This is a question I get asked regularly, especially when I am speaking with a client to establish a routine forward. Of course there is no black and white answer but I'll try to offer some more solid suggestions in this short write up.
From my personal experience someone would require 3-5 hours per week of at least moderate activity to make transformative or at the very least significant progress.
This does not mean 3-5 hours with a personal trainer. Some of this time may be doing a preferred sport or hobby such as climbing, swimming or a spin class at the gym.
Dependant on goal, I would typically recommend that at the least 2 of these hours being strength focused. Therefore if you were to engage in the minimum 2 hours per week, then I'd suggest this be strength based.
Now lets look beyond my advice and see how the general NHS guidance compares. The NHS suggests the aim should be to be physically active every day. This is sound advice. I usually suggest to my clients to aim to get 10,000 steps in per day minimum.
The NHS also suggest strength training on at least two days per week.
In conclusion I would suggest 3-5 hours per week exercising, not including the time spent each day walking - or rolling a wheelchair if wheelchair based.
Below I've suggested several examples of a typical weekly routine for a 40 year old man or woman looking to reduce body fat from 22% body fat to 16% bodyfat within 4 months;
Example Week A:
2 hours Personal Training
1 hour independent training based on my suggested home program
2 x 40 minute yoga class
30 minute run
Example Week B:
3 hours Personal Training
40 minute spin class
Example Week C:
1 hour Personal Training
1 hour independent training based on my suggested home program
2 hours power walking
Example Week D:
4 hours Personal Training
Example Week E:
1 hour Personal Training
2 hours independent gym training
2 x 30 minutes jogging
Example Week F:
2 hours Personal Training
2 hours independent gym training
Stay active every day, move when you can, and push yourself, safely.