Energy Lows: What Causes Them and How to Avoid Them

By Laura High  @healthwriter61
May 19, 2016

You know the drill — it’s the middle of the day and you’re sitting at your desk nodding off. Here’s how to keep them at bay.

There was a time when it wasn’t unusual for me to feel so tired during the workday that I literally wanted to crawl under my desk and fall asleep. I’d have given almost anything to be able to take a 10-minute power nap. These episodes didn’t necessarily come in the afternoon — sometimes I’d start doing the head bob mid-morning, and occasionally my eyelids would turn to lead when I was actually driving to work. 

Many people can relate to feeling extreme fatigue at various times during the day. The episode may be relatively short — 10 to 20 minutes — or it may last an hour or longer. No matter how long it lasts, it can be an excruciating (and embarrassing) experience. So what causes these energy dips, and what can you do to avoid them? 


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It’s all about your blood sugar

Most often energy lows are the result of low blood sugar (hypoglycemia). Just like a car needs gas to run, your brain and body need fuel in the form of food for peak performance. We’ve all heard that breakfast is the most important meal of the day. This is true for a variety of reasons, but if you’re feeling tired before noon and you didn’t eat breakfast, that’s likely the reason.

Many people who do eat breakfast also experience mid-morning lows. If that’s the case for you, take a closer look at what you’re eating. It’s no secret that a cup of coffee and a doughnut doesn’t cut it as a good morning meal, but what should you eat? Avoid the doughnuts, of course, but the classic bowl of cereal, slice of toast, and glass of juice isn’t much better. 

The most common breakfast cereals are usually highly processed and full of sugar. Toast may not be so bad if it’s made from whole grains, but if it’s toasted white bread — especially if you spread it with butter and jelly — it’ll push your blood sugar even higher, setting you up for a bigger dip later. Most juice contains a lot of added sugar. But even if it’s fresh squeezed, juice requires very little digestion, and its sugars hit your bloodstream almost immediately.

Some words about carbohydrates

For most of us, the culprit causing a mid-morning or post-lunch crash is eating too much of the wrong kind of carbohydrates. Carbohydrates, protein, and fats are the three macronutrients in the human diet. Carbohydrates typically are the majority of what we eat. 

When you eat carbohydrates, your body breaks down the digestible part into various sugars to be used as fuel. The amount of carbohydrates recommended for adults is 130 grams per day. Additionally, carbohydrates should represent between 45 and 65 percent of your total daily calories (energy).

But the term carbohydrate can be a confusing catch-all of many types of food. The 2015-2020 Dietary Guidelines for Americans breaks carbohydrates into three sub-categories: fiber, starches, and sugars, which encompasses many foods and food ingredients.

Carbohydrates are also often characterized as either “simple” or “complex.” Simple carbohydrates are sugars (for example, fructose and glucose) with simple chemical structures your body can quickly turn into fuel, leading to a rapid rise in blood sugar. Some examples of simple carbs are table sugar, brown sugar, corn syrup, honey, candy, soft drinks, fruit drinks, jams, and jellies.

As the name implies, complex carbohydrates have a more complex chemical structure and so take longer to digest leading to a slower rise in blood sugar. Complex carbs are commonly found in whole plant foods, including:

  • Fruit
  • Green vegetables
  • Whole grains and foods, such as barley, brown rice, oatmeal, pasta, and whole-grain baked goods,
  • Beans, lentils, peas
  • Starchy vegetables such as potatoes, sweet potatoes, and winter squash

Technically, complex carbohydrates are any kind of starch, which would include white bread, cookies, pastries, and cakes, and a variety of other foods considered unhealthy. To help ensure you’re eating good carbs, stay away from processed foods as much as possible, and make sure any you do eat are made from whole grains.


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Glycemic index and glycemic load

A tool you can use to evaluate your carb quality is the glycemic index (GI). GI ranks carbohydrates on a scale of 0 to 100, according to how much they raise blood sugar levels when eaten. A “low-GI” food has a ranking of 55 or lower. Medium GI foods are ranked at 56 to 69. High-GI foods are ranked at 70 to 100. Just like simple carbs, high-GI foods are rapidly digested and absorbed and cause significant spikes in blood sugar. A diet too rich in high-GI foods can put you at risk for type-2 diabetes, cardiovascular disease, and being overweight. Like complex carbs, low-GI foods are digested and absorbed more slowly and result in a more gradual rise in blood sugar.

A food’s GI ranking is determined when it is consumed by itself on an empty stomach. That’s not how most of us eat. Usually, you eat a baked potato (with a GI of 85) as part of a meal that may include a grilled chicken breast and a salad with vinaigrette dressing, for example. The protein, fiber, and fat in those other foods lower the GI of the potato. 

Additionally, GI doesn’t account for the actual amount of a food we’re eating. According to the Academy of Nutrition and Dietetics, a food’s GI ranking is calculated based on a serving that contains 50 grams of carbohydrate minus the fiber. That would be reasonable for a serving of white rice (GI ranking of 64), which contains 53 grams of carbs per cup. But beets, which also have a GI ranking of 64, only contain 13 grams of fiber per cup. So you’d have to eat about 4 cups of beets to get 50 grams of fiber, and that’s not a likely serving.

Another way to evaluate the quality of a carbohydrate is its glycemic load (GL). The formula used to determine GL corrects for the shortcomings of the GI system by combining portion size and GI into a single number. A GL ranking of more than 20 is considered high, between 11 and 19 is moderate, and 10 or less is considered low. Applying the formula, that cup of beets now has a GL of 8.3.

The international GI database is a searchable database that ranks thousands of foods based on their GI and GL. 

Another benefit of eating good carbs is fiber. Fiber can slow digestion and therefore slow the rate at which your blood sugar rises. Fiber also keeps you feeling full longer. The total grams of fiber recommended per day is between 30 and 38 for men, and between 21 and 26 for women. 

Other factors

In addition to fiber, adding protein and healthy fat to a meal can also slow digestion and help maintain steady blood sugar levels, but be careful. You digest protein more slowly, and that’s one reason it helps keep your blood sugars level longer. But if you eat too much protein, your body has to work really hard to digest it, which takes a lot of energy and can also leave you feeling tired.

Be mindful of how much caffeine you’re consuming, especially if you drink coffee doctored with milk and sugar. Although caffeine can give you a boost, it too can result in a crash later. Coffee is also a diuretic. Make sure you’re drinking enough water, whether you’re drinking coffee or not. Dehydration has been shown to cause a whole host of symptoms, including fatigue.

Extreme fatigue during the day can be a symptom of sleep apnea. Sleep apnea is a breathing problem. Your brain may fail to send correct signals to the breathing muscles (also called central sleep apnea), or, more often, the airway collapses or is blocked because of fat or abnormalities in the throat and nasal passages (known as obstructive sleep apnea). When your breathing pauses or becomes shallow, you’re pushed out of deep sleep. Although patients don’t actually wake up, they end up sleep-deprived and become more vulnerable to depression, diabetes, stroke, high blood pressure, heart failure, and car accidents from sleepiness at the wheel. 

Everyone is different, and you may have to experiment a little before you come up with food combinations that work best for you. If cereal, toast, and juice are part of your morning routine and you’re struggling with low energy before it’s time for lunch, try swapping out the corn flakes with oatmeal, replace the toast with a piece of ham or other lean protein, and have a fiber-rich apple or other fresh fruit instead of juice. 


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April 10, 2020

Reviewed By:  

Janet O’Dell, RN