Life can extend because autophagy is the fountain of youth. And autophagy are induced by either fasting or low protein diet. That's why vegan people look younger and live longer and all the blue zone people are eating low protein diet.
The traditional Okinawan diet are mainly sweet potato, rice and all kinds of vegetable. Very little meat and fish. Those are all reserve for special occasions.
It's always predominately plant-based diet allow human to live the longest.
Therefore by adding animal products to your regular diets, it will negate the result of your fasting effort. Many keto diet promoters have sudden deaths with heart related conditions, it is well known fact from news.
Ketosis can easily achieve by early morning fasted cardio or prolong fasting. Using diet to achieve ketosis is a suicide mission.