For anyone in the US, you can ask your primary care doctor for a referral to a Registered Dietician if you are having issues with excess body weight, limited muscle gain, or other diet related health concerns.

Body weight really is all about calories in vs calories out regardless of age. Eating bulky vegetables is often recommended because they are filling without being calorie dense (as well as the vitamins). Low intensity activity (standing, walking, gardening) is associated with the largest decreases in body weight because it does use some calories but doesn’t increase appetite as much as high intensity exercise. Although some exercise is still good to keep up muscle mass and heart health. Yes, as you age it can be more difficult to create/maintain muscle mass as your biology changes, but there are always health benefits to eating healthy and staying active.

I really like the Nutrition Source for science-based nutrition information in case anyone is interested!