Everyone joining a gym has a goal. As with any goal you need to put the work in to help reach it. Most people will do the gym 3,4,5 or even 6 times a week. But where they fail is the nutrition aspect...

Some people will say its 70% nutrition 30% exercise. Others will say its 100% nutrition, 100% exercise. 
The argument is you can still get somewhat of a result without incorporating one or the other. If your looking to lose weight you don't necessarily have to be a member of a gym and attend 6 times a week. If you eat sensibly and are in a calorie deficit you will still be able to lose weight, but it will only be able to take you so far.

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Incorporating nutrition and exercise together will both work faster than anything to help get you to your goal. If you're only attending the gym and training 3 times a week, and eating whatever you like that result will only get you so far.

Again, if your eating sensibly and are within a calorie deficit but not exercising this will only get you so far.
 You don't need to go all out on your exercise or nutrition despite what people say, make small changes to each aspect as and when you need too.