The Wahls diet is a modified Paleolithic diet that emphasizes dark green leafy vegetables, colorful fruits, high-quality animal proteins, and omega-3 polyunsaturated fatty acids, while limiting grains, legumes, dairy products, sugar, and processed foods containing proinflammatory omega-6 fatty acids. The Wahls diet may reduce inflammation, oxidative stress, and mitochondrial dysfunction and has plausible mechanisms for slowing amyotrophic lateral sclerosis (ALS) progression. However, research on its dietary components in the ALS animal models has yielded conflicting results. Though multiple cohort studies suggest high carotenoids, omega-3 fatty acids and fruit intake are associated with reduced ALS risks, neither the diet nor its components has been demonstrated to slow down ALS progression in case studies or clinical trials. On the contrary, the Wahls diet, a restrictive, low-carbohydrate and low glycemic index diet, caused an average weight loss of 7.2% BMI in multiple sclerosis clinical trials, which is a significant concern for people living with amyotrophic lateral sclerosis (PALS) as weight loss is associated with faster ALS progression and shorter survival. Considering the above, we cannot endorse the Wahls diet for slowing ALS progression.