Strength-training done correctly is filled with benefits. There are no negatives. What's more, we know these benefits not only improve us but also our quality of life, so the question isn't whether you're too old to work out but whether you're too old to improve your quality of life. The answer to this should be a resounding no. Strength-training done correctly is only ever beneficial. There are no negatives. In fact, a wide range of research, results, tests and accumulated statistics all support and expound the amazing benefits of strength-training. A simple 1-hour online search will confirm this to you.
If you're not too old to improve then you're not too old to work out.
You choose.
I find it weird how in today's soft-cock, politically-correct glasshouse we're all so quick to stand against racism, sexism, ageism or whatever "-ism" twists your knickers but we write ourselves off quickly, silently and with no protest. Don't be that guy. Don't buy into your own age-ism bullshit. Don't wilfully allow ideas, perceptions or simply pure fantasy about "growing old" prevent you from starting a straight forward strength-training program filled with benefits. Below is but a mere fraction of said benefits, some of which will surprise you. I see no reason you shouldn't be reaping these benefits regularly.
You get strong
Strong muscles are bigger muscles. You don't get strong skinny men. Strength not only means you can do pretty much more of anything easier, it also means you can build upon that, furthering your lifting goals. You'd be surprised how much better your quality of life can be when you're strong physically, mentally and emotionally. It's a confidence builder like no other.
You get fitter
People don't realize the cardiovascular benefits of weight training. Bang out an explosive set of moderate-weight squats and you'll know what I mean. Do a set of bent-over rows, hauling the bar into your midsection and you'll be sweating. Work up to a max deadlift single and mate, you'll be ready to assume the foetal position or something close to. Your lung capacity and endurance will expand exponentially.
You lose weight
For older males this is important. We pack fat onto our stomachs inside and out, as well as round the hips. I should know: I have love handles. I could diet them away but I don't want to diet, full-stop. I value my beer intake. But. You will slim down. You will look better. You will feel better too. Let's face it: looking good to ourselves is important to, well, ourselves. No, I didn't get into this to look good, I got into this for me but I do like the changes I've made. I like the improvements in musculature, shape, strength and endurance. Don't be ashamed of that.
You form good habits
You may already have good habits (I didn't particularly in fact, I was a smoker for 15yrs) but once you get religious about weight-training you will form a habit for life. I intend doing this till I can't. Which I reckon should take me into my nineties whereby I can die confident. Anyway, making good habits in one area tends to have cross-over into making good habits in other areas. Usually. Whilst I don't follow any set diet I've certainly improved in my food choices and over-all nutrition. If you're getting strong and fit you don't want to counter this by eating like a mutton-head and by that I mean consuming regular amounts of junk foods, sugars and the like.
You'll feel alive
This is big: you'll actually feel like a man again. You'll have a purpose. You'll have a secret double-life no-one needs to know about whereby you sweat and pant alone in your garage pushing and lifting all manner of weight which makes you harder. We all need to harden up to some extent: I certainly did. What's more, this too has cross-over into how you carry yourself and how you view yourself. It doesn't make you bullet-proof but it does provide proof that you can bite the bullet and get shit done. That has to be good for you (feel free to use the previous line as your go-to quote; it's a goody).
You only need a small amount of equipment
I have a barbell, two dumb-bells, a flat-bench and some 160kg+ of iron. That's it. I actually built my own rack for bench-pressing and squatting and it's still going (if I feel inspired I'll put the design up on the site at some point for those DIY-minded amongst us). Over the years I doubt I've spent more than $300 on all the above whilst my wife's 6-month gym membership was roundabout $450.00 so you do the math. Fact is, you don't even need the dumbbells. A bench that provides the capacity to squat out of and a barbell and weights is all you really need.
Your knowledge base will expand
I'm often pleasantly surprised just how much I've learnt over the years about my strength-training-hobby-slash-addiction. It's nice to be able to offer advice about things you've done, programs you've used, criteria you actually understand with novice or professional. What's more, most of the movements you learn cross-over into life whereby you find yourself bending correctly, lifting correctly and generally being more aware of how to move "weight" and how much weight you're capable of moving.
Your metabolism ramps up
More muscle means a faster metabolism, hence the reason many of today's powerlifters and bodybuilders eat like the Hulk. No, that's not the sole reason these types of athlete consume such vast amounts of food, but the point I'm trying to make here is physical exercise increases appetite due to energy depletion: your body needs energy to move and groove. We get that through food, particularly carbohydrates or "carbs" (that's another article). My appetite climbed significantly once I started pushing weights even as I lost weight.
You don't have to go heavy
Over the decades bodybuilders -- by the way, I'm not a bodybuilder -- perfected the art of moderate weight at higher volumes to increase muscle mass. All sorts of programs exist out there where you don't have to go heavy yet will still make impressive gains. No, bodybuilders didn't just hoist weights repetitively and grow; most importantly they ensured they ate protein-heavy diets that aided in both recovery and growth (which is where today's supplements and their ilk come into play, I suppose). Whether you go low reps at heavier weights or high reps at lighter weights, you'll still make gains. You can still attain your full potential.
You'll enjoy the spill-over effect
One guy I know has this thick, impressive neck yet does absolutely no neck work. It came as a result of "spill-over" from his squats, deadlifts, benchpress, shoulder-press and cleans. Others develop meaty forearms and calves yet do zero isolation on either body part; again, they are reaping the spill-over effect. It's not something anyone can accurately surmise. Rather, it's something you discover as you go along. My spill-over was in my shoulders or to be more specific, my deltoids: I hardly did any overhead pressing and did exactly zero lateral-raises or any isolation-fly-type-movement for them at all, yet they grew.
You're health will improve
This more than anything (in my opinion) should be the goal of the mature lifter: physical health. It is your physical health that engenders the quality of life you deserve -- not looking good, not getting "big", not pushing-slash-pulling big numbers but overall health and longevity. Nor is said "health" limited to your muscular system. Your skeletal system strengthens because bone is a living tissue; weight-bearing exercises force bones to strengthen thus increasing bone density.
Your respiratory system is strengthened such that lung capacity increases and your body becomes more adept at oxygen distribution. Your cardiovascular system (i.e. heart & blood vessels) functions are improved, reducing heart-related issues now and in the future. Even your lymphatic system can benefit from exercise which increases white blood cell count, thus boosting immunity. The list goes on.
:: CONCLUSION
As we age we weaken and lose size, shape, posture and endurance. Our mobility suffers, our endurance levels drop and we feel a strange compulsion to purchase knitted cardigans. However, we still have an enormous capacity to improve upon these events and yes, even reverse them, but unfortunately far too many of us buy into the now-I'm-50-I-should-slow-down mantra. That ain't kiwi, fella. As you can see from the above, the pros far outweight the cons and it's time we all did a rethink and stopped writing ourselves off so quickly. Kia ora whanau.