I'm 51, played sports in high school and played football in college. After college and when I got married was the heaviest I ever was in my life at 6'1 and 250. Since then I've done P90X and T25 and both worked very well to get back in shape. T25 was nice because the workouts were only 25 minutes, and if you stick to the program and eat a reasonable diet, you will come out the end in excellent shape.
Once my kids got older and busier it got harder and harder to work out consistently. Fortunately they both decided to ditch traditional sports and committed to Olympic weightlifting in middle school. Eventually I started training with them and actually competed once in the master level in my late 40s. Unfortunately, poor lifting technique and injuries I never rehabbed correctly in high school and college caught up with me and I had to have shoulder surgery to repair a torn labrum (SLAP tear) and clean up bone spurs, etc... I tried lifting afterwards, but although surgery restored full normal function for day to day stuff, I wasn't able to clean and jerk at a high level any more.
Nowadays, my wife and I walk at least 4 days per week, hitting 3-3.5 mile routes on both paved and gravel walking trails nearby. Now that its warmed up we also mix in pickleball, which is one hell of a workout once you know the rules and learn how to play. Just be careful though, I'm a competitive guy and losing to my wife stings. In fact, its caused me to pull my groin and tweak my back going balls out to return shots I should just let go.
I'm holding pretty steady now at 6'1 and 225, but I fluctuate 5 pounds depending on time of year. Summer is tough with grilling, fishing, boating, and drinking. Fall is tough with Thanksgiving and Christmas feasts. There is one cliche that has proven true over and over the older I get. You cannot run or walk away from a bad diet. Work out when you can and eat a reasonable diet, limit your booze intake, and make sure you're eating enough quality protein. I've noticed more than ever that I cannot eat like I used to and expect to maintain my previous weight. I think most of it has to do with a loss of muscle mass and resting metabolism. As a result, I plan to resume squatting, deadlifting, and doing some moderate bench work. Getting started is half the battle though, and even though we have a gym in our machine shed, that 100 foot walk can seem like a mile most days. Self-motivation is tough, and you gotta find something that gets you out to break a sweat.
For those older folks taking creatine, what is a good rule of thumb, and do you start with a loading dose? I know that you have to keep your water intake pretty high as well. I appreciate any insight or tips.