about whether fat or sugar is the real culprit.

They may have finally settled their fictitious debate a few months ago. But before I get into the details, let’s first back up to understand how diabetes and other metabolic diseases became such pervasive medical problems…

How did the U.S. diet go so wrong for so long?

As an Insiders’ Cures reader, you know I look to history to help figure out how things went so wrong with our diet and health.

As a physician and anthropologist, I’ve studied many historical examples of populations that both subsisted on high-fat and high-carb diets. Generally speaking, populations residing in cold climates had higher meat and fat intake. And people residing in warmer climates could generally grow and consume more carbs in their diets.

Before the early 1900s, generations of carb consumers didn’t appear to develop metabolic diseases like they happen to do today. But during the 20th century, carbohydrates became highly processed (when manufactures also started adding artificial ingredients to expand their product’s shelf life for mass distribution, and other problems).

Lab experiments have found that some of these artificial ingredients cause increased insulin secretion and high blood sugar. In other words, they’re essentially endocrine, hormone, and metabolic disruptors that don’t belong in your body.

(Excess calories and excess iron can also cause increased insulin resistance—another reason to avoid iron supplements.)

Why processed foods are so bad for you

The processed foods that became so common in the last half century have dramatically changed the composition and quality of our food supply.

One study found that in 1938, Canadian diets consisted of 24 percent processed foods. By 2001, that number had jumped to 55 percent.1

Meanwhile, a 2016 study found that processed foods accounted for 58 percent of Americans’ caloric intake. And a whopping 90 percent of that “energy” was supplied by added sugar.2

All of these processed foods are increasing our intake of calories, carbohydrates, and fat—contributing to metabolic diseases like obesity and diabetes.

In fact, a 2019 study found that people who ate an ultra-processed diet consumed an average of 580 more calories each day than those who ate a diet of unprocessed foods—even though the diets were matched in terms of carbs, fat, fiber, protein, sodium, and sugar.3

Now, let’s take a closer look at the ADA debate on fats and carbs…

The skinny on fat, carbs, and metabolic health

At the ADA’s 80th Scientific Sessions in June, there was finally an enlightened, science-backed presentation—with real data—on the fat versus carbs issue.

Sarah Hallberg, DO, presented a convincing case supporting the metabolic health benefits of high saturated fat and total fat diets, compared with low-fat, high-carb diets.4

(The initials “DO” stand for doctor of osteopathic medicine. Osteopathic medical schools tend to include natural approaches like diet and nutrition in their curriculum, whereas regular [MD] medical schools do not. And Dr. Hallberg’s DO training certainly showed in her presentation).

According to Dr. Hallberg, studies show that eating more carbohydrates, while correspondingly decreasing saturated fat intake, increases the total amount of fats in the blood.

Meanwhile, eating more dietary fats actually decreases the level of fat in the blood. In other words, the amount of fat in the diet is not related to the amount of fat in the blood.

In fact, a higher level of saturated fat in the blood is actually a marker for excessive carbohydrate consumption, which can predict future metabolic disorders.

Plus, increasing the amount of fat in the blood at age 50 has been associated with increased C-reactive protein (CRP)— a marker of chronic inflammation—at age 70. And CRP is a key risk factor for heart disease and other chronic diseases, as I discussed in last month’s issue.

In addition, excess saturated fat in the blood is a marker for high triglycerides and abdominal fat—which are both major risk factors for metabolic disease.

Looking at the total diet

Other studies show that while a low-carb diet is higher in saturated fats, it actually results in decreased fats in the blood.

Here’s how it works: Lower consumption of dietary carbs results in reduced saturated fat synthesis, leading to decreased saturated fats in the blood and a better insulin response.

But higher carbohydrate consumption is associated with increased saturated fat synthesis and storage. That leads to insulin resistance—which can then lead to high blood sugar and type II diabetes. And this effect can take place quickly.

In fact, a study of obese men and women with type II diabetes found that just two weeks of a low-carb diet resulted in lower triglycerides, much-improved 24-hour blood sugar levels, better insulin response, and weight loss as a result of eating less.5 And, since this study was published in 2005, the results have been widely replicated in subsequent studies.

The bottom line is that low-carb, high-fat diets are beneficial for your heart, cardiometabolic health, and diabetes prevention. They result in healthy fat levels in your blood and do not lead to increased diabetes risk…giving you just one more reason to cut out sugar and not worry about cholesterol, as the science consistently recommends.

Eat clean, not lean

Looking at all of the historical, laboratory, and clinical evidence, it’s safe to conclude that humans do not require carbohydrates in our diets.

But, as I’ve often reported, the best way to eat is not to count every calorie, carb, or fat. The key is eating a balanced diet consistent of a variety of whole, natural foods, and avoiding unhealthy, processed foods.

Of course, sugar is the biggest single example of a natural plant product that becomes unhealthy when it’s highly processed. And now, “plant-based meats” are quickly challenging sugar for the dubious title of most toxic “foods.”

I’ve written before about how these fake meats combine cheap, processed plant matter with artificial ingredients, creating a frankenfood that masquerades as “healthy.” So, again, don’t be fooled by these ultra-processed fake meats. They aren’t better for you—or the planet—and are actually better off composted in your backyard than consumed in your diet!

If you want to truly lower your risk of diabetes and other metabolic diseases, all you need to know is this…

It’s not about eating “lean,” as in cutting fats, but eating “clean,” as in cutting out fake foods. So just say no to unhealthy, processed foods (remember, sugar and processed carbs are the leading culprits), and say yes to healthy, whole foods.

As always, you can’t go wrong with a Mediterranean-type diet, which is full of fresh, organic produce, grass-fed and -finished meat, wild-caught fish and seafood, organic, full-fat dairy, and alcohol (in moderation).


1“Processed and ultra-processed food products: consumption trends in Canada from 1938 to 2011.” Canadian journal of dietetic practice and research : a publication of Dietitians of Canada. 75. 15-21. 10.3148/75.1.2014.15.

2“Ultra-processed foods and added sugars in the US diet: evidence from a nationally representative cross-sectional study. “BMJ Open 2016;6:e009892.

3“Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake.” Cell Metab. 2019;30(1):67-77.e3.


5“Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes.” Ann Intern Med. 2005;142(6):403-411.