How do I have a healthy lifestyle?

A healthy lifestyle is something that definitely can't be forced. You can be successful at it for awhile if you force it, but in a lot of cases, you'll end up back where you started. You can start by taking walks and gradually build it up to a regular exercise routine, after you stick to your exercise routine for awhile, you'll realize some pretty big changes in yourself. You'll naturally have less of an urge to eat stuff like chips and even soft drinks, instead your body will crave healthy stuff like vegetables and water. A diet plan in that sense is not even necessary as you'll be more in tune with your body and you'll naturally be consuming healthier food. But if having a diet plan is a must for you then add the diet in after having stuck to your exercise routine for at least two weeks. Never do it all together or it might be too tough to maintain. A healthier you is a process that should be gradual so that it can be maintained.

Should I eat less?

Really depends on how much you're eating on a daily basis. If you've stayed at the same weight for a period of time, it's really unnecessary to cut your diet to lose body fat. All you have to do is burn more calories than your body absorbs and you're on the right path to weight loss (well actually body fat loss to be accurate). Thats as simple as it is. You might see a gain in weight if you do this, but it's really muscle gain. And more muscle mass means more calories burnt even when you're not doing much. Of course the fastest way to lose body fat is to combine exercise with dieting. But I for one love food too much to do that. However, if you intend to exercise while dieting, do keep some things in mind. When you've just started an exercise routine, give it some time before starting dieting as well. Your body is already under additional stress from working out. You don't want to make it work overtime with lousy wages right from the start. Let your body get used to the additional workload, then slowly ease into it.