However, increased activity conferred no additional benefit when combined with the diet intervention.
The study assessed 593 adults aged 30—80 years in whom type 2 diabetes had been diagnosed five to eight months earlier. Of these, 99 were assigned to usual care, 248 to diet advice only, and 246 to diet advice plus exercise. Usual care patients received an initial dietary consultation plus follow-up every six months. Diet-only group patients were given a dietary consultation every three months with additional nurse support each month. Diet and exercise patients received the same as diet only patients but were also asked to do 30 minutes of brisk walking five times a week (with activity assessed by pedometers that showed good adherence).
The researchers found that in the usual care group, blood sugar control had worsened, with mean HbA1c (a method of assessing blood sugar control) levels increasing from 6.72per cent to 6.86 per cent over six months, before falling back to 6.81 per cent at 12 months. In the diet advice group, HbA1c fell from a mean 6.64 per cent pre-intervention to 6.57 per cent at six months and 6.55 per cent at 12 months. Exercise did not confer additional benefit on top of the diet advice, apart from in those patients with the highest HbA1c, insulin-resistance, or body-mass index at baseline.
Dr Andrews said: “These findings suggest that intervention at this early stage should focus on improving diet, since the additional cost of training health-care workers to promote activity might not be justified.”
The researchers add there could be a number of reasons for the apparent lack of effect of increased activity: that it was not intense enough, or that it was too early in the disease process for exercise to show an effect.
It is also possible that those in the diet and exercise group modified their behaviour and diluted the effect of both interventions, for example, rewarding themselves with extra food due to increased exercise.
Dr Andrews concluded: “Further research is needed to clarify whether more intensive or different types of activity, or activity advice offered at a later stage of diabetes will add benefits to diet interventions, or whether benefits of activity interventions will become more apparent after one year.”
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Paper: Diet or diet plus physical activity versus usual care in patients with newly diagnosed type 2 diabetes: the Early ACTID randomised controlled trial; Dr RC Andrews PhD, AR Cooper PhD, AA Montgomery PhD, AJ Norcross MSc, Prof TJ Peters PhD, Prof DJ Sharp PhD, N Jackson BSc, K Fitzsimons PhD, J Bright MBA, K Coulman MSc, CY England BSc, J Gorton BSc, A McLenaghan RN, E Paxton BSc, A Polet BSc, C Thompson Dip HE, Prof CM Dayan FRCP. The Lancet, Early Online Publication, 25 June 2011