This isn't exactly addressing your specific questions, but ...
I'm in my upper 50's and have been overweight my whole life, but in the last 10+ years it got very out of control. I'm 6' 5" (maybe shrinking in height a little), and I was approaching 400 lbs!!! I started into pre-diabetes and my hips and knees started complaining about the weight, so I decided I had to really do something about it.
Since August, 2016 I have lost almost 110 pounds by changing how I eat AND tracking what I eat. I tried to exercise by walking at the beginning, but the hips, knees, and feet simply hurt too much. The walking for exercise just wasn't working.
I used an Android app called "Value Diary", which uses a version of Weight Watchers (WW). It assigns you a daily number of allowed points based upon your height and weight. The reason I like WW is that it cuts carbohydrates and allows free (relatively unlimited) fruits & vegetables. It recognizes that low fat proteins are good for you. I stopped eating bread (mostly), pasta, rice (mostly), cereal, ... and I track EVERY bit of foot that I eat. If I can't find it in the database or can't enter the nutrition information, then I just find something close - I figured a worst case guess was better than not recording it. You just have to DO IT and be honest - DON'T CHEAT, YOU ONLY HURT YOURSELF!!
Oh, and my wife did the same thing. I just couldn't do this on my own. She wasn't nearly as heavy as me - smaller of course, but she lost 30+ pounds and is very happy about it - except for having to give up her beloved high calorie coffee creamer - the WW points didn't let her get by with that.
At first I ate some rice each day, but my doctor said it provided no real nutrition and was only empty carbs, so I stopped (mostly).
I also weigh myself every morning - keeping in mind that the weight will go up and down a bit on a daily basis - so I try to not let short-term increases upset me. Sometimes it still does, but hey.
I try to only eat eggs, lean meats - chicken, lean ham, lean pork chops, lean red meat, fish (I'm not a big fish eater), chicken or turkey sausage, ...
I found commercial reduced calorie frozen dinners to be too little food and not satisfying.
Breakfast used to be toast (2 slices) with peanut butter, or a big bowl of cereal. Now I scramble two eggs in a bowl (using Pam), cook it in a microwave, toast one slice of whole-wheat bread, put a slice of low-fat cheese on top of the toast, and lay the cooked egg on top. That and a glass of skim milk.
Lunch is typically a salad (at work) with some hard boiled egg and chicken slices (veggies unlimited), and non or low fat dressing. I find some parmesan cheese sprinkled on add a lot of flavor - and lots of fresh ground pepper, when available. When eating out I try to go to Subway for a turkey sandwich with no sauces, or Taco Bell for tacos with Fresco sauce (no cheese). I haven't eaten a burger or pasta since I started.
Dinner is usually a salad, fruit, a hot veggie, and a lean meat, with skim milk. I found that veggie pizza is tolerable if I am careful the rest of the day. No fried foods (except meat in a little oil - but not deep fried or breaded, if you know what I mean).
I eat a snack - usually a granola bar (watch the points!!) at 10am & 2-3am, trying to avoid getting too hungry. I tried eating nuts, but they were high in points and my gut doesn't seem to like them much. Oh, and I have a WW fudge bar at night - it's about the same points as a granola bar.
Now, a smaller person may need to avoid some of my foods - they are allowed fewer daily points. It could be done by skipping the breakfast cheese and bread, skipping the egg or chicken with lunch, and looking for lower point snacks - maybe veggies.
I would strongly strongly recommend changing how you eat. It can make ALL the difference.
These days I can walk a lot farther and do a lot more without the pain. So now I am walking more - parking far away from wherever, walking up and down parking ramps, taking dogs for walks, etc. I still have more to lose, but getting there.
Ken
P.S. I think walking is really the best exercise you can do if weight is an issue. You just can't get enough exercise inside - except maybe using a treadmill, but if you're obese it will be very tough going. My solution was to loose weight first, and then start walking more.