近年來，許多研究證實，肥胖（obesity）是在老年人口中盛行率很高的慢性疾病之重要危險因子。然而，較少研究探討肥胖或過重對於老人失能的影響。在老年人口中，失能比慢性病盛行率更能反映出老年人口的照護負擔。因此我們利用具全國代表性之貫時性資料，探討肥胖或體重過重對後來發生功能限制（functionallimitations）之影響。資料取自「台灣中老年的健康與生活狀況調查（N=4440）」，其中有1817人，在1999年是完全沒有「力量（strength）」之功能限制，有2302人是沒有「上肢（upper-body mobility）」功能限制，有1984人沒有「下肢（lower-bodymobility）」功能限制。我們利用邏輯迴歸模型，分別探討老人之身體質量指數（BodyMass Index, BMI）是否可以預測這三組老人在2003年各種功能限制的發生情形？結果發現，原來沒有身體力量（strength）之功能限制者有40.95%發展出了力量上之功能限制，而發生上肢與下肢功能限制分別為30.10％和36.09％。而體重過重及體重過輕的老年人，在四年之間，都比體重正常之老年人更容易發生功能限制。但是，BMI與功能限制之間的相關，在控制其它與健康相關之變項後就變成不顯著。本研究結果發現，過重或過輕的身體質量指數（BMI）會增加老年人身體功能限制的發生情形，但BMI對老人身體功能的影響是因為，非正常體位的老年人通常也比較容易發展出許多容易導致失能之慢性疾病。

Over past decades, numerous studies have confirmed that obesity is an important risk factor for many chronic diseases, which are commonly seen among older populations. However, fewer studies have examined the effect of excessive weight on the onset of disability, which is a more relevant measure to reflect the care burden of our frail elderly populations. Using a national representative sample of the elderly in Taiwan, who were free of any functional limitations (FLs) at baseline, this study was to examine if an abnormal body weight is associated with the onset of FLs 4 years later. Data were taken from the fourth wave of the Survey of Health and Living Status of the Middle Aged and Elderly in Taiwan. There were 4440 cases aged 54 and over were interviewed and, among them, 1817 cases were free in their strength FLs, 2302 cases were free of upper-body FLs, and 1984 cases were free of lower-body FLs in 1999. Three separate analyses were conducted for each of the 3 sub-samples of elders. A set of predictors, along with body weight status, were entered hierarchically into logistic regression models to predict the onset of FLs in 2003. Results showed that the incidence rate of developing strength FLs over the 4 year-period was 40.95% and the incidence rates for developing an upper-body and lower-body FLs were 30.10% and 36.09%, respectively. Elders with either an overweight or underweight were more likely to develop a FL 4 years later. However, the significance of an abnormal weight status disappeared after other covariates were taken into account. Based on our findings, it seems that an abnormal weight status does increase the elders' risk of developing FLs; however, this effect can be explained away by other controlled variables, such as socioeconomic status, chronic disease, and health status.