Track your calories and macronutrients (protein, carbs, and fats) the first few weeks of your fat loss phase. Here's why:
From a qualitative perspective, you'll identify the highest-level habits you can improve to get the ball of fat rolling in the right direction (off your body). From a quantitative perspective, it'll show you how the typical foods and meals you eat impact your average nutrition numbers. You can then adjust portion sizes in order to hit your target fat loss numbers.
It can show you the difference between "health" foods and "fat loss friendly" foods. Yeah, nuts are healthy, but if you're taking in 1000 extra calories a day by nibbling on them, it'll be difficult to consistently get into that calorie deficit necessary for fat loss.
3 Objectivity and Accountability
If you aren't losing fat and are only hitting your target numbers 80% of the time, you need to bump that average up. Fat loss requires discipline and consistency.
4 Fine Tuning
Sometimes subtle shifts are all that's necessary to start the fat loss process, or to keep it progressing. Some people will jump to extremes when it's not necessary. Maybe all you need is to cut your carbs down by 10% to spark some fat loss. By tracking, testing, and assessing, you can do that instead of cutting your calories in half and carbs to zero, then suffering all of the negative metabolic and hormonal consequences of those extremes.
You Don't Have to Do It Forever
The whole point is to teach you enough about nutrition so that you can eat more intuitively while still reaching your physique goals. You'll soon know the numbers of your typical meals and will be able to eyeball portion sizes.