Lifestyle modifications involving diet and exercise are effective in reducing the incidence of type 2 diabetes (1–3). In particular, lifestyle changes targeted toward increasing daily energy expenditure are a cornerstone treatment of type 2 diabetes (2). In the Diabetes Prevention Research Group study (4), a goal of 150 min/week of physical activity was recommended, and 74% of the patients in this study group achieved this level by 24 weeks. This type of success in exercise modification is made possible in research protocols by intensive individual counseling (5), which may not be easily reproduced in primary care settings. Because of the critical importance of increasing daily energy expenditure and its central role in preventing and/or treating diabetes, one can surmise that instrumentation providing accurate and simple feedback to type 2 patients may have clinical utility.
Therefore, we provide preliminary data on the accuracy of the HealthWear Armband (Roche Diagnostics, Indianapolis, IN), an instrument designed to assess total daily energy expenditure in free-living adults, including those with diabetes, versus the doubly labeled water (DLW) technique. The development of the DLW methodology provides a gold standard from which the accuracy of other devices to measure daily energy expenditure can be determined (6). The DLW method requires little subject cooperation, is unobtrusive, and accurately determines daily energy expenditure throughout a person’s daily routine. Unfortunately, the relatively high price of the oxygen-18 water, the need for mass spectrometer instrumentation, and the high level of technical expertise required has limited its widespread application in clinical research. The HealthWear Armband evaluates daily energy expenditure based on a proprietary algorithm. That is, it uses a collection of sensors to gather information such as movement, heat flow, skin temperature, near-body temperature, and galvanic skin response in conjunction with body measurements such as sex, age, height, and weight to calculate energy expenditure. The heat flow sensor uses sensitive thermocouple arrays and measures the heat dissipated by the body. It is placed between the skin and the side of the Armband exposed to the environment. If such a practical tool was available and validated, it would help the patient monitor or increase their daily energy expenditure levels to lose weight with the ultimate goal of reducing the complications of diabetes.
As part of a larger study, we assessed total daily energy expenditure in six diabetic patients treated with diet only and/or oral hypoglycemic agents. We tested two men and four women, aged 56.5 ± 5.96 years with a BMI of 29.76 ± 4.12 kg/m2, a fat-free mass of 50.08 ± 12.17 kg, and a fat mass of 31.98 ± 6.99 kg (determined by dual-energy X-ray absorptiometry). All subjects wore the HealthWear Armband simultaneously with the determination of DLW during a 10-day period to measure total daily energy expenditure. The armband was worn around the right arm and was removed only for showering and bathing purposes. “On body time” for the armband was 99% during the 10-day period for all subjects.
In the six diabetic patients, we noted no significant differences (Δ 78.3 ± 158 kcal/day [mean ± SD], 95% CI −87 to 245 kcal/day) in mean daily energy expenditure between the armband (2.237 ± 568 kcal/day) and DLW (2,315 ± 625 kcal/day). Also, the correlation between the armband and DLW reached r = 0.9696 (P = 0.0014). In addition, the intraclass correlation coefficient (ICC) between the armband and DLW reached ICC = 0.9625, with a technical error of measurement of 104 kcal/day. Fourth, individual comparisons between DLW and the HealthWear Armband were examined using a Bland-Altman plot (Fig. 1). The Bland-Altman plot shows the difference in daily energy expenditure between DLW and the HealthWear Armband versus mean daily energy expenditure determined between DLW and the HealthWear Armband. From these data, limits of agreement between DLW and the HealthWear Armband were calculated (i.e., mean difference between DLW and the HealthWear Armband ±1.96 SD of the difference). We hypothesized a narrow limit of agreement (i.e., ± 100–300 kcal/day) between HealthWear Armband and DLW. The measured range of under- and overestimation of the armband versus DLW was −243 to 176 kcal/day, respectively, suggesting an acceptable level of concordance between the two methods.
Although these results will need to be confirmed in a larger sample size, preliminary analyses suggest that the HealthWear Armband is an acceptable device to accurately measure total daily energy expenditure in type 2 diabetic patients over a 10-day period. This information would be useful in counseling patients regarding appropriate levels of daily energy expenditure needed to prevent or offset diabetes and its related complications.
References
R.R.-L. has received honoraria and funds from Roche Diagnostics.
