An average healthy person needs 0.8 gram of protein per kilogram(kg) body weight to meet daily protein needs. So a 150Ib person would need 54gm pf protein per day (150Ib / 2.2= 68kg.... 68kg x 0.8=54gm). Keep in mind that those who are more physically active or those who want to gain muscle may have increased protein needs.
Physical activity like cardio or strength training will help to preserve muscle mass.
Regular exercise is imperative to maintain muscle.
Animal based food sources contain the highest protein content (meat, poultry, seafood, dairy products), but plant based foods can also adequately meet protein needs (nuts, seeds, grains, beans, lentils, soy products).
Eat Well, Live Well.