If you want to lose weight, diet and exercise are both important. However, that doesn't mean they're equally important. This video explains why changing your diet has a bigger effect on your weight loss than exercise. As we've discussed at length before, most of the kilojoules you burn in a given day are spent just keeping you alive. While you can burn calories through exercise, you don't burn that much. The video above explains that running for 20 minutes only burns around 200 calories or so (837kJ). Whereas an average 600ml bottle of Coke contains 260 calories (1080kJ). If you could choose to get rid of 200 calories by working out for a half hour, or drinking water with dinner, which do you think would be easier?
The video goes on to explain that exercise is by no means bad. There are plenty of other health benefits to exercise that have nothing to do with weight loss. However, if your goal is to lose weight, quantifying how much you're eating in a given day will be a better first step than hitting the gym after that burger.