There are different reasons that people follow low carb diets. In addition to weight loss, a primary reason is to manage blood sugar (blood glucose) levels. Many of us follow a low-carb eating plan to keep our blood sugar normal and stable.
To fully understand the connection between carb consumption and blood glucose, it’s helpful to familiarize yourself with how the body processes blood sugar in a normal state and how the process changes if someone has diabetes.
How Carbs Impact Blood Sugar
Carbohydrates have a direct impact on blood glucose. All foods with carbohydrate—whether juice drinks, jelly beans, or watermelon—break down into simple sugars in the body. Even foods that we don’t consider “sugary” break down into simple sugars. The carbohydrate in most starchy foods (like potatoes and bread) is simply a collection of long chains of glucose, which break down into sugar in the body.
These simple sugars turn into glucose through metabolic processes. As a result, our blood glucose levels begin to rise. When this begins to happen, beta cells in the pancreas sense the increase and release insulin.
Carbohydrates are converted into simple sugars in the body. Even carbs that aren’t sweet—such as starchy foods— are converted into sugar and raise blood glucose levels.
Normal Insulin Function
In a healthy body, when blood glucose levels go up, the body responds by secreting the hormone insulin. Insulin helps to stabilize blood sugar by removing it from the bloodstream and facilitating its storage. Insulin can also help the body to use blood glucose for immediate energy. Simply put, insulin acts as a catalyst to use glucose or move it into body tissues so that it can be used at a later time.
If the glucose (sugar) is not used immediately, there are two primary storage sites: Glucose may be stored as glycogen in the skeletal muscles or in the liver. The excess sugar may also be converted into fatty acids, circulated to other parts of the body and stored as fat.
As glucose in the bloodstream is cleared away (either for immediate use or for storage), blood sugar levels return to normal. Beta cells sense this change and stop releasing insulin.
Insulin is a hormone that is secreted in response to high blood glucose levels. It allows your body to use or store the blood sugar so that glucose levels return to normal.
Insulin Resistance and Diabetes
People with insulin resistance or diabetes are unable to balance blood sugar when the process of converting food—specifically carbohydrates—into energy takes place.
People with diabetes either don’t make insulin (type 1 diabetes) or have become resistant to insulin (type 2 diabetes) because too much of it has been circulating in the system. Those with type 1 diabetes inject insulin to manage blood sugar.
However, those with type 2 diabetes or insulin resistance often need to find other ways to manage blood sugar because their body’s cells are unable to use insulin properly. As a result, their blood sugar levels stay elevated.
As the body tries harder and harder to bring blood sugar down, more insulin is released which makes the cells less sensitive to it and more resistant. Over time, the pancreas is permanently damaged and other bodily functions are affected such as hardened blood vessels, among other ailments.
In addition, when insulin levels are high, weight gain is more likely since a main function of insulin is fat storage.
To avoid these health problems, keeping blood glucose within a normal range is important. Even people who do not have diabetes have an increased risk of heart disease with higher blood glucose levels.
One of the primary ways to manage blood sugar is to consume a low-carbohydrate diet—that is, avoid the foods that can cause blood sugar spikes in the first place.
People with insulin resistance or type 2 diabetes often use a low-carbohydrate diet to keep blood sugar levels stable and stay healthy.
Tips to Cut Carbs and Manage Blood Sugar
Low carbohydrate diets work for some people who need to manage their blood sugar, but they don’t work for everyone.
Some studies have shown that low-carb diets are an effective management strategy for obese patients with type-2 diabetes. Other studies have even shown that very low carbohydrate intake can help some patients reduce or eliminate the need for medication.
But additional studies have shown that some low-carb programs, such as the ketogenic diet, are hard to maintain because they are too restrictive. Furthermore, there is a lack of high-quality long-term research documenting the benefits of a low-carb diet for the management of blood sugar.
However, cutting out certain carbs is smart for anyone—regardless of medical status. Starchy carbs, empty calorie foods, and heavily processed products provide little nutritional value. If you replace these foods with more nutritious foods that provide fiber, protein, and healthy fats, you’re likely to gain a wide range of health benefits, including more stable blood sugar levels.
Low carbohydrate diets are effective in some people (but not all) for the management of blood sugar levels. However, almost anyone can benefit when they cut out less nutritious carbohydrates such as heavily processed products and empty calorie foods.
Personalize Your Carb Intake
There is no clear definition of what a low-carbohydrate diet is. For example, a ketogenic diet may restrict carbs to 10 percent or less of your total daily calorie intake, whereas other low-carb programs may allow 20 percent of your calories from carbs or more. The best number for you may take some experimentation.
It’s best to work with your healthcare provider and/or a registered dietitian to determine a level that is not only safe and effective but also realistic for you to follow for the long-term.
Fill up on Healthy Fats and Protein
At mealtime, fill your plate with foods that provide energy in the form of protein and fat. But try to choose the most nutritious sources.
For example, meat, poultry, and seafood that is grilled (not breaded or fried) are smart choices. Some dairy products like eggs and cheese may also work in your food plan.
When choosing fats, look for sources that provide mono- and polyunsaturated fats rather than saturated fats. Avocados, for example, are high in monounsaturated fat. Butter, on the other hand, provides less healthy saturated fat.
Choose High Fiber Foods
When choosing carbohydrate foods, look for foods with more fiber as it has a minimal effect on blood glucose levels. Fiber also provides other benefits: You are likely to feel full longer when you eat high-fiber foods, and consumption of high fiber foods can also help you to lower your LDL cholesterol.
High-fiber foods are generally plant-based foods that are closest to their whole form. For example, an apple provides fiber while apple juice provides none. Whole nuts provide protein and fiber (with some carbohydrate) but nut butters and nut milks often have sugars added during processing and may boost your carb intake.
Choose Sweeteners Wisely
Many people on low-carb diets use low-calorie or zero-calorie sweeteners. Products like Equal (aspartame) or Sweet’N Low (saccharin) add sweetness to coffee, tea, or other foods and beverages without impacting blood sugar.
However, there is some concern that these sweeteners may increase your cravings for sugary foods. Many products are much sweeter than sugar and can impact your ability to sense the sweetness of naturally sweet foods like fruit.
Additionally, some artificially sweetened foods use sugar alcohols to add flavor. Some sugar alcohols, like erythritol, have very little impact on blood sugar, while others, like maltitol, have a more substantial impact on blood sugar.
Some low carb eaters use the glycemic index as a tool when choosing foods to eat and foods to avoid. Although the glycemic index has its limitations as a tool, it can give a rough idea of how your body may respond to a given food which is important. However, it does not give an indication of the overall nutritional value of a given food.
Also, remember that serving size is also important. Eating a lot of a low-glycemic carbohydrate food will still raise your blood glucose. This is why many people find it’s easier just to limit foods with a lot of carbohydrates by following a low-carb diet.
High Fasting Blood Glucose on a Low Carb Diet
What happens if you follow a low-carb diet and your fasting blood glucose remains high? According to experts, in some cases, this is likely to happen. But it is not necessarily cause for concern.
If you follow a strict low-carb regime, you may experience a condition called “physiologic insulin resistance,” also called adaptive glucose sparing.
People who are on ketogenic diets or other very low carbohydrate programs train their bodies to use fat, rather than sugar, as fuel. If you do this effectively, your muscles start to reject sugar when it is available. That means more sugar stays in your bloodstream, even when you consume very little of it.
If this happens, work with your healthcare provider to adjust your testing regime. Testing for fasting insulin levels along with a fasting blood glucose test may provide more insight to help you manage your condition.