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Will Low-Carb Diets Cause Blood Sugar Levels to Drop?

author image Andrea Cespedes
Andrea Cespedes is a professionally trained chef who has focused studies in nutrition. With more than 20 years of experience in the fitness industry, she coaches cycling and running and teaches Pilates and yoga. She is an American Council on Exercise-certified personal trainer, RYT-200 and has degrees from Princeton and Columbia University.
Will Low-Carb Diets Cause Blood Sugar Levels to Drop?
Bread, as a major source of carbs, spikes your blood sugar. Photo Credit: monticelllo/iStock/Getty Images

A high-carb diet causes your body to live in a state of constant high-blood sugar levels and spiked insulin loads. When you cut back on carbs, you lower blood sugar and insulin levels to reduce inflammation and improve your body's ability to burn fat.

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If you're accustomed to eating a very high-carb diet and suddenly switch to a very low-carb diet, you could experience rather dramatic drops in your blood sugar during the first few days or weeks of your transition. This low blood sugar can cause notably uncomfortable side effects and intense cravings.

Carbs and Blood Sugar

Your body converts consumed carbohydrates into glucose, a type of sugar. When the glucose enters your bloodstream, it leads to an increase in your blood sugar level.

The pancreas produces insulin in response to spikes in blood sugar, which helps your body store the sugar for energy. This insulin release subsides when your cells absorb the sugar and your levels stabilize. In a healthy body, the surge of blood sugar and insulin is relatively moderate and keeps you evenly motoring through your day.

When you eat lots of carbohydrates, your body's blood sugar remains consistently high and your system constantly pumps out insulin. This chronic elevation of blood sugar and release of insulin causes inflammation, an increase in fat storage and an inability to burn stored fat.

Chronically high blood sugar levels increase your risk of disease, including heart disease and type 2 diabetes. You crave carbohydrates regularly for energy, because your body isn't efficient at using stored fat for fuel.

How a Low-Carb Diet Impacts Blood Sugar

If you regularly consume a large amount of carbohydrates, especially refined ones like white bread and soda, you may experience a notable drop in blood sugar when you drastically reduce your carb intake. In the first week of carb reduction, your body will seek to maintain your high sugar intake. You'll crave carbohydrates and may even feel weak because your body hasn't yet become efficient at burning fat for fuel.

Over the course of several days, and sometimes weeks, your system adjusts to more stable blood sugar levels and utilizes more stored fat for fuel. These are some of the primary benefits of a low-carb eating plan, but the adjustment period can be difficult.

Side Effects of Low Blood Sugar

You might need as long as three weeks to adjust to low-carb eating. For the first day or two of the plan, your body runs on stored glucose in your liver and muscles -- and your insulin levels may remain elevated. But, when you burn through these stores, your body still produces the same high levels of insulin it has been trained to produce, even though your carb intake is down.

When you produce more insulin than necessary, blood sugar levels plummet. Your body struggles to normalize them, producing adrenalin in an attempt to jolt the liver into breaking down stored energy. Your nervous system releases the neurotransmitter acetylcholine that prompts sweating. These two compounds can also lead you to experience severe side effects.

While many may feel just a general malaise and crave carbs, others can have a full-on hypoglycemic attack. This includes heart palpitations, dizziness, irritability, shakiness, nausea, flushing, headaches and even a panic attack.

The seriousness of your symptoms often depends on how drastically you reduce your carb intake. If you reduce your carb intake only moderately -- to 100 to 150 grams for example -- you may not experience such severe symptoms. Reducing carbs to 20 to 50 grams per day, however, can have a big impact.

How to Minimize Drops in Blood Sugar

Easing into a low-carb diet may help you avoid serious drops in blood sugar. Instead of going from a standard 225 to 325 grams of carbs per day to 20 grams, decrease your intake by 20 to 30 grams daily for several days until you reach your target intake.

Also, eat small meals every three to four hours to help stabilize blood sugar levels.

If you do experience intolerable low-blood sugar symptoms, such as a panic attack or extreme shakiness, you might need to drink a small glass of orange juice or have another small, high-carb snack to provide relief. Count this as part of your day's carb intake and, over time, your need for such palliative cures should diminish.

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