Separate from caloric restriction, can substantial restriction of carbohydrates (i.e., ketogenic diets) increase longevity by reducing insulin levels?

The body of research doesn’t include a clear answer to this question. The idea that reductions in insulin production and insulin action might increase longevity is intertwined with the “rate of living theory of aging”. There is some observational evidence in humans^[1] to suggest that lower levels of insulin might be associated with longevity, and there is interventional data in rodents^[2] and worms^[3] implying that insulin may influence longevity. However, this hypothesis has similar limitations to those mentioned above in that there is a lack of experimental evidence in humans to support the idea. Currently, there is not enough evidence to suggest restriction of carbohydrates (and associated reduction in insulin) increases longevity in humans.