5.8 Diabetes

Diabetes Mellitus is a metabolic disease in which the body’s ability to produce or properly respond to insulin is impaired which leads to abnormal regulation of blood glucose. There are two primary types of diabetes: type 1 (insulin dependent diabetes) and type 2 ( non-insulin dependent diabetes).

Type 1 diabetes is the least common form of the disease accounting for approximately 5-10% of all cases of diabetes in the US (13). It is an autoimmune disease where the body’s immune system attacks the insulin producing cells of the pancreas which prevents the body from making insulin. If you recall from earlier in this chapter, insulin is the hormone that stimulates the cells of the body to take in glucose (and other nutrients) from the blood. Without insulin, glucose cannot enter into any cell of the body and it remains in the blood accumulating to very high levels and the cells are then deprived of their main energy source. The reason type 1 diabetes is referred to as insulin dependent diabetes is because the individual with type 1 diabetes has to rely on an outside source of insulin, such as an insulin pump or injection, in order to survive. Type 1 diabetes used to be referred to as “juvenile onset” diabetes because it was more often diagnosed in children and young adults. Although it tends to be diagnosed more often at younger ages, it can occur at any age. Some people are diagnosed with type 1 diabetes for the first time in their 60’s or 70’s.

Type 2 diabetes is far more common  than type 1, accounting for approximately 90-95% of all cases (13). People with type 2 diabetes can produce insulin, they just do not produce enough insulin or the insulin that they produce does not bind properly with the insulin receptors on the cell membranes. This condition is referred to as insulin resistance. As a result, some glucose enters into the cells but not enough and glucose builds up in the bloodstream. A person is generally insulin resistant for a time before they are diagnosed as having diabetes and insulin resistance is sometimes referred to as pre-diabetes. Insulin resistance should be viewed as a disorder on its own, as well as a process leading to diabetes. It indicates that the hormonal system that regulates blood glucose is beginning to work abnormally. The resistance of the cells to insulin gradually worsens over time so less and less glucose is entering the cells and more is remaining in the blood. When blood glucose reaches a certain point, the person is then diagnosed with diabetes. The exact cause of insulin resistance is unknown but may be related to excess amounts of body fat and lack of physical activity. Type 2 diabetes was previously referred to as adult onset diabetes because it was uncommon in children and adolescents. However, the number of children and adolescents diagnosed with type 2 diabetes has grown dramatically and type 2 diabetes is no longer referred to as “adult onset diabetes.”

Prevalence of Diabetes in the U.S.

In the United States the prevalence of diabetes is increasing at an alarming rate. The incidence of diabetes has more than doubled in the last 20 years. As of 2019, it is the 7th leading cause of death in the U.S. and a major risk factor for heart disease and stroke (13). In 2019, 37.3 million Americans had diabetes representing 11.5% of the population, with most cases being type 2 (14). Furthermore, the number of Americans with diabetes continues to grow. It is estimated that nearly ⅓ of American adults suffer from prediabetes or insulin resistance and 80% of those with prediabetes are unaware they have it. If present trends continue, it is estimated that 1 in 3 American adults will have diabetes by 2050. Public health officials are also very concerned about the increasing prevalence of type 2 diabetes among children and adolescents.


One of the primary problems with type 2 diabetes is that it comes on slowly over time and does not cause any dramatic and obvious signs and symptoms which can allow it to go undiagnosed for long periods of time. Of the 37.3 million cases in 2019, 8.5 million were undiagnosed (14). Some individuals with type 2 diabetes experience symptoms such as excessive thirst and excessive urination but many do not. The text box below describes some of the signs and symptoms associated with diabetes according to the CDC (15). Consequently, diabetes can silently damage many organs and systems in the body and cause serious health complications without the person being aware of it. Over time, constant exposure to high blood glucose damages nerves, blood vessels and organs. Poorly controlled or undiagnosed diabetes are a major cause of heart attack, stroke, kidney failure, blindness and lower limb amputations. The majority of non-traumatic lower-limb amputations among people aged 20 years or older occur in people with diagnosed diabetes.

Signs and symptoms of diabetes (15)

  • Elevated blood glucose
  • Excessive thirst
  • Frequent urination
  • Blurred vision or sudden visual changes
  • Foot pain
  • Numbness in extremities
  • Impotence (men)
  • Wounds that do not heal (especially on the lower extremities)
  • Increased appetite with rapid weight loss
  • Breath or urine that smells like fruit

Who Is at Risk and Can It Be Prevented?

Diabetes has reached epidemic proportions over the last 30 years and rates continue to increase. Certain people are at greater risk for developing type 2 diabetes (16). As with all chronic diseases, some risk factors are controllable and some are not.

Table 5.4 Risk Factors for Type 2 Diabetes (16)

Non-modifiable Risk Factors Modifiable Risk Factors
Family history – Your risk increases if a parent or a sibling has type 2 diabetes. Excess body fat – The more fatty tissue you have, the more resistant your cells become to insulin. Excess fat stored in the abdominal cavity increases your risk of diabetes more than body fat stored in other areas of the body.
Age – Your risk increases as you get older. This may be related to loss of muscle mass and weight gain frequently associated with increasing age. Generally, type 2 diabetes occurs in middle-aged adults, most frequently after age 45. But type 2 diabetes is increasing dramatically among children, adolescents and younger adults. Inactivity – Physical activity helps you control your weight, uses up glucose as energy and makes your cells more sensitive to insulin.
Race/Ethnicity – It is unclear as to why, but people of certain races — including African Americans, Hispanics, American Indians and Asian-Americans — are at higher risk.These trends are not necessarily the same worldwide which suggests that these populations are more sensitive to the poor Western diet and lack of physical activity so prevalent in the United States.
History of gestational diabetes – If you developed diabetes during pregnancy or delivered a baby over 9 lbs., you are at increased risk of developing diabetes as you age.

There is no way to prevent type 1 diabetes but type 2 is largely preventable, and in some people, reversible. By reducing body fat, increasing physical activity levels, and eating a healthy diet high in fiber and protein, some people can prevent or delay the onset of diabetes. In a large study of more than 3000 individuals with pre-diabetes it was shown that those who made lifestyle changes, such as the ones mentioned above, and met with a professional for education and support, were 58 percent less likely to develop type 2 diabetes than those who did not (17). The initial study has been expanded to a national program called the Diabetes Prevention Program that is implemented in hospitals and health clinics nationwide to prevent or delay the development of type 2 diabetes.

Figure 5.19 Diabetes Overview

Infographic summarizing signs and symptoms for diabetes


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Nutrition and Physical Fitness Copyright © 2022 by Angela Harter Alger is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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