“Fighting sleep has become a national pastime,” the headline roars in a late 2013 story by syndicated columnist Mitch Albom. But this story is not a product placement for 5-Hour Energy or SuperBeets or even, for the older newspaper-reading demographic, NoDoz. It is about why many people feel sleepy or drowsy a few hours after eating a meal. Let me be clear: I do not, ever, feel sleepy after a meal anymore (except on Thanksgiving).
The reason why people feel sleepy a few hours after eating a typical meal is physiologic. It is very real. I know because I experienced it frequently myself for most of my life. And it is related to energy, particularly available energy. The body manages homeostasis by summoning energy from available sources. That’s why we eat – to replenish our level of available energy by mouth. Our body also stores energy, as body fat, for this purpose; however, this stored energy is not always available for use.
Of the three macronutrients, protein, carbohydrates and fat, protein is the only one that is not an energy source that can be used directly as a fuel when needed. Protein breaks down to amino acids to be taken up by muscle, for repair, and many other cellular and hormonal uses in the body. Leftover amino acids, if any, are stored in the liver.
Carbohydrates, both simple sugars and complex carbs, digest quickly to make energy. Digestion occurs in just minutes for highly processed carbs found in most food products in today’s marketplace, especially liquid and refined forms. All carbs ultimately enter the bloodstream as the single-molecule glucose, raising the level of “sugar” in the blood. The average body needs just under one teaspoon of sugar in our blood. A meal with 100 carbs is equivalent to 13 teaspoons of sugar, so our blood sugar “spikes.” This “quick energy” doesn’t last. A few hours after eating a meal loaded with carbohydrates, most of the glucose is taken up and the blood sugar level “crashes.”
When high levels of glucose are detected in the blood, the body secretes insulin to take it to where it is needed, to the muscles for example. That’s what exercisers call “carb loading.” After replenishing the cells, the balance of circulating glucose goes to the liver to be stored as glycogen. And when the liver gets overloaded with glycogen, especially when it is deluged with a load of liquid sugar (as in soft drinks and fruit juice), it converts the excess to fat by a process called lipogenesis. That’s right; the sugar overload in your soft/juice drink converts to body fat.
The body does this to protect itself from sugar because table sugar and most of the sugar in fruit is half fructose. Fructose is toxic when it is over consumed. That’s why fructose is diverted and goes via the portal vein straight to the liver. One of the liver’s functions is to detoxify things. The liver then converts the fructose to glucose and then to glycogen to be stored in the liver. But, if the liver’s glycogen stores are full, it converts it to fat. And some of this fat is stored inside the liver, creating Non-Alcoholic Fatty Liver Disease (NAFLD). NAFLD is near-epidemic today.
Fat, the other energy source among the 3 macros, is also the densest. It has 9 calories per gram versus 4 for carbs. This makes it ideal for “long term” storage. The body is designed to put it away in storage and to make it available when needed. So, where does the body go for energy 1-2 hours after a high-carb meal? In a body with a disregulated glucose metabolism, as in a Pre-diabetic or Type 2, Insulin Resistance results in the level of circulating insulin staying high while the pancreas pumps out more to help glucose be taken up at the cellular level. As a result, the energy in stored body fat it not available for use, and we feel sleepy or drowsy a few hours after a meal.
So, do we have a reliable energy back-up system? You bet we do, but to burn body fat for energy – to maintain a level blood glucose and stable “wake” state – we need to get our blood insulin level low enough to access our fat cells. The only way to lower blood insulin levels in the Insulin Resistant is to eat way fewer carbohydrates.
When I am in this ketogenic state, my body burns fat as its primary energy source. As a consequence, my blood sugars are relatively stable all day long. My blood sugar doesn’t spike after a meal and then crash a few hours later. I do not feel sleepy or drowsy between meals. I don’t need 5-hour Energy or a sugar beet snack for a “pick-me-up.”