Why Youth Pre-Diabetes May Be Rapidly Rising Even If Obesity Isn't

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"I don't get it," was my reaction to today's major report on the dramatic rise in "prediabetes" and Type 2 diabetes among America's youth over the last decade-plus. "The diabetes rate is more than doubling even as the youth obesity rate is hitting a plateau? But isn't Type 2 diabetes linked to obesity? So how can one be rising so rapidly while the other flattens out?"

[module align="right" width="half" type="pull-quote"]'This age group with Type 2 diabetes may lose approximately 15 years of their remaining life expectancy.'[/module]

I turned to Dr. Erinn Rhodes, director of the Type 2 Diabetes program at Boston Children's Hospital. But before we get to her analysis, I asked her to explain what "pre-diabetes" is, as she would to one of her patients.

"Usually," she said, "the way I describe it is that the pancreas has been working to try to keep up with the body’s ability to keep its blood sugar in the normal range, but it’s been working so hard that it’s no longer able to do that. And consequently the blood sugar has started to climb into a slightly abnormal range."

Dr. Erinn Rhodes
Dr. Erinn Rhodes

The natural history of pre-diabetes is still being studied, she said; some proportion of children who have it do go on to full-fledged Type 2 diabetes, and some revert into the normal blood-sugar range. Still, it is a clear warning sign.

So how, I asked, could it be rising so quickly -- from 9 percent in 1999 to 23 percent in 2008, according to the journal Pediatrics — if obesity isn't?

Her response:

I think that's an important question and I think the way I would begin to try to understand that is possibly that the Body Mass Index, which is the way they evaluated changes in overweight and obesity over time, probably only tells part of the story when it comes to diabetes and pre-diabetes risk.

Obesity is an important risk factor for pre-diabetes and Type 2 diabetes, but it’s not the only one. We have seen, both in this study and others, that even children with a Body Mass Index in the normal weight category still have a substantial prevalence of pre-diabetes. To try to understand what that's about, you have to start looking at what some of the other risks factors in diabetes and pre-diabetes are, and whether or not there have been changes in those over time.

Gestational diabetes? Low-fat diets? Waist circumference?

There are other genetic and environmental risk factors. For example, gestational diabetes and exposure to gestational diabetes is an early life pre-disposing risk factor for Type 2 diabetes and pre-diabetes, and we've seen a rise in gestational diabetes.

Also, if you think about some of the dietary changes: Even low-fat diets, which may have been prevalent over this time period, may be diets that are high in refined carbohydrates, and those have been shown to lead to higher blood sugar levels and possibly increased risks for diabetes. These are all speculations, and things we may need to look into.

In addition. BMI is only one way of looking at body "fatness" or adiposity. There may be other measures, like waist circumference or waist-height ratio, that may have changed over time and increased, that may be describing different metabolic risks.

These very worrisome trends needs to guide us to start looking more closely at what these numbers mean.

I'd been hoping that maybe the definition of pre-diabetes had changed, and lowering the threshold had suddenly added a huge contingent of kids. But no, Dr. Rhodes said; true, the official threshold for pre-diabetes had dropped from a blood sugar score of 110 to 100, but the Pediatrics study used a constant definition across time, so the rise is real.

How worried should we be about pre-diabetes, I asked, compared to obesity?

Prediabetes is a significant complication of obesity, she said, and when left unchecked, certainly raises the risk of going on to develop Type 2 diabetes, especially if you have additional risk factors.

"So I think all of these are just indicators that we have a lot of work to do to really understand how we're going to turn these important and highly worrisome trends around for children," she said. "I don't think it guides us yet to exactly where and how to best direct our efforts, but it guides us to the importance of the need to look at all these issues much more closely. These are adolescents who may potentially be diagnosed with Type 2 diabetes in adolescence. We recently did some modeling studies that suggested that this age group with Type 2 diabetes may lose approximately 15 years of their remaining life expectancy."

This program aired on May 21, 2012. The audio for this program is not available.

Carey Goldberg Twitter Editor, CommonHealth
Carey Goldberg is the editor of WBUR's CommonHealth section.