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HIIT improves heart function for Type 2 diabetics

Analysis by Dr. Joseph Mercola Fact Checked

hiit improves heart function for type 2 diabetics

Story at-a-glance -

  • High-intensity interval training (HIIT), a type of exercise that combines brief sessions of high-intensity activity with bouts of rest, improved heart function in people with Type 2 diabetes
  • Adults with Type 2 diabetes who engaged in HIIT for three months had improved left ventricular exercise response (the left ventricle is the lower left chamber of the heart)
  • The HIIT group also increased their VO2 max, which is the maximum amount of oxygen your body can handle while exercising; this can be utilized as a measure of cardiovascular fitness, by 15%
  • Other research suggests HIIT improves aerobic fitness and hemoglobin A1c (HbA1c), a measure of damage caused by elevated blood glucose, in diabetics

Type 2 diabetes is associated with reduced left ventricular function in the heart.1 The left ventricle is the lower left chamber of the heart, and if it gets bigger and is unable to contract enough to pump blood throughout the body, it can lead to heart failure.2 In turn, at least one-third of patients with heart failure also have diabetes, showing the strong association one disease has with the other.3

Fortunately, there are steps you can take to improve diabetes outcomes, including in the case of your heart. High-intensity interval training (HIIT), a type of exercise that combines brief sessions of high-intensity activity with bouts of rest, has emerged as one of the most efficient workouts available, and this holds true for improving heart function in diabetics as well.

Three months of HIIT improves heart function in diabetics

For people with Type 2 diabetes, exercise is a must for improving and maintaining health, and adding HIIT for three months may be enough to ward off some of the damage that this condition does to your heart, according to research published in Medicine & Science in Sports & Exercise.4

The study involved 11 middle-aged adults with Type 2 diabetes who engaged in HIIT for three months or no training at all. The exercise sessions were 25 minutes long, of which 10 minutes was very high intensity.5

The HIIT group increased their VO2 max, which is the maximum amount of oxygen your body can handle while exercising. While their body composition was not altered, the VO2 max can be utilized as a measure of cardiovascular fitness by 15%. Additionally, the exercise led to improved left ventricular exercise response and heart function.

“These data suggest that HIIT can improve LV [left ventricle] filling and emptying during exercise and reverse early cardiac consequences of type 2 diabetes,” the authors concluded.6 Also encouraging, HIIT appeared to be a safe form of exercise and was well received by the study participants, with 80% sticking with the program over the three-month period.7 Study author Chris Baldi explained in a news release:8

"There are two important clinical implications of this work. The first, that adults with type 2 diabetes will adhere to high-intensity interval training and are capable of comparable increases in aerobic capacity and left ventricular exercise response as those reported in non-diabetic adults.

Secondly, high-intensity exercise is capable of reversing some of the changes in heart function that seem to precede diabetic heart disease."

HIIT has many benefits for people with Type 2 diabetes

Improved heart function is just one benefit that people with Type 2 diabetes may glean from participating in HIIT. In a review of 14 studies, HIIT proved to be at least equivalent, benefit-wise, to typical moderate-intensity exercise, with researchers suggesting HIIT be considered as a suitable exercise intervention for helping people with Type 2 diabetes.9

Among the benefits they revealed were improved glycemic control, body composition, aerobic fitness, blood pressure and lipidemia (the presence of excess fats in the blood) measures. Other research suggests HIIT improves aerobic fitness and hemoglobin A1c (HbA1c), a measure of damage caused by elevated blood glucose, in diabetics.10

When a 12-week HIIT exercise program was combined with nutritional education, people with Type 2 diabetes again experienced benefits, including improvements in cardiometabolic measures as well as increases in quality of life parameters such as physical function, pain, general health, vitality, mental health and social function.11

In another study yielding impressive results, sedentary and overweight or obese women with Type 2 diabetes were assigned to a running-based HIIT program or a nonexercise group. Not only were the women able to reduce their daily dosages of antihyperglycemic and antihypertensive medication during follow-up, but they also had improvements in:12

Fasting glucose

HbA1c

Systolic blood pressure

HDL cholesterol

Triglycerides

Endurance performance

Body weight

Waist circumference

Subcutaneous fat

Body mass index (BMI)

The researchers also noted the improvements occurred with a weekly time commitment 25% to 56% lower than the minimal recommended in current guidelines. “These findings suggest that low-volume HIT may be a time-efficient intervention to treat T2DM [Type 2 diabetes mellitus] women,”13 the authors said.

Is HIIT better than continuous exercise training for diabetes?

It’s clear that regular exercise is a key part of treating Type 2 diabetes, but which type of exercise is best — HIIT or moderate-intensity continuous training (MICT)? In one study, HIIT came out clearly on top, at least in mice.

The researchers compared 10 weeks of HIIT with MICT, hypothesizing that HIIT would lead to greater benefits on glycemic control due to superior improvements to mitochondrial function, as HIIT may be a strong activator of mitochondrial biogenesis, which is important for longevity.

On the other hand, the researchers reasoned, “Mitochondrial impairment has been linked to insulin resistance, and consequently, improvement of mitochondrial function may restore skeletal muscle insulin signaling.”14

What they found was that HIIT did improve glucose metabolism more efficiently than MICT in diabetic mice, although the improvements were not necessarily related to mitochondrial changes. Another study involving adults with Type 2 diabetes showed HIIT to be more effective than MICT in terms of normalizing oxidative stress.15

In other research, when HIIT was performed twice a week for 16 weeks, it was found to reduce abdominal fat mass in postmenopausal women with Type 2 diabetes more effectively than MICT. Researchers suggest it could therefore be “proposed as an alternative exercise training program for this population.”16

It’s worth noting, too, that people may have an easier time adhering to HIIT workouts due to the lower time commitment involved. Engaging in HIIT sessions of under 15 minutes per session has been found to be enough to benefit cardiometabolic risk factors in people with risk factors for Type 2 diabetes.17

How short can HIIT sessions be?

It can be hard to believe that shorter workouts can lead to similar or even greater gains than longer workouts, but the secret lies in the intensity. By pushing your body to near its maximum, you reap greater benefits faster. How much faster?

One single minute of strenuous activity within a 10-minute exercise session is as effective as working out for 50 minutes at a moderate pace, according to one study.

“Twelve weeks of brief intense interval exercise improved indices of cardiometabolic health to the same extent as traditional endurance training in sedentary men, despite a fivefold lower exercise volume and time commitment,” the researchers explained.18

HIIT also works quickly to improve your health. Unfit but otherwise healthy middle-aged adults were able to improve their insulin sensitivity and blood sugar regulation after just two weeks of interval training (three sessions per week).19

A follow-up study also found that interval training positively impacted insulin sensitivity. The study involved people with Type 2 diabetes, and just one interval training session was able to improve blood sugar regulation for the next 24 hours.20

If you’re at risk of diabetes, get moving now

Your fasting insulin and glucose levels are blood tests I recommend receiving annually to help you gauge your diabetes risk. Your fasting insulin level reflects how healthy your blood glucose levels are over time. You'll want your fasting insulin level to be between 2 and 4. The higher your level, the worse your insulin sensitivity is.

A fasting glucose level below 100 mg/dl suggests you're not insulin resistant, while a level between 100 and 125 confirms you have prediabetes. If this, or your A1C level, confirms you either have or are at risk of prediabetes or diabetes, the time to take action is now. You might also find a hip-to-waist size index chart helpful in determining your level of risk.

If you have Type 2 diabetes, prediabetes or are at risk of developing either of these conditions, changing your lifestyle can lead to significant benefits. During the 2.8-year Diabetes Prevention Program study, for instance, lifestyle interventions were found to be more effective than the diabetes drug metformin at preventing or delaying the development of diabetes in people at high risk of the disease.21

After the initial study, those who made dietary changes and exercised at moderate intensity for 15 minutes daily were 58% less likely to develop diabetes compared to a placebo group.22 Those taking metformin were 31% less likely to develop the disease. A follow-up study monitored the group for 15 years — and lifestyle interventions were still more effective than metformin at preventing diabetes.23

Nutrition and lifestyle modifications should be the foundation of your diabetes prevention and treatment plan, and although the study didn’t look into HIIT, it’s possible that engaging in this form of exercise may have led to even greater benefits. In addition to these activities, strength training is also an effective form of exercise for diabetes.

A surefire plan to prevent diabetes

What does a comprehensive plan to send diabetes packing look like? See below for the essential tips to prevent this common condition, or help you recover if you’ve already been diagnosed:

Severely restrict (or eliminate) all forms of sugar and grains in your diet — Following my Nutrition Plan will help guide you through the necessary dietary changes. Also avoid excessive protein, as your body converts that to sugar in your liver, which can sabotage your ability to control insulin resistance. Excess protein may even be more damaging to your health than excess carbs.

Make sure you’re eating the right kinds of fats — Marine-based omega-3 fats are particularly important for optimal health. To learn more about the ins and outs of dietary fats — which ones are beneficial and which ones need to be avoided to protect your health — be sure to read my book, “Superfuel,” co-written with James DiNicolantonio, Pharm.D.

Try fasting — Fasting is yet another powerful treatment strategy for diabetes. To learn more, see my interview with Dr. Jason Fung, author of “The Diabetes Code: Prevent and Reverse Type 2 Diabetes Naturally.”

Exercise and stay active — To get started, review my Peak Fitness program for tips and guidelines. Remember to include HIIT and strength training in your program, and also stay as active throughout each day, avoiding excessive sitting as much as possible.

Optimize your vitamin D level — Research has demonstrated a clear relationship between your vitamin D status and insulin resistance, showing vitamin D is necessary for normal insulin secretion and improves insulin sensitivity.

Optimize your gut microbiome — Multiple studies have shown obese individuals have different gut bacteria than lean people, and that certain microbes tend to promote obesity. You can reseed your body with beneficial bacteria by eating traditionally fermented foods and/or taking a high-quality probiotic supplement.

Address any underlying emotional issues and/or stress — Noninvasive tools like the Emotional Freedom Techniques (EFT) can be helpful and effective.

Get eight hours of sleep every night — Research shows lack of sleep increases your risk of both weight gain and diabetes. One 2015 study linked daytime sleepiness and napping (which tends to be a sign of insufficient sleep) with a 53% increased risk for Type 2 diabetes,24 so be sure you’re getting proper shuteye.