What is Diabetes? The Difference Between Type 1 and Type 2

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26 million people in America have it, in one type or another. 79 million have pre-type 2.

But what exactly is Diabetes? There are a lot of myths and misunderstandings surrounding the disease, particularly when it comes to type 1 versus type 2.

So let’s start with the basics. Diabetes is a chronic condition characterized by high blood glucose (sugar), but it’s really all about a hormone called insulin. Depending on the type of diabetes you have, your body either can’t make enough insulin to keep blood sugar levels down (type 1), or can’t effectively use the little insulin that it does produce (type 2).

First, to understand what happens in the bodies of people who have diabetes, you should know what happens in the bodies of people who don’t.

Blood sugar, or glucose, is the body’s main source of energy. This glucose comes from food—mostly carbohydrates, but occasionally from proteins, too.

In a healthy body, carbs are all broken down into glucose.  That glucose leaves the intestine, travels through the liver, and eventually makes its way into the blood stream. Its final destination is the body’s cells, where it is used to create energy.

Insulin comes into play here, at the cells’ entrance. The hormone acts as a doorman, allowing glucose to come inside.

Insulin is produced in the pancreas by little clusters of cells, known as beta cells. Beta cells sense when there is an excess of glucose in the blood stream, such as just after a meal, and they send insulin out to meet the glucose at the cell’s doors.

When working properly, this interplay between glucose, insulin, and beta cells maintains glucose levels between 70 and 140 milligrams per deciliter of blood.

In both types of diabetes, this balance gets interrupted in some way.

In type 1, the body’s immune system starts attacking and destroying parts of itself—specifically, its own beta cells. Fewer beta cells means less insulin secreted into the body. And less insulin means that glucose is locked out of cells, and stays in the blood stream.

As type 1 diabetes progresses, it’s thought that beta cells are completely wiped out (though some early research suggests there may still be some faint activity of beta cells in some people with type 1).

Most people with type 1 diabetes need to start injecting insulin as soon as they are diagnosed. They do need to be careful of what they eat, so to avoid causing spikes in their blood glucose, but type 1 cannot be controlled solely with diet. The necessity for treatment with insulin is why type 1 is classified as insulin-dependent.

In type 2, some insulin is released but the locks on the cells are damaged. Insulin’s keys no longer fit, and the cells refuse to unlock. Because the door isn’t opened, glucose can’t enter, also resulting in heightened blood glucose levels. This is called insulin resistance—since the cells are resistant to the influences of insulin.

Genetics certainly affect susceptibility to insulin resistance, but another major factor is obesity. The greater your BMI, the harder your body has to work to make insulin effective. So it’s no coincidence that the global epidemic of type 2 diabetes coincides with rising rates of obesity.

In early stages, it’s possible to control type 2 with diet and exercise. Losing just 7 to 10 percent of your body weight can make the insulin your body produces more effective; meal planning helps you eat according to the amount of insulin available in your body, and exercise helps to increase insulin sensitivity (though many institutions recommend that patients get help from a medicine like metformin right away).

And for a while the body can overcome the cells’ resistance. But over the course of type 2, particularly when it’s poorly managed, the body stops being able to make enough insulin to force its way into the cells. When this happens, people with type 2 also need to start insulin injections.

Type 1 and type 2 are different in their root causes, but the effects are eventually the same. Problems with insulin interrupt the finely honed system and glucose in the blood rises, which, if left untreated, may result in complications like nerve and eye damage.

These are just the very basics of the two major types of diabetes—there is a lot to know about the disease and its variations. But understanding your body is the first step.

For more information on living with diabetes, visit the Joslin web site.

9 Responses to What is Diabetes? The Difference Between Type 1 and Type 2

  1. wilson cua says:

    the other difference type2 is inheritable while in type 1 is not

    • Dr. Gaglia says:

      While it is true that the majority of people who are diagnosed with type 1 diabetes do not have a known relative with the disease, there is actually a very strong genetic component (it is just that the genes are very common in some populations). It is estimated that relatives of a person with type 1 diabetes have a 10 to 15 times greater risk of developing the disease than someone without a family history.

      Currently it is believed that there is a genetic predisposition, then something happens that is not well understood, perhaps some type of environmental exposure, then autoimmunity against the insulin producing beta cells develops. In some people the immune system is able to be turned off and they never develop clinical disease (but if you looked in their blood they might have autoantibodies directed against the beta cells) in other people, the immune system continues to destroy the beta cells until there isn’t enough insulin around to keep blood sugars in the normal range clinical diabetes develops.

      For more information about studies for persons who may be at risk for developing type 1 diabetes based on family history please check out the Joslin website “Volunteer for Clinical Research” section.

  2. If type 1 is not inheritable, then why does Trial Net determine if the type 1 gene is present in a person’s body? I know families in which there are as many as three type 1 children. That sounds like their type 1 was inheritable. In my own case, I had all the classic symptoms of type 1 while recovering from chicken pox and mumps in 1945, when I was 5 years old. I do not have any relatives with type 1, so I agree my diabetes was not inheritable, but in other cases, it dos seem to be inheritable.

  3. DrBB says:

    @Richard & Wilson: I’ve heard both assertions before and would love to know what the story really is. I’m Type I, from a large family, and the only other case I’m aware of is the daughter of my first cousin. So it doesn’t seem to run in my family at least. But I don’t know how to square that with the info that it’s also a matter of genetic susceptibility to whatever virus triggers the auto-immune response. The article presents the standard account I’ve heard since I was first diagnosed (30 years ago!) but leaves these questions–which someone asks pretty much every time I’VE given the standard account–unaddressed.

  4. Ralph Joslin says:

    In 1934 & 1935 my aunt & uncle died of type 2 diabetes 30 days apart. They were 26 & 27 years old. Since then 16 members of my family have some form of type 2 diabetes. I am in my seventies and have just been diagnosed with type 2. Genetics is a large part of the problem since none of us are overweight.

  5. Scott says:

    Actually type 1 is inheritable, but it still happens because of the immune system attack of the beta cells. It is just higher chance of the beta cell system attack,

  6. Thanks to everyone who commented. Here’s a brief response from Dr. Jason Gaglia, a scientist at Joslin whose research focus is on type 1 diabetes. (Copied from his response to one of the comments above…)

    “While it is true that the majority of people who are diagnosed with type 1 diabetes do not have a known relative with the disease, there is actually a very strong genetic component (it is just that the genes are very common in some populations). It is estimated that relatives of a person with type 1 diabetes have a 10 to 15 times greater risk of developing the disease than someone without a family history.

    Currently it is believed that there is a genetic predisposition, then something happens that is not well understood, perhaps some type of environmental exposure, then autoimmunity against the insulin producing beta cells develops. In some people the immune system is able to be turned off and they never develop clinical disease (but if you looked in their blood they might have autoantibodies directed against the beta cells) in other people, the immune system continues to destroy the beta cells until there isn’t enough insulin around to keep blood sugars in the normal range clinical diabetes develops.

    For more information about studies for persons who may be at risk for developing type 1 diabetes based on family history please check out the Joslin website “Volunteer for Clinical Research” section.”

    –Keep an eye out for an informational video about TrialNet, which explores this question further.

  7. susie smith says:

    i am really tired of the blame game, saying being overweight is why someone gets type 2 diabetes. there is an obvious heredity link, and there are lots of overweight folks who do not have diabetes. ethnic origin is also major factor. in research there is a distinction between correlation and causeation. there may be a correlation with being overweight, but not a causeation. there is also a strong link to being pregnant and causing diabetes. that is why almost 75% of those with gestational diabetes get diabetes within 5 years. and the effect of estrogen: every woman who tests her blood sugar knows there is a spike as high as 100 points each month a week before her period. is that her fault also!. there is so much research to do and info to get out. i just think more should be focused on the disease and less on blaming those overweight for every single disease possible. folks should also know that doing weight and weight resistance training has a much more effective result to lower blood sugar than simple cardio. the ony research on this was done in the netherlands, but trust me, use the weights and test your blood sugar. also, the new drug victoza actually got me off of six years of insulin. please tell the whole story and quit focusing on the blame game.

  8. Type 2 is inheritable , I say this because there are more three people in my family with type 2, so I believe that it is inheritable. Type one is all about the lack of insulin being produced to maitain the sugar (glucose )levels.

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