This week’s illustration is a histogram showing the effect of different degrees of weight loss on the remission of T2DM. This is referred to in the section on Exercise in the treatment of diabetes and I have indicated it with ***
Exercise in the prevention of diabetes
There is growing awareness in the health profession that T2DM can be prevented by weight loss. Losing the equivalent of 13% of body weight reduces the risk of progression to T2DM by about 40%.
In response to the new information about the importance of weight loss for both preventing and curing T2DM, the NHS has set up a nationwide Diabetes Prevention Programme (DPP) targeted at those at high risk of T2DM – or already having “pre-diabetes”. An analysis of the first 100,000 referrals to the programme found an uptake of 56% but a disappointing completion rate of 12%. However some promising results are being achieved.
A number of studies have confirmed that diet and exercise reduce the chance of developing T2DM in susceptible people (i.e. obese people or those with insulin resistance) to as much as half the expected level. The steepest section of the effort versus effectiveness curve is seen at the lower levels of exercise. The benefit increases with greater levels of activity up to 300 minutes of moderate to vigorous exercise per week. When it comes to specific exercise types, running, cycling, resistance training and yoga have all been found to reduce the risk of developing T2DM. Exercise is as effective as medication for preventing the progression from ‘pre-diabetes’ to clinical T2DM.
It is difficult to disentangle the effects of diet and exercise in this condition which is so dependent on body weight. We can, however, be sure that any intervention that reduces body weight – which certainly includes exercise – will also reduce the incidence of T2DM. Some studies of exercise as preventative treatment have shown that almost any level of activity is beneficial. Curiously, leisure-time activity is more effective than occupational exertion.
The latest Cochrane Review looked at 12 randomised controlled trials (RCTs) of diet and exercise for over 5,000 people at high risk of T2DM. The review concluded that the effects of diet or exercise alone were relatively small, but the combination did have a significant effect, reducing the risk from 26 per cent in the control group to 15 per cent in the treated group. Additional benefits of this approach to prevention are reduction in weight, waist circumference and blood pressure.
Exercise in the treatment of diabetes
As with prevention, diet and exercise should be the centrepieces of any treatment for diabetes – aiming to reduce weight and thereby lessen insulin resistance. If this is done quickly and effectively, many patients with diabetes are cured. The loss of at least 15% of body weight should become the initial treatment goal. Studies of diet and exercise in the treatment of T2DM have indicated that nearly 50 per cent of diabetics can be cured of their disease in this way.
The most successful RCT of lifestyle management of T2DM was reported from Scotland and Newcastle in 2018, with 298 obese diabetic patients receiving either intensive weight management or their usual care. The intervention group had their medication withdrawn and were given a carefully controlled diet, completely different from the one they usually ate, for a period of 12 weeks. This was followed by a 4-week food-reintroduction phase and a further weight-management phase lasting up to 2 years, using diet and exercise programmes to help to prevent them regaining weight. After one year, 46 per cent of the intervention group had remission of their diabetes compared with only 4 per cent in the control group. There was a reduction of an amazing 86 per cent in the incidence of diabetes among those who lost 15kg or more***.
Does it always work?
For some, such an approach is too late to effect a cure – the pancreas is already exhausted and cannot keep up with the body’s demands. Nevertheless, diet and exercise enhance the effects of other treatments and sometimes makes them unnecessary. Most diabetics need tablets to reduce their blood sugar to reasonable levels and some require insulin. Diet and exercise, combined with weekly counselling, has been shown to reduce considerably the need for medication even in those not cured. Results were best for those who lost the most weight or who started the programme with less severe or with newly diagnosed diabetes. Those who do not achieve remission with diet and exercise still have much to gain from regular physical activity. Exercise can greatly improve diabetic control. Regular exercise improves blood sugar levels, reduces HbA1C (an important marker of diabetes), improves blood lipids, lowers blood pressure and increases physical fitness. Better sexual function and quality of life are additional benefits. The response to exercise for diabetic control is, like the response for prevention, related to dose of exercise. Both aerobic and combined aerobic and resistance exercise have these effects but not resistance exercise on its own.
Diabetics who respond favourably to diet and exercise and maintain their improved control or remission over two years or more have been shown to have an increase in pancreatic volume suggesting that their response may be mediated partly through recovery of the ability of the pancreas to produce insulin.
Exercise in the prevention of the complications of diabetes
Intensive lifestyle interventions have many other benefits for the type 2 diabetic. These include better glucose and lipid control, improved blood pressure, less sleep apnoea, lower liver fat, less depression, less urinary incontinence, less severe kidney disease and less retinopathy (i.e. blindness and sight loss), reduced need of diabetes medications, maintenance of physical mobility, improved quality of life, less knee pain, improved sexual function, lowered inflammation and reduced over-all health costs. The Whitehall study has shown an increase in life expectancy for diabetics who take regular exercise and this has been confirmed in a study of the cycling habits of diabetics followed over 15 years. Cycling 150 to 300 minutes per week was associated with 35% lower mortality than non-cyclists.
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