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The Prediabetes Nutritionist

How Exercise Helps Prediabetes and Type 2 Diabetes

If you’re trying to lower your blood sugar and essentially reverse prediabetes or manage type 2 diabetes, exercise, when done correctly, can be a powerful tool in your arsenal! 

Exercise is beneficial in prediabetes and type 2 diabetes because it lowers blood glucose and body fat percentage, increases insulin sensitivity, improves lipid profile and blood pressure, and reduces inflammation even without weight loss. 

While any type of physical activity is better than being sedentary, evidence suggests you need structured physical activity – exercise – to achieve blood sugar balance and lower the risk of heart disease.

Keep reading to learn the types and how much exercise you need to improve blood sugar control in prediabetes and type 2 diabetes. 

Physical Activity and Exercise are Different

We often use ‘physical activity’ and ‘exercise’ interchangeably. But it turns out that there’s a huge difference between the two, at least in therapeutic terms. 

According to Zanuso and colleagues (2010), “physical activity refers to any bodily movement produced by skeletal muscles that results in an expenditure of energy (expressed in kilocalories) and include a broad range of occupational, leisure and daily activities”. Physical activity includes gardening, leisure walks and cleaning.

Conversely, “exercise refers to planned or structured physical activity. It involves repetitive bodily movements performed to improve or maintain one or more of the components of physical fitness: aerobic capacity (or endurance capacity), muscle strength, muscular endurance, flexibility and body composition.” Exercise includes running, jogging, brisk or power walking and weightlifting. 

So, although physical activity is vital for health and wellbeing, exercise is the type of physical activity that provides therapeutic benefits in prediabetes and type 2 diabetes. 

How exercise benefits prediabetes and type 2 diabetes

Exercise has several fantastic benefits for people with prediabetes and type 2 diabetes. 

1 | It increases metabolism

The body generally burns more energy during exercise than when it’s resting. Remarkably, this effect is not limited to active exercise; it continues for many hours post-exercise. A study on overweight young adults showed that resistance training, including one or three sets of 10 different exercises, increased energy expenditure by 5% for 72 hours. Remarkably, one set was as effective as three sets in raising energy expenditure (Heden et al., 2011).

2 | It increases glucose uptake and insulin sensitivity in the muscles.

Insulin normally instructs the muscles to absorb glucose from the bloodstream. In people with prediabetes and type 2 diabetes, the muscles don’t respond appropriately to insulin and can’t absorb glucose. 

However, during exercise, the muscles can absorb glucose from the bloodstream as they would in healthy individuals. This means that exercise activates other pathways that enable muscles to absorb glucose from the bloodstream despite being unresponsive to insulin (Standford and Goodyear, 2014). 

3 | It makes the mitochondria in the muscles more functional

The mitochondria – energy-producing structures in all cells – are smaller, damaged and dysfunctional in people with prediabetes. Studies show that aerobic exercise increases the amount and activity of mitochondria, thereby increasing muscle insulin sensitivity and whole-body health in people with diabetes (Standford and Goodyear, 2014).

4 | It improves lipid profile and lowers heart disease risk factors

People with prediabetes have a 15% higher risk of heart disease than healthy individuals due to impaired lipid profiles, including high ‘bad’ low-density lipoprotein (LDL) cholesterol, high cholesterol and lower levels of ‘good’ high-density lipoprotein (HDL) cholesterol.

 A meta-analysis of 42 randomised controlled trials found that structured exercise – aerobic, resistance training or a combination of both – reduced glycated haemoglobin (HbA1c) by 0.51%, fasting blood glucose by 0.70 mmol/L, blood pressure by 2.2-2.4 mmHg, LDL cholesterol by 0.16mmol/L, waist circumference by 0.57cm and body mass index by 0.42. HDL cholesterol increased by 0.04 mmol/L (Hayashino et al., 2012).

The reduction in blood pressure translates to an 11.8-25.4% reduction in heart disease, while the decrease in LDL and increase in HDL cholesterol translates to a 4.2% and 3.7-5.5% reduction in heart disease, respectively (Hayashino et al., 2012). 

5 | It reduces body and visceral fat 

Exercise improves body composition by reducing overall body fat, visceral fat (fat around the organs) and increasing lean body mass. The reduction in body fat percentage reduces insulin resistance and increase omentin-1 – a protein present in fat tissues. Lower levels of omentin-1 are associated with a higher risk of diabetes (Amanat et al., 2020). 

6 | It reduces inflammation

Prediabetes and type 2 diabetes are strongly associated with inflammation and oxidative stress – when the body produces too many free radicals without enough antioxidants. High levels of inflammatory proteins such as c-reactive protein, interleukin-1beta and tumour necrosis factor-alpha and inflammatory cells are present in the circulation and tissues, increasing the risk of eye, kidney, and nerve damage. 

Exercise increases the levels of interleukin-6, which reduces the levels of inflammatory proteins and increases the levels of anti-inflammatory proteins (Pedersen, 2017). 

7 | It improves mental health and quality of life

A meta-analysis showed that individuals with prediabetes have a moderately increased risk of depression than healthy individuals (Chen et al., 2016). And compared to people with only prediabetes, those with anxiety and depressive symptoms and prediabetes have higher odds of progressing to type 2 diabetes (Deschenes et al., 2016). 

Furthermore, people with diabetes have a higher risk of psychological conditions, including depression, eating disorders, anxiety and severe mental illness, than the general population, with depression rates two-fold higher in people with type 2 diabetes. The evidence for the benefits of exercise in improving mental health in people with type 2 diabetes is conflicting.

Some studies show that structured exercise has similar therapeutic effects to antidepressants for treating mild to moderate depression in type 2 diabetes (Knapen et al., 2014). Consistent with this finding, a systematic review showed that aerobic exercise improves anxiety symptoms, while resistance training significantly improves depressive symptoms (van der Heijden et al., 2013). 

However, a randomised controlled trial found that no exercise was superior to either resistance training or a combination of aerobic exercise for improving mental health (Reid et al., 2010). 

What is the best type of exercise for prediabetes and type 2 diabetes?

Based on scientific evidence, aerobic and resistance training are the two types of structured exercises that provide the most benefit in prediabetes and type 2 diabetes. 

Aerobic exercise involves the repeated and continuous movement of large muscles. It includes exercises such as walking, cycling, jogging, and swimming. Conversely, resistance training includes exercises with free weights, weight machines, bodyweight, or elastic resistance bands (Colberg, 2016). 

Both types of exercise reduce HbA1c, increase muscle insulin sensitivity, lower body fat, blood pressure and fasting blood glucose, and improve lipid profiles. Resistance training has the added benefit of improving bone mineral density (Colberg, 2016).

It is essential to perform both exercises at a moderate-high intensity for a reasonable duration to get optimum benefits. Th evidence for the effects of low-intensity exercises on blood glucose control is mixed. Some studies show clinically significant benefits, while others do not. However, for sedentary individuals, low-intensity supervised exercise done at high volume lowers heart disease risk (Balducci et al., 2012). 

A meta-analysis of 47 randomised controlled trials, including 23 studies of structured exercise training and 24 studies with physical activity, found that structured exercise durations of more than 150 minutes per week were linked to greater reductions in HbA1c than durations less than 150 minutes, 0.89% vs. 0.36%, respectively (Umpierre et al., 2011). Interestingly, physical activity only reduced HbA1c when combined with calorie restriction. 

A more recent meta-analysis of 24 trials investigated the effects of resistance training at varying intensities on HbA1c, insulin and blood glucose levels in individuals with type 2 diabetes. The study included 962 participants, 491 in the exercise group and 471 in the control group. 

The researchers considered a one-repetition maximum between 20% and 75% as low-to-moderate intensity, while a one-repetition maximum between 75% and 100% was considered high-intensity. Consistent with previous evidence, high-intensity exercise decreased HbA1c more significantly than low-to-moderate exercises, but only high-intensity resistance exercise decreased insulin levels (Liu et al., 2019). 

Based on the available evidence, American guidelines recommend a minimum of 150-300 minutes of moderate exercise or 75-100 minutes of intense activity per week to improve glycaemic control, manage weight and reduce the risk of cardiovascular disease (Sigal et al., 2006). 

Resistance training that targets all major muscle groups should be performed at least three times per week. Ideally, the exercise should involve three sets of eight to ten repetitions using weights that cannot be lifted more than eight to ten times. 

Aerobic and resistance training should be distributed over at least three days with no more than two consecutive days without exercise. 

The American Diabetes Association recommends flexibility exercises, including stretching, yoga, Pilates, and tai chi, to maintain healthy joints. However, flexibility exercises must not replace aerobic and resistance exercises because they do not improve glucose control, body composition or insulin sensitivity (Colberg et al., 2016). 

Type of exerciseAerobicResistance
Description and examplesAny exercise that uses large muscle groups e.g., walking, cycling or swimmingAny exercise that uses resistance machines, free weights, resistance bands or body weight 
How hard should you exercise?Moderate to vigorous Moderate e.g., 15 repetitions of an exercise that can be repeated no more than 15 times to vigorous (6-8 repetitions of an exercise that can be repeated no more 6-8 times)
How long should you exercise?At least 150 mins per week at moderate to vigorous intensity or 75 mins per week of vigorous activity Complete 1-3 sets of 8-10 exercising, performing 10-15 repetitions per set. Exercises set should be completed to near fatigue 
How often should you exercise?3-7 days per week with no more than two consecutive days without exerciseA minimum of two non-consecutive days per week but preferably three.
The American Diabetes Association’s Recommendation for Aerobic and Resistance Training in Prediabetes and Type 2 Diabetes.

Now you know the health and metabolic benefits of exercise in prediabetes and type 2 diabetes. 

It is vital to speak with your doctor or healthcare team before starting exercise, particularly if you have type 2 diabetes with complications, as some exercises may be unsuitable. 

Exercise needs to be part of your lifestyle if you want to get the most of it. If you’ve been inactive for a long time, you shouldn’t start intense exercise immediately as it can result in injury; just moving more is good enough to begin. 

Once you build confidence and endurance, I’ll highly recommend working with an exercise specialist to develop a tailored, progressive plan to improve your blood glucose control. 

REFERENCES

  1. Zanuso, S., Jimenez, A., Pugliese, G., Corigliano, G., & Balducci, S. (2010) Exercise for the management of type 2 diabetes: a review of the evidence. Acta Diabetologia; 47: 15-22.
  2. Standford, K.I., and Goodyear, L.J. (2014) Exercise and type 2 diabetes: molecular mechanisms regulating glucose uptake in skeletal muscles. Advances in Physiology Education; 38(4): 308-314. 
  3. Heden, T., Lox, C., Rose, P., Reid, S., Kirk, E.P. (2011) One-set resistance training elevates energy expenditure for 72h similar to three sets. European Journal of Applied Physiology; 111(3): 477-484. 
  4. Hayashino, Y., Jackson, J.L., Fukumori, N., Nakamura, F., & Fukuhara, S. (2012) Effects of supervised exercise on lipid profiles and blood pressure control in people with type 2 diabetes mellitus: a meta-analysis of randomised controlled trials. Diabetes Research and Clinical Practice, 98(3): P349-360.
  5. Amanat, S., Ghari, S., Dianatinasab, A., Fararouei, M., & Dianatinasab., M (2020) Exercise and type 2 diabetes. In: Physical exercise for human health, advances in experimental medicine and biology. J. Xia (ed.). Available: https://doi.org/10.1007/979-981-15-17921_6
  6. Pedersen, B.K. (2017) Anti-inflammatory effects of exercise: role in diabetes and cardiovascular disease. European Journal of Clinical Investigation; 47(8): 600-611.
  7. Chen, S., Zhang, Q., Dai, G., Hu, J., Zhu, C., Su, L., & Wu, X. (2016) Association of depression with prediabetes, undiagnosed diabetes, and previously diagnosed diabetes: a meta-analysis. Endocrine; 53(1): 35-46. 
  8. Balducci, S., Zanuso, S., Cardelli, P., Salvi, L., Bazuro, A., Pugliese, L., Maccora, Ca., Lacobini, C., Conti, F.G., Nicolucci, A., Pugliese, G. (2012) Effect of high-versus low-intensity supervised aerobic and resistance training on modifiable cardiovascular risk factors in type 2 diabetes: the Italian diabetes and exercise study (IDES). PLoS One; 7(11): e49297/ 
  9. Umpierre, D., Ribeiro, P.A.B., Kramer, C.K., Leitao, C.B., Zucatti, A.T.N., Azevedo, M.J., Gross, J.L., Ribeiro, J.P., Schaan, B.D. (2011) Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis. JAMA, 305 (17): 1790-9. 
  10. Deschenes, S.S., Burns, R.J., Graham, E., Schmitz, N. (2016) Prediabetes, depressive and anxiety symptoms, and risk of type 2 diabetes: A community-based cohort study. Journal of Psychosomatic Research; 89: 85-90. 
  11. Knapen, J., Vancampfort, D., Morien, Y., & Marchal, Y. (2014) Exercise therapy improves both mental and physical health in patients with major depression. Disability and Rehabilitation, DOI: 10.3109/09638288.2014.972579.
  12. Van der Heijden, M.M., van Dooren, F.E., Pop, V.J., & Pouwer, F. (2013) Effects of exercise training on quality of life, symptoms of depression, symptoms of anxiety and emotional wellbeing in type 2 diabetes mellitus: a systematic review. Diabetologia; 56(6): 1210-1225.
  13. Reid, R.D., Tulloch, H.E., Sigal, R.J., Kenyy, G.P., Fortier, M., McDonnell, L., Wells, G.A., Boule, N.G., Phillips, P., Coyle, D. (2010) Effects of aerobic exercise, resistance exercise or both, on patient-reported health status and wellbeing in type 2 diabetes mellitus: a randomised trial. Diabetologica; 53(4): 632-40.
  14. Colberg, S.R., Sigal, R.J., Yardley, J.E., Riddell, M.C., Dunstan, D.W., Dempsey, P.C., Horton, E.S., Castorino, K., & Tate, D.F. (2016) Physical activity/exercise and diabetes: a position statement of the American Diabetes Association. Diabetes Care; 39 (11): 2065-2079.
  15. Liu, Y., Ye, W., Chen, Q., Zhang, Q., Kuo, C-H., Korivi, M. (2019) Resistance exercise intensity is correlated with attenuation of HbA1c and insulin in patients with type 2 diabetes: a systematic review and meta-analysis. International Journal of Environmental Research and Public Health; 16(1): 140. 

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