I’ll start from the bottom line. The reason why I am not a fan of any version of “Couch to 5K” is because when the training is done and the challenge is over most people think they’ve achieved something and now they can go back to their normal routine. No permanent change was made. They go back to their old habits of poor eating and some sporadic exercising, if any at all. And that, ladies and gentlemen, is why there’s an inherent flaw in these types of challenges that attempt to motivate people to lose weight or get fit.
My philosophy on life is healthy living. It’s not short term or goal specific. It’s every day, from now until the day you die. Every day you need to make good decisions regarding your health, whether it’s what you eat or how you work out – especially if you are trying to lose weight. You need to make a long term commitment to change your life permanently, not just for some challenge that’s going to be over in a few months.
The problem with these challenges is they attempt to promise people quick results which is not something that can be maintained. I’ve written a few articles on this topic already. If you want to lose weight and keep it off, please stay away from these “get skinny and fit quick” schemes. They do not hold up long term and you will wind up with more weight gain in the end. 
Or worse, since you were not used to running (after being on the couch for a long time), this sudden training schedule might result in an injury which will lead you right back to that aforementioned couch. If you are trying to challenge yourself to lose weight, start slow and make small changes that you can stick to forever!
For people who use these challenges to improve their physical fitness and athleticism I understand how you can be attracted to a definitive course with a goal at the end, but again, when this challenge is over will you continue with your workouts? Or will you stop training altogether
? A better approach would be to sign up for a class or join a beginners run club that meets every week and use it as your regular workout. You don’t need to complete a 5K to be fit! It’s way more beneficial if you run consistently a few times a week with smaller mileages than running a 5K and then giving up on running thereafter.
I hope you can see what I’m trying to say here. In order to lead a healthy life, you need to live it every day. 5K should not be the goal. Every day should be your goal. Approach every day as a challenge to make good decisions for your health.