How To Prevent Type 2 Diabetes

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In type 2 diabetes, elevated blood glucose levels occur in the setting of insulin resistance and a relative reduction in the production of insulin. People with type 2 diabetes have a greatly increased risk of heart attacks, strokes, kidney disease, blindness, neuropathy, and peripheral vascular disease. Up to 70% of patients with type 2 diabetes die prematurely from heart or vascular problems.

In recent years, the prevalence of type 2 diabetes has been climbing.

Classically type 2 diabetes has been a disease of middle-aged and older people, but now it is commonly seen in adolescents and young adults. This increase in type 2 diabetes is related to the obesity and sedentary lifestyles which have become common in Western cultures over the past decades.

However, just as type 2 diabetes can be caused by lifestyle choices, it can also be prevented, to a large extent, by lifestyle choices.

What Causes Type 2 Diabetes?

Type 2 diabetes has a strong genetic component. People with close relatives with type 2 diabetes, as well as people of Asian, Hispanic, African American or Native American origin, have an increased genetic risk. However, even in people with a strong genetic risk, developing diabetes is not inevitable. In many people, diabetes develops only when suboptimal lifestyle choices are superimposed on the genetic risk.

At least two large observational studies have now concluded that type 2 diabetes strongly associated with lifestyle choices:

  • In a population of 85,000 female nurses followed for 16 years, the 3,300 nurses who developed type 2 diabetes were significantly more obese, more sedentary, ate poorer diets, and were more likely to smoke than the nurses who did not develop diabetes. The investigators estimated that nearly 90% of the type 2 diabetes in this population was related to lifestyle choices.
  • In the National Institutes of Health--AARP Diet and Health Study, a population of nearly 115,000 men and 92,000 women were followed for 10 years, and about 10% of the men and 8% of the women developed type 2 diabetes. Type 2 diabetes was strongly associated with those same risk factors (weight, diet, activity and smoking). Taken together, 80% of the diabetes appearing in these patients could be accounted for by one or more of these risk factors. However, being overweight produced the highest risk, and the investigators estimated that having a normal weight, by itself, reduced the risk of developing type 2 diabetes by 60 or 70%.

It is apparent that, for many people at risk, type 2 diabetes can be prevented, or at least significantly delayed.

Preventing Type 2 Diabetes - Lifestyle Modification

Studies have shown that type 2 diabetes can be prevented or delayed with weight loss, diet modification, and exercise.

Two randomized clinical trials - the Finnish Diabetes Prevention Study and the Diabetes Prevention Program - have shown that patients at high risk for diabetes enrolled in a weight loss and exercise program had a significantly reduced risk of developing diabetes.

Because smokers have an increased risk of type 2 diabetes, and because the combination of diabetes and smoking is especially deadly, smoking cessation is also strongly recommended for patients at risk for type 2 diabetes.

Preventing Type 2 Diabetes - Medications

Several oral hypoglycemic drugs have been studied to see if they can reduce the risk of type 2 diabetes in high-risk patients. Metformin and the thiazolidinediones have been demonstrated to be effective. Long-term studies with metformin have shown reasonable safety as well. Long term studies to prevent diabetes with thiazolidinediones have not been conducted, and these drugs are generally not used for this purpose.

While metformin is effective - especially in young patients with obesity or in women who have had gestational diabetes - it is not as effective as lifestyle changes in preventing type 2 diabetes.

Bottom Line

The American Diabetes Association (ADA) recommends intervention for patients at increased risk of type 2 diabetes, in particular, those at risk who have mildly elevated fasting glucose or hemoglobin A1C levels. The recommended intervention is lifestyle change, specifically, weight loss (5 - 10% of body weight), exercise (30 minutes per day of moderate intensity exercise), and smoking cessation.

For patients at high risk who are under the age of 60, or who have a BMI of 35 kg/m2 or more, or who have had gestational diabetes, the ADA recommends that metformin be strongly considered in addition to lifestyle changes.

The bottom line is this: Type 2 diabetes is a very serious condition that often takes a decade or more away from your life -- and the years that you do have are often much more miserable than they ought to be. So if you can prevent type 2 diabetes, you should try. Talk to your doctor about a prevention program specific to your own needs.


Hu FB, Manson JE, Stampfer MJ, et al. Diet, Lifestyle, and the Risk of Type 2 Diabetes Mellitus in Women. N Engl J Med 2001; September 13, 2001 345:790-797.

Reis JP, Loria CM, Sorlie PD, et al. Lifestyle Factors and Risk for New-Onset Diabetes - A Population-Based Cohort Study. Ann Intern Med September 6, 2011 155:I-30.

Tuomilehto J, Lindström J, Eriksson JG, et al. Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med 2001; 344:1343.

Knowler WC, Barrett-Connor E, Fowler SE, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002; 346:393.

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