A systematic review published in 2019 explored the effect of Nordic Walking on improving glycaemic control. Overall, it highlighted a significant reduction in OGTT-2h and HbAc1 in obese and T2DM participants respectively. Interestingly, a supervised Nordic Walking program with a shorter duration (6 weeks) was thought to lead to significant improvements in both glucose blood profile and glucose tolerance in middle-aged men .
A meta-analysis which was also published in 2019 evaluated the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on cardiovascular risk factors including glucose metabolism. Some of the studies identified HIIT as being superior in reducing insulin resistance, whereas others showed no difference between the two. 
Resistance training was found to improve fasting insulin levels in comparison to endurance training during a systematic review (effect size = 3.5) and meta-analysis published in 2015. Even though generally lower effect size than resistance training, the inclusion of endurance training was more effective when performed at high intensity or in an interval training style. 
A systematic review published in 2018 aimed to establish the effects of exercise training on liver function in adults who are overweight or exhibit fatty liver disease.  Data from 11 exercise studies was analysed (of which some included dietary intervention); there was a significant insulin reduction in 5 groups but no change in 6 groups, with 1 group showing an increase in insulin. The effect size was moderate but was not significant (SMD −0.47 (−1.07 to 0.13), p=0.13, I2=63%). The analyses suggest that it is calorie burning that elicits reductions in liver fat, reduced fat storage, possibly reduced liver enzymes and the sum of all of this is in fact improved glycaemic control.
In 2021, another systematic review examined the found that exercise interventions reduced insulin resistance SMD = −0.34 [−0.49, −0.18], p < 0.0001, I2 = 48%, 37 study arms .
Quality of Evidence
A – Consistent evidence from meta-analysis and systematic review
Strength of recommendation
1 – Based on the existing evidence, clinical opinion is that all or most patients will be best served by following this piece of evidence
Exercise interventions are likely to result in improved glycaemic control in overweight or people living with obesity. Findings from across the systematic reviews and meta-analyses in favour of exercise to reduce insulin resistance. Exercise interventions can, therefore, be recommended to most people, in most circumstances, to improve glycaemic control. It is unclear however, what form of exercise intervention would best achieve improved glycaemic control.
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2. Su, L., Fu, J., Sun, S., Zhao, G., Cheng, W., Dou, C., & Quan, M. (2019). Effects of HIIT and MICT on cardiovascular risk factors in adults with overweight and/or obesity: A meta- analysis. PloS one, 14(1), e0210644. https://doi.org/10.1371/journal.pone.0210644
3. Clark J. E. (2015). Diet, exercise or diet with exercise: comparing the effectiveness of treatment options for weight-loss and changes in fitness for adults (18-65 years old) who are overfat, or obese; systematic review and meta-analysis. Journal of diabetes and metabolic disorders, 14, 31. https://doi.org/10.1186/s40200-015-0154-1
4.Smart, N. A., King, N., McFarlane, J. R., Graham, P. L., & Dieberg, G. (2018). Effect of exercise training on liver function in adults who are overweight or exhibit fatty liver disease: a systematic review and meta-analysis. British journal of sports medicine, 52(13), 834–843. https://doi.org/10.1136/bjsports-2016-096197
5.Battista, F., Ermolao, A., van Baak, M. A., Beaulieu, K., Blundell, J. E., Busetto, L., Carraça, A. V., Encantado, J., Dicker, D., Farpour-Lambert, N., Pramono, A. & Bellicha, A. (2021). Effect of exercise on cardiometabolic health of adults with overweight or obesity: Focus on blood pressure, insulin resistance, and intrahepatic fat—A systematic review and meta-analysis. Obes Rev Jul;22 Suppl 4(Suppl 4):e13269. https://doi.org/10.1111/obr.13269