I don't pay attention to my calories. Some days I eat all day and some days I eat barely anything. I just eat when I'm hungry. I think everyone is different and you have to figure out what works best for you.

There seems to be a self-regulation mechanism built into a diet providing adequate fat & nutrition. A lot of people start out thinking they'll eat half a cow everyday if they don't track, and many do for a few days, and then their body suddenly realizes that they don't need to eat that much every single day if they're getting it constantly. If you're willing to do some hunting, look for the threads from the April challenge. They hid their calories to see what would happen.

It's more complicated than just simply counting what you eat and making sure you don't go over a number. Most importantly, the calories-out side of the equation is dynamic, unpredictable, and is often changed by the calories-in side. If you're eating an amount that causes your weight to stay the same (CI = CO), then you would assume that eating less would mean you start losing weight. This is not necessarily true, especially when your body's metabolism is functioning correctly. To some degree, when you lower CI, CO can (and will) also lower to compensate. Likewise, if you were balanced and added extra calories every day, you won't necessarily start gaining weight. Your calories-out will rise to make up for it.

Calories doesn't really tell you much useful. Scale trends and scale averages are a little more useful. If you're losing weight, you're eating fewer calories than you are burning. If you're gaining weight, you're eating more calories than you are burning. How much fewer? How much more? It's impossible to be sure. Will dropping 500 calories off your current amount cause you to lose an extra pound each week? It's impossible to be sure. Will adding 500 calories to your current amount, slow your loss or cause you to gain by a pound a week? Again, only experience will tell you for sure.

My experience is that eating extra, and I mean a lot extra, can cause me to stop losing weight. If I really push myself to eat a lot, it can cause some gain. But, not as much as I would predict. Eating as much as I want causes me to lose fairly steadily (slower now than I am so close to my goal). Eating less than I would otherwise want will speed things up, but not as much as you would predict. I might lower my calories 500/day, but it usually won't represent an extra pound a week. It might be a quarter pound or a half pound a week. The real difference is the amount of misery I am in, eating fewer calories than my body desires.

Here is a pretty good self-experiment a guy did about trying to gain weight on a low-carb and high-fat diet. In the end, he did gain weight, but not nearly as much as predicted. When he later did it was high-carb and low-fat (same calories), he does end up gaining. http://live.smashthefat.com/why-i-didnt-get-fat/

There are lots of theories about how this stuff works, but when they put people under controlled conditions and measure stuff like thermogenesis and exhaust gasses, they find it's mostly about calories. People lose about the same amount of weight on low-fat diets as on low-carb diets, for example, if they consume the same amount of calories. But they find that people on low-carb diets spontaneously consume less.

There is a proven thermogenic effect due to protein consumption. There is also a hypothetical thermogenic effect due to ketosis, but it has not yet been oberved in a controlled environment.

I did Atkins about 3 years ago...never counted calories, just carbs...stayed between 20-30 net carbs daily and lost about 30lbs in 6 months. I fell off the wagon, gained everything back and then some and just started LC again and using MFP for the first time...I'm watching both my calories and my carbs, but I'm realizing that I ebb and flow. I'm only 3 weeks in, but I'm down 10lbs total...some days I've gone over both calories & carbs and other days I'm below. I figure overall I'm eating healthier and feeling better and have steadily been losing, so I'm happy...even if it's slower.

That's how we can see, through posting on this forum, that we are all different! We all must find OUR sweet spot and what WORKS FOR US!

I must have found your sweet spot and just added it to mine.
If I don't track calories I find myself only eating 800-1000 after a time. No way is that good for me.

I will add, that situation primarily occurs when I am keeping a very tight rein on my protein along with the carbs. So if I want to strictly eat only 80 g of protein a day, that makes for very small serves of food, especially if I'm having a "half protein snack" in there too. I end up with 20g per meal and 10g per snack