The Tribune

By Arch Mainous, University of Florida

(THE CONVERSATION) - Type 2 diabetes has reached epidemic proportions, with an estimated 29 million people in the US having the disease and another 86 million considered prediabetic. With an estimated cost of $245 billion, prevention becomes critically important to stem the tide of increasing diabetes prevalence.

Diabetes is a chronic, treatable disease, but there are no cures. Weight loss surgery has been shown to help in some individuals, and medication can help. Identifying individuals at high risk for development of diabetes, adults with prediabetes, and then providing treatment to them is an effective strategy to slow or eliminate its progression.

The prevailing wisdom and screening and treatment recommendations begin with the starting point that adults who are overweight or obese are the ones who are likely to have prediabetes. Weight loss for those individuals is the primary recommended lifestyle intervention. Exercise and eating healthy foods are part of that.

As someone who has studied diabetes, I have discovered recently with colleagues that we may be missing millions of adults with prediabetes. Our screening systems in the US are focusing only on these individuals who are overweight or obese.

Our studies suggest it may not be as simple as classifying people as overweight or obese versus healthy. Our thinking of risk and screening should also consider body composition.

A hidden danger

In an analysis of nationally representative data looking at 18-year trends in prediabetes among healthy weight adults, in 2012, 33 per cent of adults 45 and older at "healthy weight" in the United States had prediabetes, defined as a Haemoglobin A1c of 5.7 per cent to 6.4 per cent. The proportion of adults at healthy weight with prediabetes had shown a significant rise over time. This is particularly troubling because the health care authorities have told this group that they are "healthy," and we are not looking for diabetes in them.

The screening recommendations of the United States Preventive Services Task Force suggests screening for abnormal blood glucose (prediabetes and diabetes) only in adults who are overweight or obese. Based upon these guidelines, millions may be leaving their doctor's offices with an unidentified risk for one of the most debilitating and expensive chronic illnesses in the US.

Moreover, since these adults are what we would consider to be a healthy weight, the usual strategy of calorie restriction and weight loss is called into question as an appropriate prevention strategy.

These findings make us wonder whether we need to shift our thinking about what may predispose one to prediabetes and how to prevent and delay progression to diabetes in this high-risk population.

Instead of looking only at weight, we should think in terms of a healthy body composition represented by the proportion of lean body mass to fat. People at healthy weight but poor body composition that is, someone with low weight but also low muscle mass in proportion to their body fat, what some have termed "skinny fat."

We think a healthy body composition is more important than weight. Body composition refers to the proportion of lean body mass to fat. Over time, that proportion changes, as some muscle loss is inevitable from aging.

We may not be able to see this change in in our bodies or on the scale. A 55-year-old man, for example, who still weighs close to what he weighed at 25 will have a different proportion of lean body mass to fat, with more fat most likely.

Although some lean muscle mass loss is inevitable as we age, exercise can counteract some of the loss. Unfortunately for us, as our industrialised society moves to a sedentary lifestyle, getting that exercise becomes more of a challenge.

Just as society has shifted in our activity levels, we may have to shift our thinking about health. We may be working with a false dichotomy that of overweight and obese versus healthy.

Getting a grip can help

We have conducted several studies that suggest there may be a simple way to screen for lean muscle mass. We can test grip strength, as measured by a hand grip dynamometer, an instrument that measures the strength of hand and forearm muscles. This could be done in a doctor's office in a very non-intrusive way in about 30 seconds.

We found that among individuals at healthy weight, lower grip strength is associated not only with undiagnosed diabetes in adults but also prediabetes. Thus, by focusing on muscle and body composition, we can distinguish individuals in the healthy weight category who have abnormal blood glucose, an indicator of prediabetes or diabetes.

We haven't established the cut-points, or measurements, of grip strength for use in practice with different patient populations (eg, young men, old women, tall men), but that is where we need to go in future studies.

This helps us to rethink not only how we view the illness but also who may be at risk. Further, it also helps us think of potential strategies to deal with this problem.

For example, what are the next steps for individuals who are at a healthy weight? They are already at a suggested healthy weight, but that is providing a misleading assurance of health for many of these adults. To avoid missing these people, should we consider expanding the current Preventive Services Task Force recommendations of screening for abnormal blood glucose to include adults at healthy weight as well as those who are overweight or obese?

It is unclear whether that type of expansion would be cost effective. Would it be better to focus on refining our measures of body composition among individuals at healthy weight to select those at the highest risk?

It is still premature to recommend specific interventions for individuals at healthy weight to prevent diabetes. It may, however, be worthwhile to emphasise resistance exercise in a healthy lifestyle rather than having individuals focus on what the scales say about their weight. Think body composition, not just thin.