Metabolism 101

The boom-and-bust energy of a Standard American Diet (SAD)

VIV Research
·
September 20, 2021

Have you ever eaten a decent-sized meal and then felt hungry soon after? How could that happen? It certainly seemed like you were eating enough to feel satisfied and energetic for the next several hours.

The likely answer: It’s what, not how much you ate that’s to blame.

Let’s say your meal was a typical offering from a fast-food restaurant. Its main constituents of processed carbohydrates and unhealthy fats are hallmarks of the standard American diet (which we like to call “SAD,” but, as far as your body is concerned, these are definitely not happy meals).

When your body starts to process this high-sugar/high-fat meal, your digestive system releases a hormone known as glucose-dependent insulinotropic polypeptide, or GIP. As GIP goes to your brain, your normal metabolism of leptin, a hormone associated with feeling satiated, is affected. Specifically, the release of leptin into your bloodstream is dramatically curtailed. One important consequence of both GIP release and leptin production gone haywire is that your body braces for a rush of carbohydrates, and prepares to deal with a sudden rise in your blood glucose (what you might call “blood sugar”) by loading insulin.

The graphs below illustrate this harmful process. In these graphs, the blue/red line represents your blood glucose (BG); the line is blue when BG levels are within your body’s preferred range, and red when they’re not. The white bar represents the amount of time after your SAD meal.

Food digestion starts in the mouth, as saliva starts the breakdown of carbohydrates. After stomach acids break down food further, it enters your small intestine, where absorption and additional digestion take place. As you can see from the white bar, at this point your BG levels post-meal haven’t been affected much.
As the carbohydrates enter the blood, your BG level rises causing a spike. The size/height of the spike varies, depending on the amount and type of carbs consumed and the absorption rate of the body at that time. In our hypothetical example, the meal causes a huge spike, and BG levels have more or less doubled compared to when you sat down to eat.
The spike in BG triggers the body’s counter-response: Insulin releases from the pancreas, where reserves of pro-insulin are ready and waiting. The amount of insulin released is proportional to the amount and type of carbs absorbed. In the case of your not-so-happy SAD meal, the amount and type of carbs and fats absorbed cause a large amount of insulin to be released.
The release of insulin leads to BG level lowering. As you can see in the white bar, in this instance your BG level falls even faster than it rose. Within two(or more) hours or so your BG level will have spiked dramatically, returned to its pre-meal level, and even dipped below that baseline. This crash of your BG level spurs your body to start to raise your BG again through, amongst a cascade of neurological/endocrine responses, the release of the hormone adrenaline, which also hastens your heart beat and otherwise stimulates your body’s fight-or-flight response.

In this post-crash zone, with your BG level lower than it was just a few hours ago despite your high-calorie meal, and adrenaline coursing through your bloodstream, a hunger trigger creates the desire to eat again—and the cycle continues.

There are also long-term effects from SAD meals to consider. Any one meal might not cause a particularly severe boom and bust of your BG levels. But over time, the constant swings can take a toll, and can lead to increased fat storage and the development of chronic conditions such as type 2 diabetes.

Put another way, conventional nutrition tends to look at the contents of your daily diet mostly through the lens of whether you’re getting adequate vitamins and minerals. There’s not as much attention given to how regular insults to your body’s energy-management system can wreak havoc on that system and, eventually, your health.

What’s a better approach? The graph below illustrates what happens to BG levels in the two hours after a breakfast of ricotta cheese and raspberries.