Research
Validation of several established equations for resting metabolic rate in obese and nonobese people

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Abstract

Objective

To evaluate several equations for predicting resting metabolic rate against measured values in obese and nonobese people.

Design

Resting metabolic rate was measured with indirect calorimetry. Four calculation standards using various combinations of weight, height, and age were used to predict resting metabolic rate: a) Harris-Benedict equation, b) Harris-Benedict equation using adjusted body weight in obese individuals, c) Owen, and d) Mifflin. Main outcome was percentage of subjects whose calculated metabolic rate was outside a ±10% limit from measured values.

Subjects/setting

130 nonhospitalized adult volunteers grouped by degree of obesity (range of body mass index, 18.8 to 96.8).

Statistical analysis performed

Analysis of proportions was used to determine differences in the percentage of subjects estimated accurately by each equation; α was set at 0.05.

Results

Calculated resting metabolic rate was more than 10% different from measured in 22% of subjects using the Mifflin equation, 33% using the Harris-Benedict equation (P=.05 vs Mifflin), and 35% using the Owen equation (P<.05 vs Mifflin). The error rate using Harris-Benedict with adjusted weight in obesity was 74% (vs 36% in obese subjects using actual weight in the standard Harris-Benedict equation).

Applications/conclusion

Of the calculation standards tested, the Mifflin standard provided an accurate estimate of actual resting metabolic rate in the largest percentage of nonobese and obese individuals and therefore deserves consideration as the standard for calculating resting metabolic rate in obese and nonobese adults. Use of adjusted body weight in the Harris-Benedict equation led to less overestimation by that equation in obese people at the expense of increased incidence of underestimation.

Section snippets

Methods

This research was conducted at a university medical center. Penn State Milton S. Hershey Medical Center’s Human Volunteer Subject Protection Office approved the protocol for the current study, and written informed consent was obtained from each subject. Subjects were recruited by posting flyers in various locations in the hospital and medical school. Additionally, some subjects were referred from a weight-management clinic and from a surgery clinic that evaluates morbidly obese individuals for

Results

A total of 130 subjects were studied (54 men, 76 women). Characteristics of the sample are shown in Table 1, subdivided by degree of obesity. The groups were evenly matched for height and age. BMI was normally distributed within the obesity groupings, but skewed toward a high BMI in the overall sample. BMI was more than 30 in 36% of subjects, with 57% of these having a BMI more than 40.

Fifty-six percent of the subjects had sedentary lifestyles. The 44% of subjects who were not sedentary

Discussion

Calculation standards for resting metabolic rate have been sought for about 100 years. During that time, many predictive equations for resting metabolic rate have been published 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Among the oldest of these equations are those developed by Harris and Benedict, which have endured even though some have questioned their technological reliability and their physiologic applicability to a population that has become more sedentary, obese, and racially diverse since the

Applications

■ Of the calculation standards tested, the Mifflin standard provided an accurate estimate of actual resting metabolic rate in the largest percentage of nonobese and obese people, with a low rate of overestimation. Among morbidly obese people whose resting metabolic rate was not accurately predicted, the magnitude of error was smaller for the Mifflin equation than for the other equations. For these reasons, the Mifflin equation deserves consideration as the standard for calculation of resting

D. C. Frankenfield is chief clinical dietitian, Department of Clinical Nutrition, Milton S. Hershey Medical Center, Hershey, PA.

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D. C. Frankenfield is chief clinical dietitian, Department of Clinical Nutrition, Milton S. Hershey Medical Center, Hershey, PA.

A. Rowe is an associate professor of medicine, Division of Gastroenterology, Department of Medicine;

J. S. Smith is a professor of surgery and R. N. Cooney is an associate professor of surgery, Division of Trauma/Surgical Critical Care, Department of Surgery, all at Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, Hershey, PA.

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