The assessment of weight loss from a single measurement of body weight: the problems and limitations

Abstract

Estimation of weight loss plays a key role in the nutritional assessment of patients. The loss is usually calculated by subtracting the patient's observed weight (O) either from his recalled weight (R) or from his predicted weight (P) taken from standard tables or equations. We have compared these two assessments of weight loss (R-O, P-O) in a cross-sectional study of patients in the surgical wards of a teaching hospital. There are large differences (up to 15 kg) between average predicted weights taken from the various published tables. We have obtained predicted weights using equations derived from a healthy local population. We have devised a general technique with which the measured, R and P weights in a group can be used to give random errors of R, P, and true weight loss. In our patients there were 3.6, 10.7, and 6.0 kg respectively. As the random error of R was smaller than that of P in our patients, R-O gave better estimates of the mean and SD of the weight losses of the group of patients than did P-O, and R-O was a more precise estimate of the true weight loss of an individual. Nevertheless, R-O is only an estimate of the true weight loss and had a large random error (up to 7.2 kg). This error which can be calculated for any group of patients, must be borne in mind when using R-O to estimate the weight loss in an individual, and when selecting patients with a given weight loss. In 100 patients such as ours, 24 would have R-O greater than 10 kg, but only 18 of these would have lost 10 kg, and nine other patients who had lost 10 kg would be missed.

Nutritional status of HIV-seropositive subjects in an AIDS clinic in Paris

“…The initial nutritional classi®cation was based on weight loss, a criterion commonly used in previous studies (Morgan et al, 1980;O'Sullivan et al, 1985;Ysseldyke, 1991). Although differences in sampling methods make comparisons with previously published studies dif®cult, the prevalence rate of malnutrition was relatively low in the subgroup of AIDS patients (61.8%).…”

“…According to the usual criteria (Morgan et al, 1980;O'Sullivan et al, 1985;Ysseldyke, 1991), patients were categorised into four classes according to the percentage of body weight loss (BWL), calculated by reference to the usual body weight (UBW), as follows:…”

Nutritional status of adult inpatients in Bujumbura, Burundi (impact of HIV infection)

“…According to the usual criteria (Morgan et al, 1980;Ysseldyke, 1991;Niyongabo et al, 1997), patients were categorised into three classes on the basis of the percentage of body weight loss (BWL), calculated by reference to the usual body weight (UBW), as follows: (i)BWL 10% (no malnutrition) (ii) 10%`BWL 20% (moderate malnutrition) (iii)BWL b 20% (severe malnutrition).…”

Nutrition in multiple sclerosis

“…The most common anthropometric measurement is body weight (50). Recent weight loss is a very sensitive marker of a patient's nutritional status and should be measured very frequently (51). Weight loss of more than 5% in 1 month or 10% in 6 months before hospitalization has been shown to be clinically significant (52).…”