14 OCTOBER

I recently commented on an article published in the Journal of the American Medical Association that very well described why an excessive amount of liver fat is linked with poor cardiometabolic health and is a strong predictor of type 2 diabetes risk. It is generally accepted that increasing physical activity levels could decrease liver fat but few studies have sought to determine which type of physical activity most strongly influences liver fat accumulation. Also, few of these studies have been conducted in patients with type 2 diabetes.

In the latest issue of Diabetologia, investigators from the Newcastle University in the United Kingdom present results of their randomized clinical trial that determined the impact of high-intensity interval training (HIIT) on liver fat, blood glucose control and cardiovascular function in patients with type 2 diabetes.  In this study, 28 patients with type 2 diabetes who were treated with metformin were randomized to a 12-week period of HIIT (3 sessions per week on non-consecutive days) or standard care. According to the authors, “HIIT refers to brief intervals of rigorous physical activity interspersed with periods of low physical activity or rest, and elicits a strong cardiac response compared with moderate continuous exercise”. In this trial, HIIT was performed on cycle ergometers and each session included five high-intensity intervals of 2-3 minutes (interval periods increased as the trial progressed). Results of this study showed that patients in the HIIT group significantly improved their blood glucose control (without changing their medication or diet), improved their cardiac structure and function (defined as magnetic resonance imaging [MRI]-measured systolic and diastolic function) and decreased their amount of liver fat (which was also measured by MRI) by a staggering 39%. Interestingly, changes in liver fat were associated with changes in blood glucose control.

It has been estimated that patients with type 2 diabetes are twice as likely to develop cardiovascular diseases than people without diabetes. Although the benefits of physical activity for these patients have been known for decades, by showing that HIIT could improve several cardiovascular risk factors over a relatively short period of time, results of this study could have an important impact for the management of these patients. It should be noted, however, that the trial included a limited number of patients and that most of them were around 60 years of age. Longer trials including a broader range of patients with various levels of glycemic control are warranted to better determine the impact of HIIT on blood glucose control in patients with type 2 diabetes. For these patients (and for virtually everybody for that matter), some exercise will always be better than none and more is obviously better than some. However, as type 2 diabetes is a disease that could be challenging to manage in many cases, adding HIIT to hypoglycemic drugs and dietary management may represent a very promising strategy for mobilizing liver fat, improving blood glucose control and decrease cardiovascular risk in these patients.