HOW OFTEN AND HOW LONG SHOULD YOU EXERCISE?

Depends a lot on age, fitness level, what you're doing and what the end goal is. If just weight loss and not doing lifting to save muscle could easily get by with HITT / circuit training for 20-30 minutes a day and be fine. If you are doing lifting probably 1 hour a day depending on the program and some cardio after. But age really comes into play at 47 I can't lift and do cardio like a 17 year old. But listen to your body this is not a sprint if you have to take a day or even a week off to recover do it.

I personally do 45-60 minutes lifting (heavy for strength) and cardio 5 days a week with about 45 minutes lifting and 10-15 cardio. Also have scheduled deload weeks every 8 weeks. But do what fits your schedule and your life weight loss is done with your diet and not in the gym.

As for exercise calories and eating back I started doing about 50% but inaccurate burn was hard to get right so I went with https://www.muscleforlife.com/tdee-calculator/ and just give myself a higher calorie goal per day/week and do exercise without worry about the burn.

a lot of this comes into knowing your body. and that takes time.

ive been doing this 5 years now. i workout (mostly cardio) anywhere from 2-5 times a week (5 is always my goal but 3-4 is my average, cause .... life as a single mom). as far as eating back calories .... sometimes i do, sometimes i dont. depends on if i am hungry and how im feeling.

If it's a new thing, ramp up gradually, starting with moderate intensity activity, perhaps 3 days a week. When that starts to feel manageable and good, consider adding other days, maybe varying the activity. Keep intensity lower for a month or six weeks, then start phasing in more intensity, but always allow one day between really intense workouts of the same type (like heavy lifting for the same muscle groups, or intense cardio).

Ideally, you want exercise to be fun, and energizing (after maybe just a few minutes of "whew!" feeling right after the workout). To get the best weight management benefits, you don't want to be exhausted and dragging through the rest of your day. If that happens, it saps calories from your regular daily activity (do less, sit/sleep more, etc.), and on net you burn fewer calories. (Non-exercise daily activity like job, chores, family, etc., account for more calorie burn, for most people, than exercise does. Exhaustion/fatigue reduces those.)

The right duration/frequency is what stays fun and energizing, and fits well into good life balance as you personally define it. That means having time not only for exercise, but also your job, family, social activity, non-exercise hobbies, and anything else that's really important to you. No one else can tell you how much time that is. Last I looked, IIRC, the basic US official recommendation was 150 minutes weekly of activity that raises heart rate, and 2 days of strength training. So, that could be good to shoot for, if it fits into your life.

Definitely eat back at least some exercise calories, if you let MFP set your calorie goal, especially so if your weight loss target is aggressive, and you're doing relatively much exercise. MFP built a calorie deficit into your basic calorie goal before exercise (assuming you followed instructions and set your activity level based on your job, home, and other non-exercise activity). Under-eating is a recipe for fatigue and weakness, and you don't want that.

Many people worry that exercise calories may be over-estimated. If that worries you, eat back 50% to start, monitor for 4-6 weeks, then adjust your calorie goal if needed.

I'm a li'l ol' lady, and retired, age 62, now in weight maintenance at 5'5", low 130s. I've been quite active for around 15 years now. It's summer, so I'm rowing (on water) 4 days a week when weather permits (on the water about an hour and a half), going to a 45-minute spin class 2 days, strength training 2-3 days for around 40-45 minutes, and throwing in some random bike rides or walks or whatever. ATM, I'm also rowing and doing related activities another 3 evenings a week, helping with my club's learn-to-row class, but that's temporary. This works for me, because rowing is pure fun, I enjoy my spin classes, I get a mix of activity, and (because I'm lucky to be retired) I still have time for other hobbies and chores. Only you can determine what will work for you.

Best wishes!