Things like Chicken, bone broth, grass fed beef, liver etc. Not fish/eggs/any other animal products
Protein is necessary to provide substrate to maintain muscle mass. Conversely, autophagy and caloric restriction, have shown increases in longevity (ie delay of age related illness) animal models. Its important to cycle from build to burn states to maintain mitochondrial health which plays a key role in longevity.
Eating less meat is better than eating more meat. Small amounts of meat are beneficial when compared to large amounts of meat, but detrimental when compared to a low fat whole food plant based diet that minimizes saturated fats and processed foods.
It’s all relative. What are you comparing to “small amounts of meat”?
Are we talking about cosmetic anti-aging or life-extension here? In any case, meat (including fish) could help. It’s not the end all be all, though. No one food group should be regarded as the sole solution to your problem. Balance is key.