Rationale: The increase of resting energy expenditure (REE) variation in ALS is a prognostic factor for the survival mainly in patients with a REE variation over +20%. Measurement of REE by indirect calorimetry (IC) compared to REE predicted with formula (Harris and Benedict [HB] 1919, HB 1984 or Mifflin) is necessary to obtain the REE variation. However, IC is not available in many centres. Jésus et al. formula is a validate formula to predict REE in ALS and can be used in the absence of an IC. The aim of this work was to study the survival of ALS patients according to REE variation with IC or Jésus formula. Methods: Nutritional assessments and body composition fat-free mass (FFM) and fat mass (FM) (by bioimpedance analysis) were performed in ALS patients at diagnosis. REE was measured by IC (mREE) and by Jésus formula (Jésus REE) using FFM, FM and sex. cREE was calculated using HB 1919, HB 1984 and Mifflin. REE variation (%) was calculated according to the formula: (mREE or Jésus REE) – cREE / cREE * 100. Survival was studied by Log-rank test (Hazard Ratio [HR], confidence interval [CI] 95%) according REE variation under or over 20%. Results: 395 ALS patients with a median age at IC of 66.8 years (Interquartile range: 58.6–74.1) with a sex ratio of 1.1 were included. Median body mass index was of 22.4 kg/m2 (22.2 – 27.5). REE was of 1500 kcal/24h (1274 – 1708) with IC and not significantly different than with Jésus formula 1500 kcal/24h (1291 – 1679) (p=0.83). With REE measured by IC, REE variation over 20% was found in 21.0%, 18.0% and 43.0% with HB 1919, HB 1984 and Mifflin formulas as cREE respectively. With Jésus REE, REE variation over 20% was found in 5.1%, 1.5% and 25.6% with HB 1919, HB 1984 and Mifflin formulas as cREE, respectively. REE variation over 20% was more frequently found using IC than with Jésus formula (p<0.0001). Survival according to the IC and Jésus formula with HB 1919 and Mifflin formula as cREE is presented in table 1. With HB 1984 survival was not significantly different in ALS patients with REE variation under or over 20%.