Amyotrophic lateral sclerosis (ALS) is one of the fatal motor neurodegenerative disease that is well characterized by the progressive muscle weakness and atrophy in adults that occurs in familial and sporadic forms. Even though dysphagia is a usual outcome of the disease, nutrition and metabolic status of ALS cases has been received slight attention. The cause of neuronal death in (ALS) patient is uncertain but seems that mitochondrial dysfunction may play an important role. Ketones promote mitochondrial energy production and membrane stabilization. To determine if a ketogenic diet (KD-The body burn fat for energy instead of glucose). (KD)alters the progression of weakness, motor neuron survival and mitochondrial function in G93A transgenic ALS mice. We fed transgenic ALS mice model with a KD formulation. Motor performance, longevity, and motor neuron counts were measured in treated and disease controls. We found that blood ketones were > 3.5 times higher in KD fed animals compared to controls. KD fed mice lost 50% of baseline motor performance 25 days later than disease controls. KD animals weighed 4.6g more than disease control animals at study endpoint; the interaction between diet and change in weight was significant. In spinal cord sections obtained at the study endpoint, there were more motor neurons in KD fed animals.Our study shows that diet, specifically a KD, can alter the progression of the clinical and biological manifestations of the G93A SOD1 transgenic mouse model of ALS. These effects may be due to the ability of ketone bodies to promote ATP synthesis.