Fat Loss vs. Fitness
If your major goal is to lose fat, try the 12-week weight loss program. Many programs include effective workout routines, while also addressing the critical aspects of nutrition and sleep in order for you to lose the most weight possible during the program. If your major goal is to reinvigorate your interest in exercise, or you need to break through a plateau in your training, a 30-day fitness challenge will be better. This type of challenge can help improve all aspects of fitness while also helping you develop a sense of community with other people participating.
Building Habits vs. Having Fun
If your goal is fat loss, building good exercise and diet habits is vital. A 12-week weight loss program gives you enough time to settle into a good routine and become used to the lifestyle adjustments necessary for your success. If your goal is to improve your fitness, it's important that your training is varied so that you can maintain your interest in it. That's why a 30-day challenge is more effective for improving fitness -- there is a sense of competition and engagement with the process that will keep you motivated.
Sustainable Progress vs. a Challenge
When fat loss is your focus, it's important that you make sustainable progress over a prolonged period of time. A 12-week weight loss program allows for this, setting you up with the sensible, effective habits that will help you continue losing weight, or maintaining your new weight, once you finish the program. This is why crash diets tend to fail -- they don't help you establish sustainable progress. If your focus is on boosting your fitness or getting out of a rut, a challenge is exactly what you need. 30 days is long enough to have a noticeable impact on your fitness, but is not so long that you lose interest.
Lifestyle vs. Event
When you're determined to lose weight, your whole lifestyle has to align with your goal. All your actions contribute to how successful your weight loss journey is -- getting consistent with exercise and healthy eating is obviously vital, but getting enough sleep and avoiding alcohol are also key. A good 12-week weight loss program will cover this and provide you with a framework to achieve the necessary lifestyle adjustments. A 30-day fitness challenge is more of an event. You don't necessarily have to alter your whole lifestyle to get the fitness benefits from it.