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Exercise ‘has limited value’ in patients with poorly controlled type 2 diabetes

The benefit people obtain from exercise in terms of glycaemic control and aerobic fitness depends on their pre-training glycaemic levels, such that patients with poorly controlled type 2 diabetes are unlikely to see improvements, according to a Danish study.

The study

Researchers monitored 105 men, 56 with impaired glucose tolerance and 49 with type 2 diabetes, who underwent a 12 - 16-week aerobic exercise training programme. The study participants had an average age of 61 years and were overweight or obese, with a mean body mass index of 33 kg/m2. The training programme consisted of moderate-intensity exercise training for 60 minutes per day, five days per week.

Participants’ aerobic fitness, measured by maximal oxygen uptake (Vo2max), and glycaemic control measured by HbA1c levels, fasting glucose and oral glucose tolerance test (OGTT) response, were recorded pre- and post-training.

The findings

Overall, participants lost a mean of 4.6 kg in weight, with a reduction of 1.9% of whole body adiposity, and had an improvement of Vo2max of 0.23 L/min, a reduction in fasting plasma glucose of 0.35 mmol/L and a reduction in 2-hour OGTT of 0.8 mmol/L.

Further analysis showed pre-training hyperglycaemia predicted worse training-induced improvements in glycaemic control. For each 1 mmol/L increase in pre-training 2-hour glucose level above 13.1 mmol/L, there was a 0.2 mmol/L loss of improvement in 2-hour glucose level.

Similarly, for every 1% increase in pre-training HbA1c level above 6.2%, there was a 0.2% point loss of improvement in HbA1c level after exercise.

Pre-training HbA1c level also predicted the improvement in post-training aerobic fitness, such that each 1% point increase in baseline HbA1c related to a 0.11 L/min loss in improvement in Vo2max after exercise.

What this means to GPs

The authors commented: ‘Although moderate-intensity aerobic exercise can improve glycaemic control, individuals with ambient hyperglycaemia are the most likely to be non-responders.’

They concluded: ‘The clinical relevance of these new findings is paramount and highlights the need to understand the metabolic “non-responder”.’

‘Because chronic hyperglycaemia (>6.2% HbA1c; >13.1 mmol/L glucose level) potentially predicts a poor therapeutic effect of aerobic exercise on glycaemic control and fitness, using exercise to treat patients with poorly controlled [type 2 diabetes] may have limited chances of a successful outcome.’

JAMA Intern Med 2013; available online 1 July


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