Increased total daily energy expenditure in mild to moderate ALS: greater contribution from physical activity energy expenditure than hyper-metabolism

Objective: It is unknown whether the relative contribution to energy imbalance in amyotrophic lateral sclerosis (ALS) is due to decreased energy intake, or increased energy expenditure from hyper-metabolism and/or physical activity, or both. Methods: We studied 10 free-living sporadic ALS subjects with mild to moderate disease and 10 matched healthy controls to address this question. We estimated energy intake by 24-h recall in ALS subjects and three-day food diary in all. We estimated body composition by dual energy X-ray absorptiometry and resting metabolic rate by indirect calorimetry; and measured total daily energy expenditure (TEE) and physical activity-energy expenditure using doubly labeled water. Results: Daily energy intake was no different between ALS subjects and controls. Despite lower fat-free mass, unadjusted TEE was higher in ALS subjects than controls (2844 ± 319 vs. 2505 ± 261 kcal/d, p = 0.005 by paired t-test). Compared to controls, hyper-metabolism occurred in 80% of ALS subjects. Physical activity-energy expenditure was higher in ALS subjects than controls (718 ± 262 kcal/d vs. 487 ± 196 kcal/d, p = 0.04). In controls, energy intake matched TEE; in ALS subjects TEE was higher than energy intake. Conclusions: We found higher TEE in ALS subjects than controls, with larger contribution to difference from physical activity-energy expenditure than hyper-metabolism. Although daily energy intake in ALS subjects was similar to that in controls, they were unable to compensate for increased energy needs. To accurately determine energy balance and optimize nutrition in ALS, future studies should consider measuring energy intake, energy expenditure, and physical activity.