Prediabetes and Nutrition for Athletes: Optimizing Performance and Health

Author: Amelia Baker, RDN, CDCES, (Certified Diabetes Care and Education Specialist), CSSD

Co-Author: Briana Bruinooge, RDN, CSSD (Certified Specialist in Sports Dietetics)

prediabetes

Approximately 1 in 3 American adults have prediabetes, but what does this diagnosis mean? Is it important to address prediabetes as an athlete who has been diagnosed with prediabetes?

What is prediabetes?

Prediabetes is a condition where a person’s blood glucose values average higher than normal range, indicating impaired insulin sensitivity. It’s a serious health condition which affects the way a person can use energy (glucose) in the body.  If not addressed, prediabetes can eventually lead to a diagnosis of Type 2 diabetes. Diabetes is the number one cause of kidney failure. Kidney damage can occur in the pre-diabetic stage even before a diagnosis of diabetes. 

Prediabetes is diagnosed by having one of the following criteria by your medical provider:

Hemoglobin A1C is a lab test that identifies average blood glucose over a 3-month period by measuring the amount of glucose attached to hemoglobin molecules. 

  • A fasting blood glucose value of 100–125 mg/dL

Blood glucose is a lab that can be obtained with an over-the-counter blood glucose meter or at a lab with a prescription from your doctor. Blood glucose values provide a snapshot of how much glucose (a 6-carbon sugar that the body uses for energy) is circulating in your bloodstream. Blood glucose values change constantly in any 24-hour period and can be affected by exercise, diet, stress, or illness. 

An oral glucose tolerance test is administered at your doctor's office. This test is less common in diagnosing prediabetes. A sugary beverage is provided which contains a measured amount of glucose. 1 hour later, blood glucose is tested to determine how quickly the body can regulate glucose in the bloodstream.

Should I be tested for prediabetes?

Prediabetes testing

According to the American Diabetes Association, if you have the following risk factors, you may want to be screened for prediabetes at your next annual primary care physician visit.

  • Being physically inactive

  • Having hypertension or history of cardiovascular disease

  • Having low levels of high-density lipoprotein cholesterol (HDL) and high triglycerides

  • Having a first-degree relative with diabetes

  • Having a history of previous elevated blood glucose level or HbA1c measurement

  • Being a woman with polycystic ovarian syndrome (PCOS) 

  • Having a history of gestational diabetes or giving birth to a baby weighing more than 9lbs. 

  • Being a member of an ethnic or minority racial group.

What are the symptoms of high blood sugar and or low blood sugar?

For a person with prediabetes, high blood sugar can present with symptoms such as headache, fatigue, blurred vision, frequent urination (especially at night), irritability, inability to focus, and or increased thirst and hunger. High blood sugar is more common for people with prediabetes. Many people who are prediabetic do not feel any adverse symptoms. However, damage to vital organs such as your kidneys could already be happening in the prediabetes state. For those with chronic, uncontrolled elevated blood glucose other signs and symptoms include frequent infections, slow wound healing, numbness, pain and tingling in the hands and feet, unintentional weight loss, and or areas of darkened skin in the armpits, groin and neck. 

Low blood sugar is less common for a person with type 2 diabetes, gestational diabetes, or prediabetes, and can present as feeling confused, angry, low energy, and or hungry. Athletes with type 1 diabetes are more likely to experience low blood sugar. 

How is prediabetes medically treated?

Your primary care physician or endocrinologist will recommend the appropriate treatment if you are diagnosed with prediabetes. Medication may be necessary to stabilize blood glucose. Additionally, maintaining a healthy body weight, regular aerobic exercise, and eating a balanced diet are part of a standard medical plan to address prediabetes. If you are an athlete with prediabetes, you may benefit from a tailored plan by a Registered Dietitian Nutritionist to fuel your training. There is often misguidance and misconception that you need to cut all carbohydrates out of your diet to manage pre-diabetes and prevent diabetes. Carbohydrates broken down into glucose molecules continue to be the main source of fuel for muscles, so it is not appropriate to cut all carbohydrates in your diet. If you are diagnosed with prediabetes and are over the age of 65, a diagnosis of prediabetes may not require any lifestyle changes or medication. The risk for developing type 2 diabetes among older adults with prediabetes seems to be less than the risk for younger adults. However, because of adverse symptoms of pre-diabetes I would still encourage diet and lifestyle modifications at any age with this diagnosis. 

I’m an athlete with prediabetes. What can I do?

Assess your overall risk for type 2 diabetes using the American Diabetes Association Tool: https://diabetes.org/diabetes-risk-test. Your BMI is used as a risk factor for the development of type II diabetes. For athletes who have a high amount of muscle mass, this can put your BMI into the “overweight” category of higher than 25 kg/m2. However, your BMI does not account for your body composition of how much muscle mass versus body fat you have. Waist circumference is a better tool to assess risk. Men have a higher risk of developing diabetes if their waist circumference is more than 40 inches, while non-pregnant women have a higher risk if their waist circumference is more than 35 inches.

Here is some good news: If you’re an athlete with prediabetes, you’re already an active person! Being physically active for 150 minutes per week can positively affect your sensitivity to insulin and reduce A1C levels over time. Sixty minutes of aerobic exercise can positively affect sensitivity to insulin for up to 24 hours after your workout. Research also shows that high intensity interval (HIIT) training and weight training can reduce A1C over time. 

Being an athlete with prediabetes means that your performance may improve with minor changes to your fueling regimen. Elevated blood glucose values have been associated with slowed visual reaction time and fatigue, among other symptoms. Glucose is the preferred fuel for skeletal muscle, so when glucose builds up in the bloodstream above normal levels, it isn’t utilized as efficiently, and athletic performance can be affected.

Athlete working out

As an athlete, should I stop eating carbs if I have diabetes?

Athletes need carbohydrates as their primary source of energy. It is likely not necessary to restrict carbohydrates in the diet if you have prediabetes. Instead, athletes should focus on maintaining normal blood glucose between exercise sessions. Athletes with prediabetes should aim for 45-65% of calories coming from carbohydrates, 20-35% fat and 10-35% protein. An endurance athlete will need a larger percentage of carbs such as 65% while a strength athlete might need somewhere around 40-50% calories from carbohydrates.

Food choices play a significant role in how quickly, and how much glucose enters your bloodstream after a meal. Factors such as outdoor temperature when you are active, hormones, and type of exercise itself can have different effects on blood glucose during training. 

It may be more helpful for glucose management to shift to thinking about timing of exercise instead of focusing on carbohydrates. Exercising after meals has been shown to improve A1C values more consistently than pre-meal exercise for people with type 2 diabetes.

Speak with your healthcare provider (your primary care physician or endocrinologist), and meet with a registered dietitian nutritionist, sports dietitian, and/or certified diabetes educator to develop an individualized plan to prevent blood glucose swings, as well as adding certain foods that can stabilize blood glucose while providing optimal fuel for performance. 

Here are the top 5 nutrition-related changes to address prediabetes:

*Note: For endurance athletes training >20 hours per week, this amount of time is still much less than the time spent not training, and because risk is based on A1C (a 3-month average), nutrition recommendations in this post focus on maintaining glucose control while not training.

1. Assess the total carbohydrates in your diet.

Most athletes can benefit from assessing the balance of macronutrients (fat, protein, carbohydrates, water) in their diet. This is especially important for athletes with diabetes, as more than 65% of energy coming from carbohydrates may contribute to elevated blood glucose values. Depending on whether you’re in season, as well as your energy requirements, calculating and assessing the amount of carbohydrate in your diet may be beneficial for optimal performance and glucose management. 

For endurance athletes with training goals which include carb loading, research on athletes who are insulin-dependent supports that these athletes should aim for 1-2 days of carb loading instead of a longer, 3–7-day carb load.  

2. Aim for high fiber carbohydrates.

This advice is for in-between workouts, including recovery meals. Instead of white rice, choose a higher fiber option, like brown or wild rice. Swap in chickpea or whole wheat pasta for your white pasta. Fiber slows digestion and allows the body to regulate blood glucose. Highly processed foods and foods with added sugar tend to be low in fiber, so consider replacing most of these foods with fruits, vegetables, and high fiber grains. 

Pre-workout meals and snacks for athletes with prediabetes should contain moderate to low fiber content to reduce risk of gastrointestinal issues. 

3. Pair carbohydrate containing foods with either a high protein food, a fat, or both. 

Example: Pairing nuts with sliced apple for a snack or having a baked potato with chicken and broccoli. 

The emphasis for the prediabetic athlete should be to prioritize balanced macronutrient meals 2-4 hours before exercise in order to stabilize blood glucose for the majority of the day. 

For fueling 1 hour prior to exercise, athletes should aim for easily digested carbohydrates. Avoiding excess fat and fiber <1 hour before activity will decrease gastrointestinal distress. 

4. If overweight, consider working toward a moderate weight loss.

Studies have shown that for people with prediabetes that are overweight, a loss of 7% of body weight improved insulin sensitivity. There are safe, and unsafe ways to lose weight. A licensed healthcare provider will be able to advise whether a change in body composition may reduce diabetes risk, and how to plan a sustainable and healthy weight loss. For some athletes, even if they are considered overweight by BMI or growth chart standards, it may not be appropriate to lose weight, due to a higher portion of body weight coming from muscle. Consult your health team before beginning a weight loss regimen.

5. Consider a switch to no-carb beverages when not in training.

Juices, soda, and drinks with sugar added to them make it difficult for the body to control blood glucose and can lead to elevated glucose levels. For hydration during times that do not include training session hydration, aim for beverages that do not contain carbohydrates, as carbohydrate containing liquids increase blood glucose more rapidly than carbohydrate containing solid foods. 

In order to sustain energy levels for endurance activities, an athlete with prediabetes may consider a fueling beverage containing resistant starch for slower release of glucose than most energy drinks. 

I’d like to change, but how can I start?

Prediabetes can be controlled with diet and lifestyle modification. If you’re an athlete with prediabetes, chances are that making changes to your nutrition regimen will be the most impactful action to reduce symptoms of chronic elevated blood sugar and reduce the risk of developing type 2 diabetes. Consult with a Registered Dietitian Nutritionist to identify your preferences and motivation to create a plan to make small meaningful changes to your fueling regimen and daily routine. By managing elevated blood sugar, you are protecting your vital organs such as your kidneys from damage. Addressing pre-diabetes successfully can prevent a person from progressing to Type 2 diabetes and needing to transition to medication to manage blood sugar. 

Sources:

American Diabetes Association. “Blood Glucose and A1C: Diagnosis.” Accessed November 15, 2023. https://diabetes.org/about-diabetes/diagnosis

American Diabetes Association. “With Prediabetes, Action is the Best Medicine.” Accessed November 15, 2023. https://diabetes.org/about-diabetes/prediabetes

Cloyd, J. (2023, July 5). Integrative approaches to managing high blood sugar: Specialty testing, lifestyle modifications, and natural remedies. Rupa Health. https://www.rupahealth.com/post/integrative-approaches-to-managing-high-blood-sugar-testing-lifestyle-modifications-and-natural-remedies 

Colberg, Sheri R., "The Athlete's Guide to Diabetes" (2019). Human Movement Sciences Faculty Books.

De Filippis, E. (2023, November 11). Prediabetes. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/prediabetes/symptoms-causes/syc-20355278 

Karpinski, Christine and Rosenbloom, Christine A., "Sports Nutrition: A Handbook for Professionals, Sixth Edition" (2017).

Prediabetes? What does it mean for your kidneys?. National Kidney Foundation. (2017, March 3). http://www.kidney.org/news/kidneyCare/Summer10/PreDiabetes 

Rooney MR, Rawlings AM, Pankow JS, et al. Risk of Progression to Diabetes Among Older Adults with Prediabetes. JAMA Intern Med. 2021;181(4):511–519. doi:10.1001/jamainternmed.2020.8774

The Mayo Clinic. “A1C test” Accessed November 15th, 2023. https://www.mayoclinic.org/tests-procedures/a1c-test/about/pac-20384643

The Mayo Clinic. “Glucose Tolerance Test”. Accessed November 15, 2023. https://www.mayoclinic.org/tests-procedures/glucose-tolerance-test/about/pac-20394296

Trojian, Thomas MD; Colberg, Sheri PhD; Harris, George MD; Oh, Robert MD; Dixit, Sameer MD; Gibson, Margaret MD; Corcoran, Matthew MD; Ramey, Lindsay MD; Berg, Philip V. MS. American Medical Society for Sports Medicine Position Statement on the Care of the Athlete and Athletic Person with Diabetes. Clinical Journal of Sport Medicine 32(1): p 8-20, January 2022. | DOI: 10.1097/JSM.0000000000000906

Tuso P. Prediabetes and lifestyle modification: time to prevent a preventable disease. The Permanente Journal, 18(3):88-93, Summer 2014. DOI: 10.7812/TPP/14-002. PMID: 25102521; PMCID: PMC4116271.

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