This week’s blog is about the plant-based diet. Diet is by far the most important driver of health. & yet the scientific evidence is confusing. So the debates about diet are endless.

The balance of macronutrients (low fat vs. low carb) might be the most extensive debate. There are two camps in health circles: low carbers vs. low-fat dieters. There may be one thing that drives more passionate debate than the balance of macronutrients; it’s the source. Are you plant-based or even vegan? Or are you low-carb or even keto (or even carnivore?)

I have a slightly different concern, based on a couple of simple but important facts. First, more than half of us cannot metabolism one of those three macronutrients (carbs)without damaging our bodies. And second, over 90% of us with that problem have no clue that it’s happening. I simply think we should assess our situation before selecting a diet. 

For over three decades, I ate a plant-based diet. Then I developed the metabolic problem (prediabetes). Then I switched from plant-based to low carb. That statement is not uncommon, given common perceptions about healthy diets over the past decade. But in reality, that statement can be confusing. Why? Because you can be both plant-based & low-carb. You can even be vegan & low-carb. There are reasons that people tend to equate plant-based with low-fat dieats just like there are reasons that people tend to equate low-carb diets with meat-based diets. 

The rest of this article will demonstrate more of the confusion about plant-based, low-carb, & other dietary diets. There are solutions to this confusion. We’ll cover those later. 

The stimulus for creating this video came from watching the movie “What the Health?” It made me think, but not in the way the writer intended. 

Over the years, I developed insulin resistance. As I stated, I came from 30 years of a plant-based diet. And I’ve done this for a living most of my career; I ran the Preventive Medicine program at Johns Hopkins over 30 years ago. When I developed insulin resistance, it shifted my health priorities completely. I had to include carbohydrates and starches into my list of concerns. Previously, it had simply been mostly calories (the “bank account” theory of weight management.) Now, it wasn’t just about keeping my weight down; it was also about managing my blood sugar on a daily basis. 

Carbs give 4 calories per gram, & fats are 9 calories per gram. So, to maintain the same calories on a low-carb diet, I needed to eat less than half the grams of food I’d eaten on a low-fat diet. Why not just keeping eating low-fat & high-carbs? It was simple. High-carb meals were now spiking my blood sugar to dangerous levels. 

That created a challenge for me. But it was actually a far bigger public health problem. Why? More than 90% of people with the same problem (prediabetes) don’t know they have it. The CDC has said that 1/3 of US adults have this, & more than 90% don’t know it. More recent data from the UCLA & JAMA network indicate it’s over half. And that’s using screening methods that miss a lot of prediabetes (fasting glucose & A1c). If you use a better screen (like a GTT or Kraft Insulin Survey), there are far more prediabetics than even the 50%. 

Since this problem is so common, blood sugar has to become a priority. And blood sugar cannot be a priority while ignoring carbs (or body fat). Let’s examine some of the confusion.

Sugars vs Complex Carbs

“What the Health?” drew complaints from many places in the low-carb community. Critics tended to focus on sugars, “Look, they’re not saying anything about sugar. They’re saying sugar is okay.” Yes, that’s a problem. Sugar brings risk, whether you’re insulin resistant or not. But most people think “complex carbs” or “whole grains” are safe. Glycemic values prove otherwise. 

Other Mistakes: Fiber vs. Other Carbs

Another critical problem involves fiber. Fiber consists of carbs, yet it has little to no glycemic impact (ability to raise blood sugar). If you look up carbohydrates, vegetables, or plant-based carbohydrates, you see asparagus and legumes. Many legumes have a significant glycemic load, but others don’t. The following have a substantial impact on blood glucose: potatoes, figs, bananas, apples, grapes, mangos, etc.

What is the difference? Fruits have more simple sugars; vegetables are full of more complex carbohydrates. If you’re insulin resistant, it doesn’t matter a whole lot, sugar is sugar, and your body can quickly break down the complex carbohydrates.



Food Content & Food Content

Let’s talk about food content. 1.5 cups of grapes have 24 grams of sugar. Grapes are fruit, so they’re healthy, right? No, not if you have diabetes. They’re like orange juice, lot of sugar. And that sugar’s in a liquid form, so it hits the blood sugar immediately. 

Here’s another surprise we found with asparagus. Asparagus is not a big deal from a carbs perspective. Not many calories, ten calories for a quarter cup. Total carbs, 2 grams. So why is asparagus a problem? 

The key is glycemic carbs. Grape juice raises your blood sugar. Asparagus doesn’t. But again, glycemic impact is too difficult for many folks. They don’t want to worry about it. 



I had an excellent prevention-oriented, public speaker friend who’s a dietician. He said, “I don’t get what you’re talking about with the carbs. Are you talking about net carbs”?

 I won’t get into that today, but there is some component around net carbs. If you look at vegetables like broccoli and asparagus, they have carbs, but they don’t have that many. You don’t have to worry about the carbs. You do have to worry about carbs with grapes, apples, and other fruits. 

Other fruits are not that bad for people with diabetes; Blueberries are a good example; they have a lower carb count; however, “not so bad” is a relative term—1/4 cup of blueberries =20 calories. That might not be bad, but it’s still 5 grams of carbohydrates. And these carbohydrates are in juicy, pulpy fruit. The sugar goes straight into your bloodstream.




The low-carbers usually are big fans of avocados. Many of us like avocado, & especially guacamole, but it’s hard to keep it fresh as I got into plant-based foods.

There’s a company called Wholly Guacamole that’s found a way to keep it fresh for a long time by packaging. If you want to call that “processed food”, be my guest! You still have 5 grams and 100 grams of calories. That starts to get into that glycemic index. Avocados – I don’t think anybody will argue with you that avocados are glycemic or high-carb food.  

Calorie Source, Calorie Type, & Health

The bottom line is this: you can get a lot of sugars & other carbs in plant-based food, just like you get a lot of fats and oils in animal-based nutrition. There’s some evidence that sugars make you fat. There’s also evidence that eating fats make you fat. The reality is, I think there’s some case either way. I’m not going to argue that point; I’m going to say that being obese is a significant risk factor for insulin resistance, & therefore dying.

Both diabetes & prediabetes are significant risk factors for heart disease, cancer, stroke, and even Alzheimer’s and the disabilities associated with these conditions.

What do you think? Is a plant-based diet the solution for prediabetes? Or low-fat? Or is it just too complicated? 

I wish it were easier. But it’s not. & it’s our health. So, yes, it’s important.




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