Increased resting energy expenditure compared with predictive theoretical equations in amyotrophic lateral sclerosis

Approximately 50% to 60% of amyotrophic lateral sclerosis (ALS) is characterized by an increase in metabolic rate. The Harris and Benedict (HB) 1919 formula is the equation mainly used to calculate resting energy expenditure (cREE) compared with measured REE (mREE) by indirect calorimetry (IC), but other formulas are also applied in current practice. The present study aimed to assess mREE in patients with ALS compared with 12 cREE formulas and study the relevant threshold of REE variation to screen patients with a higher evolving risk.

Nutritional assessments and body composition (by bioimpedance analysis) were performed in patients with ALS. mREE was measured by IC, and cREE was calculated using the HB 1919, HB 1984, World Schofield, De Lorenzo, Johnstone, Mifflin, World Health Organization/Food and Agriculture Organization, Owen, Fleisch, Wang, Rosenbaum, and Nelson formulas. Functional and respiratory evolution and survival by log-rank test according to two thresholds of REE variation (10% and 20%) were studied.

A total of 315 patients with ALS were included in the study. The median mREE was 1503 kcal/24 h (range, 1290-1698 kcal/24 h), which was higher than all predictive equations (P < 0.0001). Depending on the predictive equation, REE variation >10% and 20% was found in 35.2% to 76.3% and 14.6% to 53.3% of patients with ALS, respectively. Patients with an REE variation >20% with HB 1919 and HB 1984 had a lower survival. Moreover, with this same threshold and the Mifflin formula, patients had higher functional and respiratory evolutions and lower survival.

The increase in metabolic rate is present according to the different cREE formulas used compared with IC. In clinical practice, REE formulas (e.g., HB 1919, HB 1984, or Mifflin) can be used as a reference value compared with IC to screen patients with ALS with an REE variation >20% and a higher evolving risk.