Basal Metabolic Rate
The first thing you need to do is calculate your basal metabolic rate, which is the amount of calories your body burns at rest. Meaning, even if you sat on the couch all day like a lump on a log, your body would still use that many calories each day. There are some fancy scales out there that can determine your BMR more accurately based on your muscle mass and body fat percentages but the Harris-Benedict equation below is generally accepted as a good estimate:
For Women: BMR = 66 + (6.23 x Weight in lbs) + (12.7 x Height in Inches) – (6.76 x age in years)
For Men: BMR = 655 + (4.35 x Weight in lbs) + 4.7 x Height in Inches) – (4.7 x Age in Years)
I am 140lbs, 5’5” tall (65”), and 27 years old so I show a BMR of 1580.
To determine the number of calories needed to maintain your current weight, you should multiply your BMR by one of the following factors:
Little or No exercise: x 1.2
Light Exercise (1-3 days/week): x 1.375
Moderate Exercise (3-5 days/week): x 1.55
Heavy Exercise (6-7 days/week): x 1.725
Very Heavy Exercise (twice/day, intense workouts): x 1.9
For me, I prefer to assume little or no exercise for my base diet and then I can choose to add extra calories based on how much I am working out. That way on the days I don’t work out I don’t overeat. So if you take my BMR of 1580 and multiply by 1.2 for little to no exercise you end up with 1900 calories per day to maintain my current weight.
Now, if you want to lose weight, you either need to burn more calories by exercising or you need to consume less calories. I like to try to do a mix of both by planning my diet to lose 1lb per week. Note: I often don’t lose 1lb each week, sometimes it’s because I have gained muscle mass from my workouts that doesn’t show up on my scale even though I lost fat, and sometimes it’s because if you keep track of the whole week carefully, you may not have done as well as you thought on your diet or exercise. To lose 1lb of fat, you need a calorie deficit of 3500 calories (kcal). That means that if you want to lose 1lb of fat per week from dieting, you need to decrease your daily maintenance calories by 500 (3500 calories per week / 7 days = 500 calories per day less than usual).
1900 Calories to maintain current weight – 500 calories to lose fat = 1400 calories per day.
That would be your new target calories for the day. I did some more research and it did show that the average recommended calorie intake for women trying to safely lose weight is between 1200 – 1500 calories. I tend to do well on the weekdays but slip up on the weekends so even though my diet said I should be able to lose the weight at 1400 calories, I have been aiming for 1200 so that if I go over sometimes, it shouldn’t wreck my diet completely but if you are feeling constantly hungry then you are either not getting enough calories or not getting the right balance of calories. Keep in mind, that I will often add calories if I am working out – this is my base diet on a normal day that I don’t have any intense workouts.
The next thing you need to do is determine the target number of calories and balance of proteins, carbs and fats that you want in your diet. For me, I like a balanced diet where 40% of my calories are from Protein, 30% are from Carbs and 30% are from Fats. There are lots of different theories on the size of each meal so you can break these up however you choose. Below is a summary of how my diet works out based on 1200 calories per day with a 40/30/30 balance:
1 gram of Protein = 4 calories
1 gram of Carbohydrates = 4 calories
1 g of Fat = 9 calories
Let’s use my dinner as an example:
First I figured out the calorie breakdown. Once I decided that I wanted my dinner to be around 450 calories, then you can figure out the grams of each needed.
450 calories x 0.4 (40% Protein) = 180 Calories from protein / 4 calories per gram protein = 45g of protein
450 calories x 0.3 (30% Carbs) = 135 Calories from Carbs / 4 calories per gram carbs = 34g of carbohydrates
450 calories x 0.3 (30% fats) = 135 Calories from Fat / 9 calories per gram fat = 15g of fat
That’s how I figured out the targets for each of my meals. Now, there is one more VERY important tip Bonnie gave me that is working out wonderfully. Rather than pulling your hair out trying to check every meal for the proper balance of protein, carbs and fat, if you just make sure that the meal is the proper number of calories and has enough protein (or as close as you can get), the carbs and fats usually work out to be pretty close to what you wanted. So you don’t have to worry about watching carbs and fats! Isn’t that helpful?
For the days that I have a small work out, like a 20 – 30 minute run, I usually don’t add any extra calories unless I feel hungry or fatigued later in the day because that only burns a couple hundred calories. But if I do a bootcamp, sprints/intervals workout, or other high intensity workout that will burn 500+ calories, then I usually add a pre-workout snack of around 150 calories (my favorite is half a whole wheat English muffin with a tbsp of peanut butter) and sometimes a small post snack to get the glycogen back to my muscles (like a “protein-to-go” drink mix, or whey protein and honey). Like I said, it’s all based on calories in versus calories out and a 3500 calorie deficit equals one pound of fat. So if you aren’t dieting, it could take 7 high intensity workouts just to burn one pound of fat!
To keep track of your calories in versus calories out, there are a ton of apps out there that you can access via your smartphone or the internet. A lot of people like My Fitness Pal, Lose It! and Calorie Counter. Lose It! definitely has the best user interface that makes it easy to see if you are getting the proper ratio of protein/carbs/fats and whether you are over/under on your calories AND it will integrate with RunKeeper if you upgrade to the premium service instead of the free one. However, calorie counter seems to have a better search function when adding ingredients or meals. I think I’ll stick to Calorie Counter for now but let me know if you have any other favorite apps I should try out!
*****PLEASE REMEMBER: I am not a doctor or a registered dietician, just an average person making nutritional decisions based on advice from personal trainers and nutritionists combined with research and experience of what has or has not worked for me.*****