Whether your goal is a body that looks good, a body that functions well or a body that does both you are probably already aware that either a good diet or regular exercise alone are only half of the deal. Combining good diet with regular exercise is where the magic happens.
If you spend 5 minutes on google searching diet vs exercise you will come across all sorts of percentage claims about which has the biggest impact: 60% diet, 40% exercise; 75% diet, 25% exercise etc but the thing you have to keep in mind is what are you aiming for?
If you simply want to shrink your body in size as quickly as possible then yes, reducing your calories will get you there. I have nothing against focussing on the aesthetic benefits if that is the best way for you to find your motivation to keep in shape and eat well. However, if you take the route of calorie restriction with no exercise you will not simply lose fat you will lose muscle and bone density as well. So, even if you are young enough and vibrant enough to have thus far had no cause to spare a moments thought for your health, not only should you consider that at some point in life (maybe the first time it fails you) you will realise that your health is the most valuable asset you will ever have, but you should also keep in mind that just shrinking your overall size in the fastest way possible may not do much good for how you look either. Yes you can achieve smallness, but you will probably create a body which still has a high percentage of fat, is not firm in the areas you would like it to be, so in fact does not look that great, and on top of that is not strong or resilient, does not have a powerful immune system, lacks energy and may well not look that healthy even if the calories you consume are from nutritious sources (and definitely if your strategy has been to consume rubbish food but just in very small quantities)
However, just as you cannot out diet a lack of exercise you cannot out exercise a poor diet….
If you wish to lose weight doing so through exercise alone is hard. Creating a calorie deficit through your food involves a few smart choices when it comes to avoiding calorie dense foods and/or empty calories. Doing so through exercise requires hours of hard work as each hour of vigourous exercise may burn less calories than a single large piece of cake. Regardless of this there is just never a situation where the one negates the need for the other. Even if you are running marathon distances every week if you then go and fill your body with nonsense, just because calorie-wise and weight-wise you can get away with it you will again fall short of the ultimate goal. You may well end up with bad skin, poor immune function and mood swings. The most likely outcome from eating badly, even if combined with exercise, is that you will struggle to keep a lean figure anyway due to the ease with which calories are taken in through unwise food choices.
If you want it all, a strong, lean body, firm in all the right places, clear skin, good immunity, more emotional stability, better sleep, high energy and a better mood then you must take on board the fact that it is the combination of an active lifestyle and good nutrition that can take you there.
I will spend plenty of time in the future going over ideas for activity and strategies for fitting your exercise in, which foods to be wary of (particularly the devil which is sugar) and which to embrace, but for now just start with the philosophy of mostly good most of the time. Nobody is perfect but if you start by making sure you make more decisions to do things that help your health than things that hinder it you will get yourself on the right path.