Pumping weights five times a week can reduce the risk of type 2 diabetes by a third and if combined with aerobic exercise can curt the risk by almost 60 per cent, a study has found.
Even small amounts of weight training had an effect on type 2 diabetes, it was found, which is important for those people who cannot cope with aerobic exercise, the authors said.
However, combining both weight training and aerobic exercise gave the biggest benefits, they said.
Type 2 diabetes affects around two million people in Britain, many of which do not know they have it. It is largely associated with being overweight and substantially increases the risk of suffering a heart attack.
The researchers from Havard School of Public Health in Boston, America and the University of Southern Denmark, followed 32,000 men for 18 years.
The benefits of weight training and aerobic exercise were independent of each other, meaning participants reduced their risk of diabetes by only doing one, but the combined effects were greater, it was found.
The findings were published online in Archives of Internal Medicine.
Lead author Anders Grøntved, visiting researcher in the Department of Nutrition at HSPH and a doctoral student in exercise epidemiology at the University of Southern Denmark, said: "Until now, previous studies have reported that aerobic exercise is of major importance for type 2 diabetes prevention.
"But many people have difficulty engaging in or adhering to aerobic exercise. These new results suggest that weight training, to a large extent, can serve as an alternative to aerobic exercise for type 2 diabetes prevention."
The participants were asked to fill in questionnaires every two years on their lifestyle and other factors such as television viewing, alcohol consumption, other exercise and family history of diabetes were taken into account.
The researchers found men who did between 1 and 59 minutes of weight training per week reduced their risk of type 2 diabetes by 12 per cent compared with those who did none.
For those completing between 60 and 149 minutes their risk was cut by a quarter and those doing the most, at least 150 minutes reduced their risk by a third.
Aerobic exercise, such as running, had a similar effect with reductions of seven per cent, 31 per cent and 52 per cent respectively.
However men who did more than 150 minutes of aerobics as well as at least 150 minutes of weight training per week had a 59 per cent reduced risk of type 2 diabetes compared to those who did nothing.
Senior author Frank Hu, professor of nutrition and epidemiology at Harvard School of Public Health said: "This study provides clear evidence that weight training has beneficial effects on diabetes risk over and above aerobic exercise, which are likely to be mediated through increased muscle mass and improved insulin sensitivity.
"To achieve the best results for diabetes prevention, resistance training can be incorporated with aerobic exercise."
Another study in the same journal found that people who already have type 2 diabetes can substantially reduce their risk of dying early from the complications caused by the disease, if they exercise.
Dr Diewertje Sluik, of the German Institute of Human Nutrition Potsdam-Rehbrücke, in Nuthetal, Germany, studied 5,859 patients with diabetes and examined 12 other studies.
Those who were moderately active cut their risk of dying from heart disease by around half and from any cause by around 38 per cent.
Moderate activity was defined as people who had a sedentary job but cycled, walked in leisure time or those with a job that involved standing for most of the time.
In an accompanying editorial Dr Mitchell H. Katz, of the Los Angeles County Department of Health Services, said the effect of exercise on mortality was greater than could be expected from drugs.
By Rebecca Smith