Q: Are all calories created equally?

A: Not when they’re paired with foods that change how your body absorbs the calories.

I’ve just finished listening to Dr. Peter Attia’s 2018 interview with Dr. Robert Lustig, who is a researcher, an expert in fructose metabolism, and a former pediatric endocrinologist.

One of the major takeaways from their discussion is the importance of “context” when it comes to your diet; specifically, the impact that sugar can have on your body, and the way that eating other foods in conjunction with sugar changes the way that your body reacts.

Essentially, here’s what I hope you’ll find useful to know (and what I want to remember):

  1. Glucose is used by virtually all forms of life. It’s the default fuel for human brains and is a vital part of a normal, healthy diet.

  2. Fructose is not naturally a large component of human diets, and excess fructose in the body can lead to liver dysfunction.

  3. Sugar (a.k.a. sucrose) is made up of… GLUCOSE + FRUCTOSE. So sugar (in all its forms) gives us nutritional value (glucose) as well as a potentially harmful substance (fructose).

    To be clear, fructose is not inherently bad. But high levels of fructose will lead to metabolic dysfunction, such as diabetes, and/or death (secondary to cancer, for example).

    Now, here’s where we get to my point about all calories not being created equall

  4. It turns out, other foods can affect how your body absorbs sugar by physically impeding or delaying its uptake.

    Take fiber, for example. When you have adequate levels of soluble and insoluble fiber in your digestive tract, they come together to form a physical barrier that slows down your body’s absorption of sugar. Imagine a mesh strainer, covered with a layer of petroleum jelly. Like the mesh and the petroleum jelly, he insoluble fiber (e.g., the stringy bits of celery), plus the soluble fiber (e.g., the pectin in gelatin) combine to form a hydrophobic barrier. This is basically what happens in your gut when you have adequate amounts of both types of fiber. (Note that the barrier will not form if either soluble or insoluble fiber is missing.)

    This barrier allows your body to process small amounts of sugar at a time, thus avoiding the insulin resistance which comes from being biochemically overwhelmed with sugar processing.

  5. This is also why eating a whole apple is better for you than drinking apple juice; the soluble and insoluble fibers from the fruit slow down the absorption of sugar in the gut. Instead of the fructose being absorbed quickly once it hits the duodenum, the fiber barrier keeps most of it from being absorbed and allows the sugars to make it to the jejunum, where your body will absorb some of it, and much of it will be used as fuel by your gut bacteria, many of which thrive on fructose. This saves the liver from quite a lot of damage over time.

  6. At this point in the discussion, Dr. Lustig pointed out that if you don’t have enough fiber, and most of the sugar you eat is absorbed in the duodenum, the gut bacteria in the jejunum will then start eating the lining of your intestine to make up for the lack of food. Dr. Lustig speculates that this might be the source of colitis, leaky guy syndrome, and even Crohn’s disease.

  7. Most importantly, Dr. Lustig points out that you can’t outrun a bad diet. That is, no amount of exercise or training can make up for a body that’s being biochemically assaulted by the food that it’s taking in.

So, there you have it: my imprecise notes from Peter Attia’s interview with Dr. Lustig. There are a lot more details and nuances to keep track of, but these are the main points.

Dean Balan