When I say “activity” I don’t mean making your day busier than it already is. I almost used the word “exercise” but that’s not really accurate either.
In the last 6 months or so I’ve lost over 20 lbs. I got motivated to do something about my weight when I noticed that I was losing pounds just by adopting a more active lifestyle. Hello Weight Watchers! 
I bring this up because exercise is an amazing tool for helping your ADHD symptoms, especially focus and concentration.
I’m no fan of exercise, but here are some things I did to just bring my activity level up at first:
1. I started parking farther away from where I needed to go. You don’t have to park at the very end of the lot, but park farther away than you would normally. Every little bit counts.
2. I noticed how much my husband moves when he’s home. The man doesn’t know what having a weight problem is like. I felt guilty sitting on the couch while he was up and doing things, so I got up and started moving. You can always find things to do around the house. And if you can’t, come over to mine.
3. I bought a fancy pedometer called a Striiv. It keeps track of my steps and when I go up stairs. It has all kinds of ways to motivate you - games, challenges, and even donating to charity. You can read more about it on their site. It really is a great motivational tool.
4. I bought myself some nice athletic clothes. You know, yoga pants and warm up pants, a good pair of shoes, and some nice tops. Then I kind of went crazy and got new sunglasses and a jacket or two. Anyway, they make me feel good and they do motivate me to move more.
5. I kept things simple. All I basically do is walk. I can do that on the treadmill at the gym or anywhere else I happen to be. And in the process, I’ve learned that I like to do 5K races. I’m no runner yet, but I will be.
I can definitely tell the difference in the way my brain works since I started this program. My head is clearer and I am more focused. I noticed the positive effects almost immediately, but I especially noticed what happened after I broke my arm and had to rest for a few weeks. (I did attempt a 5K about a week after I broke my arm - not the best idea and also against doctor’s advice.)
That time of doing more resting than moving put my brain back into foggy ADD mode.
You really do need to try this to experience the wonderful effects that added movement can make to your brain. Think of it as activity rather than exercise if that helps.