Just step outside and walk. It doesn’t matter how far or how fast. The next day you’ll probably go a little farther. After a few weeks treat yourself to a decent pair of walking shoes. Amazon has tons of them.
At my shop I was the first to start walking on breaks. Now there are a bunch of people doing the same including the shop forman. Your neighbors will finally notice what you’re doing and some will do the same. You’ll make some friends and save some lives. It’s not just about you.
Auden
An important point about running training. Going slowly for 80% of your training is a proven strategy to go faster in races. It seems counterintuitive: go slower to go faster, but it has been proven to work and I can atest to its effectiveness (my n=1).
The reason it works is that at these slow speeds you are training the aerobic system and muscular endurance system, and these are the 2 main systems that are used in endurance running, of which 5k is a good example. You are using your aerobic system about 98% of the time in a 5k race. So the more aerobicalliy fit you are, the better. And slow running is a great way to do that. Why? Because you can do it day in day out. Refer the previous reply, you can do higher speed efforts and they definitely do benefit a lot of body systems, but you can’t do them day after day without bad consequences.
So the best running regime is 20% speed, 80% slow. And slow means really really slow. Could initially mean walking, but you should be keeping to a pace that you can comfortably continue a conversation. If you are even slightly gasping for breath when conversing, you are going too fast. So it is slow, and (IMHO) very enjoyable: just wait til the endorphins kick in. Woooooooooohooooooooooo!! 
♂
I love how this pairs with Keto. They both seem counterintuitive on their face value, but when you break it down and look at the science, both prove to be true.
Imagine the first guy who thought, I’m going to run slow to practice for a race and see what happens. I’m sure it didn’t come about like that, but you gotta figure there was some athlete at some point in time that was looked at as crazy… right up until he passed them all.
I am sure there were people who did it before, but the coach who first did this in a consistent way with his athletes was Arthur Lydiard (sp?), a NZ coach who had tremendous success with this approach. Various people have proved this true since then, most famously by Phil Maffetone, who coached Mark Allen to many World Ironman championships in the 80s.
His MAF method is still used by many today and is worth looking up if anyone is interested. It is essentially the keto method of running!
I read 80:20 by Matt something and he went through a lot of the history. It was interesting but a bit too detailed for me to remember it much. It did make a solid case for the near universal success of this method over other though.
I can’t say enough good things about swimming. Aerobic exercise and strength training all in one, and it’s easy on the joints. I also recommend water jogging/running. I used to teach classes and many of my students were rehabbing athletes who were looking for something easy on the joints, but that could vary in intensity, depending on your fitness level.
That being said, they key to exercise is to simply start moving. Finding something you enjoy is the key to sticking with it. If you can’t stand running, for example, there’s no point in telling yourself you’re going to run three times a week. Are there fitness classes in your area? Try a couple of different ones. Join a recreational sports league. Try yoga. Walk a neighbour’s dog. Do some gardening. It all helps!
I would love doing water exercise if I could find someplace that didn’t keep their pool water just slightly above freezing. I absolutely hate being in cold water. 
Yard work makes me forget to eat too, so there’s the added benefit of unintentional fasting.
I read a study the other day (tried to find it again but couldn’t) comparing HIIT to traditional cardio and there was no difference in calories burned or weight lost, but there was a HUGE difference in overall enjoyment of the programs in favor of HIIT.
The takeaway, as others have said, do what you enjoy!
That said, I’m a HUGE advocate of weightlifting for strength building and durability. And it’s SO important to find routines which focus on the entire body as SO many people have very underdeveloped posterior muscles (calves, hamstrings, glutes, and back). The great thing about weightlifting is you can actually incorporate HIIT into it. Do an exercise for 45 seconds with as much weight as you can handle for that time (reps are irrelevant, just go for time and good form), rest for 15-30 seconds, repeat, repeat again, then rest for 45-60 seconds, switch exercises. Repeat according to your program. Your heart rate WILL skyrocket during each set if you choose a weight that challenges you and drop a little between sets, skyrocket again when you start back up and drop again when you rest, and that’s exactly what HIIT does. I get my heart rate up to 188 bpm lifting weights like this (39 years old).
In my opinion, weightlifting under a HIIT style is FAR more productive for the average person than a traditional cardio HIIT program. Most people simply are not physically strong enough. High Intensity Interval Lifting (just coined that, I think) builds strength (more than HIIT) and cardiovascular conditioning (just like HIIT). If you want, do both HIIT and HIIL, alternate them.
Finally, if you can only pick one type of workout to do for the rest of your life, pick Yoga. It works everything. But realistically, toss Yoga into your routine once or twice a week with HIIL.
Okay, so apparently I didn’t coin “HIIL”, but I did come up with it organically. 
My view is that if I could only do one exercise it would be walking. It was fundamental to surviival before agriculture and is equally fundamental to independent living today.
Why does everyone stroll their babies? Because babies typically don’t cry when they’re strolling. That consistancy must have a genetic reason. I believe the reason is a noisy baby, when the troop was on the move, might compromise security and get left behind on the trail. Likewise, when the troop must move to follow a heard of grass eaters who have moved to fresh pasture anyone who cannot make the walk will be left behind and feed some preditor–unless buried before that can happen.
In my younger days I considered walking to be a wimpy old people exercise. I was wrong about that. May be it’s the most important exercise.
P.S. My house has a front porch close to the sidewalk. In the goood old days before television people would sit on those porches after dinner and greet friends walking after dinner. The front porch is a good place to surf on you tablet (TV is passe.) May be the side walk and front porches will make a comeback.
My dad got polio in his 20s. The most I saw him move was to hobble with a cane from one point to another. In his 80s, due to a car crash, his neck was broken and his hip/leg rejoined with a bolt. After that, the man just scooted around in an office chair. He lived to be 102 years old – after about 80 years absent the slightest muscle-building or aerobic activity. Take that n=1 for what it’s worth.
Pursue that which you enjoy. I have not found walking, jogging, tennis, racquetball, canoeing, bicycling, swimming, freeweights, resistance machines, or HIIT to influence weight loss, however, exercise does seem to reduce my appetite slightly.
I love picking up and moving sand, stone, soil, pavers, firewood, compost, snow, etc. So that’s what I do every day the weather allows because it keeps me very flexible, very strong, and very happy (endorphins?).
Pursue endorphins.
Exercise can absolutely influence weight loss. For the most obvious example, look at the nutritional requirements for athletes. Their caloric intake requirement to maintain their weight can easily be double that of someone of similar height, weight, and body composition. At the peak of my physical fitness at 31 years old, I was eating 4000 calories per day just to maintain my weight of 155 lb. Why? Physical activity ramped up my metabolism. The food I was eating (Paleo diet) also played an enormous role, probably the majority, but it is absolutely not fair or accurate to say that exercise does not play a role in weight loss.
Fact is, you can’t exercize your way out of a bad diet. Not even professional athletes.
Ah, porches. I once lived in a Victorian with a huge porch (veranda, as my great-grandmother called them.)
Exercise makes the diet part easier for me. My resting metabolic rate is a measily 1430 calories. In the past 7 days my exercise calories averaged 680 per day (most of that was walking). That’s about 35% of my daily calories burned. Currently I eat about 300 surplus calories per day on average, 1430+680+300, then eat nothing on Saturday to balance the surplus. I want to add some muscle without adding fat. I couldn’t do this without Cronometer.
Of course not. And I don’t recall anyone, ever, saying you could.
But, saying that “exercise plays very little role in weight loss” and saying “you can’t exercise your way out of a bad diet” are both very, very flawed ways of thinking. Even entertaining those notions illuminates a flawed mindset, IMO.
I know that some folks do a lot of running (which can be great if you love it!) but from what I’ve seen the faulty CW on exercise is generally focused on lots of aerobic work, with the faulty assumption that calories are the basis for weight loss.
If you’re doing it right, exercise will contribute to weight loss/maintenance and health (and help you look terrific!).
I would look into resistance/lifting, occasional HIIT or sprints, and supplementing those with plenty of moderate movement (walking plus anything that you enjoy doing!).
Body By Science is a very compelling protocol, and the book goes into how very slow resistance work is some of the best exercise we can do. A very similar approach is Slow Burn, and @SlowburnMary has some terrific posts about it on the forum.