I do a lot of exercise that requires almost 0 effort (my personal opinion) and little if not no strain on your joints.
I have a pilates ball and yoga mat that live next to my sofa. We are great friends. I use them daily along with a couple of elastic bands (large widths and different lengths) and a few light hand weights.
I started by just getting comfortable on the ball, sitting with it placed against my sofa for extra security to prevent it from rolling away. (if you have carpeting or a carpet you don't need the mat) I face my sofa, straddle the ball more or less (legs sort of in front of me and slightly open to either side for balance) and then just bounce a little while sitting up straight and tucking my tummy in as tight as I can. (I hold my arms out to my sides or in front of me, sometimes holding weights but that is later on)I breathe deeply, bounce and get my centre of balance...never taking my feet off of the floor. Then I try to roll a bit side to side or back to front...sometimes I do small circles. Always with my tummy tucked, back straight.
The more comfortable I got, the wider the circles, the higher the bounces. Eventually, I scooted down, with my lower back resting on the ball, my feet against the side of the sofa (or your feet up on the sofa for more stability) and push off a bit with a sort of forward/backward motion. As the ball sort of scoots back you get it settled in the middle of your back, your feet against the sofa and your butt sort of in the air..you raise and lower your butt in the empty space.
I can now read in this position, just rocking back and forth.
This is the most amazing ab exercise routine that I have ever had...my abs tightened naturally, without too much effort, and as time goes by my stomach gets flatter and flatter without any strain on my back or hernias.
I now have a 1/2hr routine that I do, on, beside and draped over the ball.
I use the mat with my legs over the ball to do planks & leg lifts too but that is much later once you get used to the work. I am training my chiro in this as well as some of my other student. They cannot belive that a woman my age can spend an hour without any difficulty doing this...My abs are as hard as steel.
There are dozens, literally, of videos on the internet but my only real advice is to enjoy yourself and have fun on the ball, play until you find your center of balance and then work on it...it is great for pain relief, posture and abs...
As for diet? I hate the word.
I reduce intake, increase output and give myself a couple of rules when I need to drop a couple of winter pounds.
1. No fried foods.
2. No peanut butter or other nut butters (I have 0 self-control...Better to not start)
3. No ice cream (try Italian ices instead or sherbert...less fat)
4. No bread, cake or potatoes. Whole grain pasta and rice are fine every now and then
5. Lots of homemade soups and stews (more liquids fewer solids) I use a pressure cooker, throw every veggie I've got hanging out in the bottom fridge drawer (zucchini, squash, celery, spinach, pumpkin, tomatoes...), add fresh herbs (parsley, cilantro, garlic, onion...) and cook for 10mins. Then I blend with an immersion blender. Add spices. It is always different, thick and yummy and very satisfying...Add some grated cheese on top and it becomes rich and filling.
6. Artichokes, zucchini, eggplants and avocados are your friend. Eat them without limits. I can make a meal out of a grilled eggplant, some parmesan cheese and tomato sauce.
7. Do not neglect meats, fish, chicken and eggs...they are all good quality proteins and help you to maintain muscle mass.
8. Avoid all commercial sauces. Barbeque sauce, ketchup, salad dressings are all full of sugars, salts, chemicals and stimulate the appetite. Use olive oil, mustard, vinegar or balsamic as sauces or dressings. You control the contents and salt that way.
9. Avoid most industrial foods. Stick to things with short lists of ingredients. If you cannot understand the label of need a translator then do not buy it.
10. Dark chocolate is your friend. It is flavorful, satisfying, and does not have a lot of calories, it contains magnesium which is a feel-good mineral. It also helps you with your sleep cycles.
11. Ditto for cocoa powder. Put it on or in plain yoghurt and you have a great treat.
That is pretty much it.
I do not need a specific diet, rules and regulations, made up by some expensive stranger, scales, points or books...just common sense; I eat and enjoy my food, binge occasionally when stressed out, nibble on black liquorice and dark chocolate, eat lots of fish and do not sweat it too much.
My body is smarter than me, it knows what is good for it, automatically regulates itself, craves foods that I need (spinach? Lemons...) and finds its balance if I allow it to.
That's it...I hope that some of this helps.