Is counting calories really neccessary?

[dubmaster07]

Now im trying to lose like 25 pounds, so i'm not really obese. I was just wondering if i really HAVE to count calories, do you think i could just eat cleaner and in smaller portions throughout the day while doing HIIT cardio and resistnace training? (weights), my trainer told me that counting calories is only really necessary for more serious weight problems but i want clarification that i can still lose the weight effectively