Boston, MA – Men who do weight training regularly—for example, for 30 minutes per day, five days per week—may be able to reduce their risk of type 2 diabetes by up to 34%, according to a new study by Harvard School of Public Health (HSPH) and University of Southern Denmark researchers. And if they combine weight training and aerobic exercise, such as brisk walking or running, they may be able to reduce their risk even further—up to 59%.

This is the first study to examine the role of weight training in the prevention of type 2 diabetes. The results suggest that, because weight training appears to confer significant benefits independent of aerobic exercise, it can be a valuable alternative for people who have difficulty with the latter.  

The study will be published online in Archives of Internal Medicine on August 6, 2012. 

“Until now, previous studies have reported that aerobic exercise is of major importance for type 2 diabetes prevention,” said 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. “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.” 

Type 2 diabetes is a major public health concern and it’s on the rise. An estimated 346 million people worldwide have type 2 diabetes, and diabetes-related deaths are expected to double between 2005 and 2030, according to the World Health Organization. More than 80% of these deaths occur in low- and middle-income countries. 

The researchers, including senior author Frank Hu, professor of nutrition and epidemiology at HSPH, followed 32,002 men from the Health Professionals Follow-up Study from 1990 to 2008. Information on how much time the men spent each week on weight training and aerobic exercise came from questionnaires they filled out every two years. The researchers adjusted for other types of physical activity, television viewing, alcohol and coffee intake, smoking, ethnicity, family history of diabetes, and a number of dietary factors. During the study period, there were 2,278 new cases of diabetes among the men followed. 

The findings showed that even a modest amount of weight training may help reduce type 2 diabetes risk. The researchers categorized the men according to how much weight training they did per week—between 1 and 59 minutes, between 60 and 149 minutes, and at least 150 minutes—and found that the training reduced their type 2 diabetes risk by 12%, 25%, and 34%, respectively, compared with no weight training. Aerobic exercise is associated with significant benefits as well, the researchers found—it reduced the risk of type 2 diabetes by 7%, 31%, and 52%, respectively, for the three categories above. 

The researchers also found that the combination of weight training and aerobic exercise confers the greatest benefits: Men who did more than 150 minutes of aerobics as well as at least 150 minutes of weight training per week had a 59% reduced risk of type 2 diabetes. 

Grøntved said that further research is needed to confirm the results of the study as well as to analyze whether or not the findings can be generalized to women. 

“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,” said Hu. “To achieve the best results for diabetes prevention, resistance training can be incorporated with aerobic exercise.” 

Other HSPH authors included Eric Rimm, associate professor in the Departments of Epidemiology and Nutrition, and Walter Willett, Frederick John Stare Professor of Epidemiology and Nutrition and chair of the Department of Nutrition. 

Support for the study was provided by the National Institutes of Health (DK58845 and CA55075). 

“A Prospective Study of Weight Training and Risk of Type 2 Diabetes Mellitus in Men,” Anders Grøntved, Eric B. Rimm, Walter C. Willett, Lars B. Andersen, Frank B. Hu, Archives of Internal Medicine, online August 6, 2012.

Disability - fibre and constipation

Some people with disabilities suffer from constipation. Contributing factors can include the medications that they may take, low levels of physical activity, insufficient fluids and a diet that may be too low in fibre. Increasing the amount of fibre in the diet not only treats constipation but also lowers cholesterol, may reduce the risk of various cancers and bowel diseases, and improves general health and well-being

Two main types of fibre
The two broad categories of fibre include:

• Soluble fibre - softens the faeces by absorbing water and helps slow the rate of digestion and lower blood cholesterol and blood glucose. It is found in a range of foods including legumes, fruits, vegetables and oat bran

• Insoluble fibre - helps prevent constipation and other associated disorders, such as haemorrhoids, by adding bulk to the faeces and making the food products pass more quickly through the bowel. It is found in a range of foods including wheat bran and wholegrain cereals and breads.

Fibre keeps the digestive system healthy
Fibre:

• Encourages the passage of food and wastes through the digestive system (peristalsis).

• Reduces the risk of bowel diseases such as chronic constipation, diverticulitis and irritable bowel syndrome.

• May reduce the risk of various cancers, particularly those of the bowel.

Fluid is also important
Fibre can only help to relieve constipation if there is enough fluid in the diet for it to be able to do its work. Fibre absorbs water to produce a soft and bulky stool. Everyone should drink at least 2 litres of water each day, particularly in hot weather. Some people with a disability may need to be reminded to drink regularly. Water is the best drink.

Inactivity can cause constipation
Some people with a disability have conditions that affect their mobility, and this can also be a reason why a person is constipated. A person with a disability needs to be as active as possible each day, as every little bit of regular exercise helps.

Fibre can help with other health problems
A diet rich in fibre can help in many ways, including:

• Weight management - obesity increases the risk of a range of health problems, including diabetes and heart disease. Fibre is key to healthy weight management. Since it is indigestible, it provides a sensation of fullness without the kilojoules.

• Atherosclerosis - high blood cholesterol is a contributing factor in the development of atherosclerosis (narrowing of the arteries), which can cause a range of health problems including high blood pressure and heart disease. Soluble fibre (such as legumes, fruits and vegetables) helps to reduce blood cholesterol.

• Diabetes - a diet high in soluble fibre is digested and absorbed more slowly, which leads to lower blood glucose levels.

How much fibre?
Dietitians generally recommend about 30g of fibre every day. Packaged foods such as breads and cereals include nutrition information labels, which can help you to calculate your fibre intake, and nutrition books often include fibre charts. A dietitian can provide information to individuals on the type and quantities of foods that need to be eaten to achieve 30g of daily fibre in the diet each day. Examples of the fibre content in some foods include:

• Four slices of wholemeal bread - about 7g

• Half a cup of baked beans - about 7g

• Two medium pieces of fruit - about 6g.

General cautions
Changes to eating habits should be made with some care. For example:

• A sudden increase in dietary fibre can upset the digestive system and cause symptoms including flatulence (gas) and abdominal pain. It is better to slowly increase the amount of fibre in the diet over a period of several weeks.

• Diets that are too high in fibre can hinder the absorption of certain minerals including iron, zinc and calcium. Avoid consuming more than 35g of fibre per day.

• Do not use fibre supplements unless you have checked with your doctor or dietitian, since these products can aggravate or cause constipation, particularly if you don’t drink enough fluids. Some people with a disability have swallowing problems. Many fibre supplements thicken when added to fluid and this may cause a person with swallowing problems to choke.

• It is important to drink sufficient fluids. It may be helpful to always include a glass of water at each meal or snack.

Things to remember

• Some people with a disability suffer from constipation.

• Contributing factors can include medications, low levels of physical activity, insufficient fluids and a diet that is low in fibre.

• Dietitians generally recommend about 30g of fibre every day.