Usually, when people ask how many times a week should you work out it's about some form of weight training, so that's what I'm dealing with.
The answer is of course "it depends", but we all want a definitive number to work toward, so in some ways that is part of what I think is wrong with this question, but don't click away just yet....
I'd really like to help you find that number (or range of numbers), so please keep reading, especially if you struggle with motivation and/or consistency (or feel like you can never get it right).
A lot of the time, the question of wanting to know the number of days a week to lift weights comes from a desire to get things "right" or "best" for a certain goal. Many times it will be answered by a well intentioned trainer who will simply address it from that perspective.
You'll hear a typical black and white answer of:
For hypertrophy, do X number of days
For strength do Y number of days
For general health (aka fat loss) do Z number of days
However, I believe there's a better way to ask this question or, for the trainer, a question to ask in response:
How many times a week will I/you (realistically) work out? Then get a minimum and maximum.
Then the conversation can go toward making a plan for how it will happen. The client has the answers/resources, and the trainer is, well, a coach.
As a fitness professional/expert, I believe it's our job to steer the person toward finding something that is suitable for their current stage. It must be doable, but with room to grow into. In other words, there's pacing built in.
You see, within this simple question lies a truth about most fitness goals for most people (excluding athletes or those getting ready to compete):
Whatever frequency (and other factors) is going to be sustainable is what you should do. Because the reality is, weight training even at a frequency of once or twice a week will give many of the same benefits as higher frequency.
Sometimes, you'll have a super enthusiastic response of "I will lift 7 days a week", because there's still this notion out there that "more is better", so I have started asking people whether they'd be curious to find what their minimum effective dose is. Often, they'll say yes, but they are a little scared by the idea of doing less than they believe they should (this, again, is based in all or nothing, black and white influences from the fitness world and western culture at large).
Now, of course it can take a little time to actually discover that minimum effective dose AND this number can fluctuate week to week for many people, so yet again, we're faced with a question about details that really aren't so black and white. For true success (which I believe is contentment on the journey + good enough results) the root lies in remembering the big picture. What will allow you to be consistent?
Here's another thing:
When people imagine doing lower frequency training (say 2 workouts a week), the typical advice is to "make up for" lower frequency with more volume (either sets/reps and/or load), which can impact the duration of the workout. Yet again, we may run into a stumbling block for some people who really have very little time or energy to go "hard and/or heavy".
The question, therefore, should be framed from the perspective of the individual asking it. You have to start somewhere that's doable, and find out what other things motivate the person to show up (see my recent post about how to get motivated to work out).
Case in point: In conversation with members of EWS, I've discovered that when it's all said and done, people just want to feel strong, be self-sufficient, and have more time and energy to spend with the people they care about and doing things they love. The best amount is what allows them to stick with it without the pressure to keep doing more.
For anyone who wants the same things, the key is believing/accepting that you're doing enough!
My advice, for what it's worth, to anyone wanting to attain any fitness outcome is to look for what's "good enough" because often there's a lot more satisfaction when you have that filter. If you're only looking for "what's best", then you run the risk of getting trapped in the endless chase of better, which inevitably means "do more" for very little return, especially if your life contains more than just time to work out.
I've seen too many people feel entirely frustrated because they're "doing everything right" but it's still not enough.
The 80/20 of working out is worth finding.