Compared with type 1 diabetes, type 2 is far more common, accounting for 90 to 95 percent of all cases of diabetes. It’s also far more complex.
High blood sugar is still the basic problem. But with type 2, the pancreas doesn’t completely shut off insulin production. Instead, the body’s use of insulin becomes impaired in any number of different ways:
- The beta cells of the pancreas are able to produce plenty of insulin, but they take their sweet time releasing it in response to the surge of glucose that follows a meal. Result: By the time the pancreas puts out the large amounts of insulin the body is waiting for, glucose levels have already built up in the blood.
- The number of beta cells is lower than normal, so the pancreas has trouble keeping up with insulin demand.
- There’s plenty of glucose and insulin, but cells don’t allow insulin to do its job — a condition known as insulin resistance. The problem can be caused by any number of things: A lack of proteins called insulin receptors on cells (think of insulin as a key and the receptor as a lock), a mismatch of insulin and receptors (the keys don’t fit the locks), or flaws in the chemistry that lets insulin pass into the cells. No matter what the problem, the result is the same: Glucose can’t get where it needs to go and stays in the bloodstream instead.
- Excess body weight boosts the need for insulin and the pancreas can’t keep up with demand.
Often, type 2 diabetes results from a combination of these factors, which tend to be interrelated. For example, obesity both creates more demand for insulin and promotes insulin resistance.
The major symptoms of type 2 diabetes mirror those of type 1, but type 2 is different in other ways:
It takes time. Unlike type 1, type 2 develops slowly over time, and symptoms don’t show up right away. When you finally notice that something’s wrong, you may already have had diabetes for years. That can make type 2 diabetes seem a bit vague — if it appears so gradually, when does it actually begin? And once you’re diagnosed, do you really, truly have it? Doctors admit that it’s sometimes tough to say exactly when any given case of diabetes got started — especially after the fact. But exact criteria based on blood-sugar levels clearly define when you have diabetes and when you don’t. Once you have it, you can control it to a remarkable degree, but it never goes away. There is no such thing as “a touch of” diabetes.
Adults suffer most. Type 2 diabetes is sometimes called adult-onset diabetes because it usually strikes after age 40 and is more likely to develop as you get older. One reason: Insulin resistance increases with age. In fact, more than 10 percent of people over age 60 have type 2 diabetes. But, as with other terms for diabetes, “adult onset” is becoming a misnomer because of the increasing prevalence of type 2 in kids.
Blood sugar is more stable. Because the pancreas still produces and releases at least some insulin when it’s needed, glucose levels in the blood don’t tend to swing as wildly as they do with type 1 — even though, on average, unmanaged blood-sugar levels with type 2 are still too high.
The causes of type 2 diabetes have much more to do with lifestyle issues, particularly obesity. But weight doesn’t tell the whole story. In fact, it’s unlikely that type 2 develops because of any one thing. Instead, a number of factors appear to come together, potentially even magnifying each other, with unhealthy results. Among the factors that may come into play:
Genetics. Patterns in twins indicate how strong the genetic link is — and it’s much stronger with type 2 than with type 1. In the case of type 2, if one identical twin has diabetes, the chances of the other getting it are as high as 75 percent. If one parent has type 2, there’s a 20 to 30 percent chance the kids will develop it, too. (If both parents have type 2, the risk to children is about the same as that shared by identical twins.) This makes type 2 a serious concern for ethnic groups that seem predisposed to it — and those groups are not the same ones that are most susceptible to type 1. Whites are most likely to get type 1, but type 2 is more prevalent amoung African Americans, Latinos, Native Americans, Pacific Islanders, and Asian Americans.
Inactivity. Physical activity improves the body’s use of insulin. This happens for a variety of reasons. Muscle, for example, uses glucose more efficiently than other types of tissue, and exercise builds muscle. Unfortunately, the opposite is also true: Lack of physical activity makes cells more prone to insulin resistance. It also contributes to weight gain.
Poor diet. How much you eat matters. But what you eat is also important. And the fat-laden foods so common in the American diet are more likely to pack on pounds than comparable amounts of other, leaner foods.
Age. Type 2 diabetes becomes more common with age, in part because cells in older bodies tend to be more insulin resistant. But it’s also true that people tend to become more sedentary with age. Their metabolism slows down, yet they eat just as much — or more. All of those elements are a prescription for an increased risk of diabetes.