This is very true. Exercise has more of an effect than the calories burned. It improves your health and you feel much better than when you had a sedentary life. As always the answer is that decreasing calorie consumption with moderate exercise is key to maintaining weight loss.

Just as exercising cannot offset massive overconsumption of food, massive underconsumption of food will make one that is dieting feel terrible, and thus not as likely to continue.

In addition the amount of exercise done is never going to really offset a sedentary job. Someone walking on their feet all day vs me being at a desk is going to consume much more energy than me even if I workout after work intensely for an hour. So I am still going to need to consume less than them. But if I did not do the hour of exercise, my body would break down from not being used, and my overall feeling of health would decline.