Gittelsohn J, Shankar A V, Pokhrel R P, West K P
Department of International Health, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, MD 21205.
J Am Diet Assoc. 1994 Nov;94(11):1273-7. doi: 10.1016/0002-8223(94)92459-7.
To determine the accuracy of direct observation in food-weight estimation as measured under controlled field conditions.
Ten local Nepalis were trained in observational techniques and tested in food-weight estimation during a 3-month training period and for 4 months after training.
The study was carried out in the Sarlahi District, a rural, central lowland region of Nepal that borders India.
Thirty testing sessions (a total of 6,902 observations) were completed on more than 150 different foods. Estimates of observed food weight were compared with actual weights and were analyzed.
Pearson's correlation coefficients were calculated to examine associations between estimated and actual weights.
Observer estimates of food weights were highly correlated with actual weights (r = .96) for the entire testing period. The linear regression equation (y = .96x + 1.3) suggests that the relationship between actual and observed food weights (in grams) was also accurate. Most observers showed improvement with training. Substantial reductions in both mean and standard deviation of percentage error were achieved over time. Accuracy of estimates was influenced by characteristics of foods weighted; small quantities (less than 20 g), certain nonstaple foods, and foods of high volume but light weight had less accurate estimates.
Direct observation is an important method for assessing dietary intake that does not rely on a respondents' ability to recall his or her own or another's food consumption. It is feasible to train local observers to make visual estimates of food weight, but the accuracy of their estimates varies by food and portion size.
确定在受控现场条件下测量的直接观察法在食物重量估计中的准确性。
10名当地尼泊尔人接受了观察技术培训，并在为期3个月的培训期间以及培训后的4个月内进行了食物重量估计测试。
该研究在尼泊尔中部低地农村地区与印度接壤的萨拉希区开展。
对150多种不同食物完成了30次测试（共6902次观察）。将观察到的食物重量估计值与实际重量进行比较并分析。
计算皮尔逊相关系数以检验估计重量与实际重量之间的关联。
在整个测试期间，观察者对食物重量的估计值与实际重量高度相关（r = 0.96）。线性回归方程（y = 0.96x + 1.3）表明实际食物重量与观察到的食物重量（以克为单位）之间的关系也是准确的。大多数观察者通过培训有所进步。随着时间的推移，百分比误差的均值和标准差均大幅降低。估计的准确性受所称重食物特征的影响；少量（少于20克）食物、某些非主食类食物以及体积大但重量轻的食物估计准确性较低。
直接观察是评估饮食摄入量的一种重要方法，不依赖受访者回忆自己或他人食物消费情况的能力。培训当地观察者对食物重量进行视觉估计是可行的，但其估计准确性因食物和份量大小而异。
