Counting calories - Where to start?

I first want to say that I do not religiously count calories. I do not track every bite I take in myfitnesspal.com or any other calorie tracking program. However, over the past six months I've taken a much greater interest in the number of calories in my food, along with the amount of fat, carbs, proteins, vitamins and other content. While I refuse to obsess over the caloric content of every bit of food that crosses my lips, I think it's useful to know how many calories I should consume to maintain, and how many I should consume to lose. I'm currently trying to maintain my weight (over the summer), but come fall I want to lose the last 3-5 pounds, so I'll need to be more careful.

So, to figure out my baseline, I've used the Harris Benedict-Equation, which determines a target caloric intake based on your Basal Metabolic Rate (BMR). The Insanity program uses a calculator based on this. BMR is basically the number of calories your body needs to stay alive and healthy. Once the BMR is calculated, you add an "allowance" for physical activity to determine the number of calories you should consume to maintain your current weight. From this number, determine a healthy caloric deficit based on your weight loss goals (this will vary greatly from person to person; you may want to chat with your doctor to determine the right level for you).

As a rough estimate, healthy weight loss is approximately 1-2 pounds a week, requiring a caloric deficit of around 3,500 calories to lose one pound. So, a deficit of 500 calories a day is probably a reasonable target if you're trying to lose weight. Like I've said in the past, I'm entirely opposed to diets. For me, it's all about eating healthy food in the right amounts, and permanently changing your approach to food.

THE HARRIS-BENEDICT EQUATION:

1. Calculate your BMR:

        Women: BMR = 655 + ( 4.35 x weight in pounds ) + ( 4.7 x height in inches ) - ( 4.7 x age in years )

        Men: BMR = 66 + ( 6.23 x weight in pounds ) + ( 12.7 x height in inches ) - ( 6.8 x age in years )

2. Multiply your BMR by the appropriate activity factor, as follows:

           Sedentary (little or no exercise): BMR x 1.2

           Lightly active (light exercise/sports 1-3 days/week): BMR x 1.375

           Moderately active (moderate exercise/sports 3-5 days/week): BMR x 1.55

           Very active (hard exercise/sports 6-7 days a week): BMR x 1.725

           Extra active (very hard exercise/sports & physical job or 2x training): BMR x 1.9

NOTE: For Insanity, most people choose to apply "Very Active" or "Extra Active". I think that for T25, "Moderately Active" is probably more accurate (though if you do other physical activity during the day, that will bump you to a higher category).

3. Your final number is the approximate number of calories you need each day to maintain your weight. For weight loss, determine the mild to moderate caloric deficit that is right for you.

So in my case:

Female, 148 pounds, 70 inches, age 42: 655 + (4.35 x 148) + (4.7 x 70) - (4.7 x 42)= 1429

Multiply 1429 x 1.55 (moderately active) = 2,215 calories a day to maintain my weight. With this information, I will probably aim for 1,900 over the summer, since I'm basically maintaining until fall (though dropping a pound or two wouldn't be unwelcome!)