Evaluation of protocols for assessing energy needs in overweight and obese adults
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Accurate estimation of energy needs in overweight and obese adults is essential for long term weight management and during hospitalization, when in the presence of metabolic stress, significant underfeeding encourages loss of lean tissue. Modification of the Harris-Benedict equation (HBE) published in 1919 and derivation of new equations have attempted to accurately predict energy requirements in overweight/obese individuals. Objectives for this research were to examine protocols for adjusting weight in the HBE and to evaluate more recently developed predictive equations, for accuracy in estimating basal energy expenditure (BEE) of overweight and obese adults. Subjects were 53 overweight/obese and 53 normal weight healthy adults matched for gender, height, and age. Indirect calorimetry and dual energy x-ray absorptiometry were used to assess BEE and body composition, respectively. Study specific (SS) equations to predict BEE for normal and overweight/obese adults were derived using linear multiple regression. A hypothesis that excess fat-free mass (FFM), i.e., FFM above that carried at normal weight, in overweight/obese subjects would provide a tailor-made adjustment for weight in the HBE proved false. Mean excess FFM in our population was 17% while others had observed that adding 25% of the excess weight to standard body weight (SBW) in overweight/obese adults to be inadequate. SS, Owen and Mifflin equations predicted measured BEE (MBEE) within ±10% for about 75% of all normal weight subjects and about 65% of the overweight/obese subjects. Overweight/obese subjects were partitioned into two groups, those >125 to 150% and >150% of SBW, and weight was adjusted by adding 25% and 60% of the excess weight to SBW for the two groups, respectively. The HBE equation with the adjusted weights predicted MBEE within ±10% for 78% of those subjects >125 to 150% of SBW and more than 60% of those >150% SBW. Although newer equations predict MBEE within ±10% in about 75% and 65% of the cases for normal weight and overweight/obese individuals, respectively, they are unlikely to replace utilization of the HBE in practice. Results of the present study indicate accuracy for the HBE similar to that of the newer equations in assessment of overweight/obese subjects with additions of 25% and 60% of excess weight applied to SBW for individuals >125 to 150% and >150% SBW, respectively.