What is prediabetes?
The CDC estimates that 1 in 3 Americans have prediabetes, and up to 84% aren’t even aware they have it. Thankfully, although prediabetes is common, it is also reversible. Lifestyle changes and proper management can often slow or even stop prediabetes from progressing into type 2 diabetes mellitus.
Although the “pre” may make prediabetes sound like it’s not as serious as type 2 diabetes, prediabetes can still have significant and long-lasting health effects.
Prediabetes is on the list of type 2 diabetes risk factors and also increases the risk of developing other dangerous health conditions like heart disease and stroke. Even if it does not progress into type 2 diabetes, long-term damage to the blood vessels, heart, and kidneys may happen.
In people with prediabetes, blood glucose (sugar) levels are above normal. Those levels are determined by blood tests, such as the hemoglobin A1c test (which measures average blood sugar over the previous two to three months) or fasting blood sugar (checked after fasting for eight hours).
A normal A1c is under 5.7%, and diabetes type 2 is diagnosed at 6.5% or above, so an A1c of between 5.7% and 6.4% falls into the prediabetic category.
A fasting blood sugar should be under 100 mg/dl, so anything between 100 mg/dl to 125 mg/dl is considered prediabetic, with 126 mg/dl being one of the signs of type 2 diabetes.
Diagnosis of prediabetes is frequently made without symptoms, as long as the blood test results are the warning ranges above.
Part of the reason that a prediabetes diagnosis does not rely on a specific list of symptoms is that, unfortunately, there are no clear symptoms. That lack of symptoms is likely why the condition often goes overlooked and undiagnosed until it has progressed into type 2 diabetes. It is also why routine bloodwork is crucial for catching the problem early.
That said, a small percentage of people with prediabetes do develop a condition known as acanthosis nigricans. This skin condition commonly occurs in skin folds, including the under-arm area, the back of the neck, and the groin, and is tied to insulin resistance. The same areas may also develop small skin tags (skin growths).
While there are no symptoms that are really signs of prediabetes, signs and symptoms of type 2 diabetes are clearer, and will appear as prediabetes progresses into diabetes mellitus type 2.
Symptoms of diabetes type 2 can include:
Increased thirst (polydipsia).
Increased urination (polyuria).
Increased hunger (polyphagia).
Blurry vision (although this symptom can start during the prediabetic period as well).
Prediabetes risk factors
Although anyone can develop prediabetes, there are certain risk factors that may make it more likely:
Having a BMI in the overweight (25.0 - 29.9) or obese (>30) range. 
Being over 45 years old.
Having a first-degree relative (parent or sibling) with diabetes.
Being from a higher-risk race or ethnicity group (African American, Hispanic, Latina, Asian, Native American, or Pacific Islander).
Living a sedentary lifestyle.
Having certain health conditions including high blood pressure (hypertension), high cholesterol (hyperlipidemia), obstructive sleep apnea, and polycystic ovarian syndrome (PCOS).
Having a history of heart disease or stroke.
Having a previous diagnosis of gestational diabetes in pregnancy or having had delivered a baby weighing over 9 pounds.
Being a current or former tobacco smoker.
Having a larger amount of abdominal fat.
What causes prediabetes?
Prediabetes (just like adult onset diabetes type 2) involves the pancreas, which is why the disease is considered a disorder of the endocrine system.
The pancreas is an organ located next to the liver, and it performs various functions in the body. Beta cells located in the pancreas produce insulin, which is the key to the body’s ability to use blood sugar for energy.
When beta cells are working as usual and insulin is present in the body in normal amounts, glucose (blood sugar) can be efficiently used as energy.
When a person has prediabetes or type 2 diabetes, those beta cells aren’t working well. This leads to a decreased amount of insulin, resulting in less glucose being transported into the body’s cells. When that happens, much glucose stays circulating in the bloodstream, leading to high blood glucose levels.
Nutrition plays a crucial role in managing and even reversing prediabetes. By adjusting the diet and eating the right foods, blood sugar levels may be brought back down to the normal range, preventing the increase of prediabetes sugar levels into diabetes type 2 levels.
Proper nutrition for prediabetics can also help with weight loss and lower one’s BMI. As obesity is one of the type 2 diabetes risk factors, an improvement in diet can help prevent the onset of diabetes by both lowering average blood sugar and promoting weight loss.
Carbohydrates directly impact blood sugar, as they are broken down into the glucose the body needs for energy. While people with prediabetes usually need to reduce their carbohydrate intake overall, the body still requires some carbohydrates to be used for fuel.
There are two main categories of carbs — simple and complex — and the key is knowing which type to eat and which to avoid.
Simple carbohydrates are quickly processed by the body and often immediately add a large amount of glucose to the bloodstream. It’s these types of carbs that can cause a spike in blood sugar, which puts more demand on the body compared to carbs that steadily digest and release glucose into the bloodstream over a longer period of time.
While some simple carbs can be found in healthy food sources like milk (lactose) and fruit (fructose), many are found in processed foods. Simple carbs should generally be avoided, so those with prediabetes are urged to cut out foods and drinks that are high in simple carbs, including soda, fruit juice, white bread, and highly processed foods.
Complex carbohydrates are a better energy source for those with diabetes because they contain more usable benefits for the body, primarily because foods with complex carbohydrates also often contain vitamins, minerals, and fiber that help nourish the body. They are also more filling, and are typically digested by the body more slowly, which prevents the large blood glucose spike that comes from simple carbs. Whole grains, legumes (lentils, beans), and fresh vegetables are full of complex carbs and are better components of a prediabetes diet. Of course, carbs have calories so they should be consumed in moderation.
Prediabetic people should focus on consuming monounsaturated fats, which can lower the level of “bad” cholesterol in the body (“bad” is low-density lipoprotein cholesterol). Examples of foods rich in these healthier monounsaturated fats include avocados, olive oil, and certain nuts like almonds, cashews, and pecans.
Polyunsaturated fats are also considered healthy for many of the same reasons, as they contain omega-3 and omega-6 fatty acids. Walnuts, chia seeds, “oily” fish (like salmon and tuna), tofu, eggs, and peanut butter are all high in polyunsaturated fats.
It is essential to remember that these whole fatty foods may be healthier compared to their trans-fat counterparts such as fast food and fried foods, but they are also very high in calories, so they should be consumed in moderation and only as a small portion of the diet.
Prediabetes and exercise
Exercise is also a vital part of managing and reversing prediabetes.
Exercise can increase the body’s sensitivity to insulin. With higher insulin sensitivity, muscle cells are able to efficiently use energy during and after exercise. In addition, as muscles contract, the cells can use glucose even without insulin. The result is less circulating glucose in the bloodstream for up to 24 hours after exercise.
Health experts recommend 150 minutes of moderate exercise a week for adults, which works out to about 30 minutes a day, five days a week. This should be combined with strength training three times weekly.
People who are new to working out should check with a doctor before starting any new exercise plan and start slowly to reduce the risk of injury. Easy exercises to help introduce the body to regular exercise include walking, swimming, yoga, and biking.
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