IMPORTANCE Because dietary intakemay influence pathophysiologic mechanisms in sporadic amyotrophic lateral sclerosis (ALS), the association between premorbid dietary intake and the risk of sporadic ALS will provide insight into which mechanisms are possibly involved in ALS pathophogenesis. OBJECTIVE To systematically determine the association between premorbid dietary intake and the risk of sporadic ALS. DESIGN, SETTING, AND PARTICIPANTS A population-based case-control studywas conducted in a general community setting in the Netherlands from January 1, 2006, to September 30, 2011. Analysis was conducted April 1, 2013, to November 15, 2014. All patients with a new diagnosis of possible, probable (laboratory supported), or definite ALS according to the revised El Escorial criteria were included and multiple sources were used to ensure complete case ascertainment. Of 986 eligible patients, 674 gave informed consent and returned a complete questionnaire; 2093 controls randomly selected from the general practitioners’ registers and frequency matched to the patients for sex and age were included. MAIN OUTCOMES AND MEASURES We studied the premorbid intake of nutrients in association with the risk of ALS by using a 199-item food frequency questionnaire adjusted for confounding factors and corrected for multiple comparisons while minimizing recall bias. RESULTS Presymptomatic total daily energy intake in patients, reported as mean (SD), was significantly higher compared with controls (2258  vs 2119  kcal/day; P <.01), and presymptomatic body mass index (calculated as weight in kilograms divided by height in meters squared) was significantly lower in patients (25.7 [4.0] vs 26.0 [3.7]; P = .02). With values reported as odds ratio (95%CI), higher premorbid intake of total fat (1.14; 1.07-1.23; P <.001), saturated fat (1.43; 1.25-1.64; P <.001), trans-fatty acids (1.03; 1.01-1.05; P <.001), and cholesterol (1.08; 1.05-1.12; P <.001) was associated with an increased risk of ALS; higher intake of alcohol (0.91; 0.84-0.99; P = .03) was associated with a decreased risk of ALS. These associations were independent of total energy intake, age, sex, body mass index, educational level, smoking, and lifetime physical activity. No significant associations between dietary intake and survival were found. CONCLUSIONS AND RELEVANCE The combination of independent positive associations of a low premorbid body mass index and a high fat intake together with prior evidence from ALS mouse models transgenic for SOD1 and earlier reports on premorbid body mass index support a role for increased resting energy expenditure before clinical onset of ALS.