I get asked quite a bit by friends and co-workers about the amount of calories to consume to achieve their various goals. Although this posting looks long, it is actually easy to calculate your needs; I just like adding a lot of rationale behind the steps.
Step 1: BMR
To understand how many calories you need, you first need to figure out how many calories you need to just maintain your current weight at rest. There are several equations that can be used to calculate your energy needs at rest, the basal metabolic rate (BMR).
Now, BMR between individuals can vary. The largest cause of variation is the amount of lean mass an individual has (Johnstone, Alexandra M; Murison, Sandra D; Duncan, Jackie S; Rance, Kellie A; Speakman, John R; Koh, YO (2005). “Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine”. American Journal of Clinical Nutrition 82 (5): 941–948. http://www.ncbi.nlm.nih.gov/pubmed/16280423). So, all the BMR calculations should be considered as educated guesses. Do not let the math scare you; there are many on-line sites that will do the calculations for you.
This is a newer equation that many believe is a little more accurate than the other equations out there (Frankenfield D, Roth-Yousey L, Compher C. “Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review.” J Am Diet Assoc. 2005 May;105(5):775-89. http://www.ncbi.nlm.nih.gov/pubmed/15883556). Sites like myfitnesspal use this newer equation for BMR calculations (http://www.myfitnesspal.com/tools/bmr-calculator). The advantage to this formula is that you do not need an accurate body fat measurement.
Men: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5
Women: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161
Originally created in 1919 and revised in 1984, the Harris-Benedict is one of the oldest formulas used to calculate calories needed. As such, you will see this equation referenced often. Like the Mifflin-St Jeor equation, the advantage to this formula is that you do not need an accurate body fat measurement.
Men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age in years)
Women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) – (4.330 x age in years)
If you know your lean body mass, this equation involves less math. The problem for most people is getting an accurate body fat measurement – electronic scales have large variations when estimating body fat, for example.
BMR = 370 + (21.6 x lean body mass in kg)
Example: Let’s take a guy who is 6’, 200 lbs, 15% bf, 30 years old. Using the Mifflin-St Jeor equation will yield a BMR of 1907 calories. The other two will calculate a BMR around 2030 calories. Again, this is why these equations are just a starting point that may require a little fine tuning based on your unique situation.
Step 2: TDEE
After calculating BMR, the second step is to multiply it by an activity factor in order to get the number of calories needed to maintain current weight factoring in the number of calories burned doing daily activities (TDEE, total daily energy expenditure). There are several variations on what the multipliers are, but this table shows the common activity factor multipliers. Be honest here on actual workout activity level.
|Little to no exercise||TDEE = BMR x 1.2|
|Light exercise (1-3 days/week)||TDEE = BMR x 1.375|
|Moderate exercise (4-5 days/week)||TDEE = BMR x 1.55|
|Heavy/intense exercise (6-7 days/week)||TDEE = BMR x 1.725|
|Very heavy exercise (2x/day)||TDEE = BMR x 1.9|
Continuing with our example, our example guy’s BMR was calculated to be 1907 calories. If he, on an average week, exercises moderately, his TDEE would be 1907 calories x 1.55 = 2956 calories/day. This value is the number of calories required to maintain current weight.
Step 3: Goal
Now, the calories need to be adjusted by the person’s individual fitness goals are. Calories need to be added for those looking to gain muscle; calories need to be subtracted for those wanting to lose fat. If looking to gain muscle, multiple the TDEE by 1.1 (2956 x 1.1 = 3252 calories using our example). If looking to lose weight, multiply the TDEE by 0.85 (2956 x 0.85 = 2513 calories using our example). Adding 10% for muscle game or subtracting 15% for fat loss is not too aggressive, which is why I suggested these numbers to start with. Adding too many calories when trying to gain weight will likely yield more fat gain than muscle gain. Removing too many calories for those dieting runs the risk of burning muscle. Safe weight loss is considered to be about 1-2 lbs/week.
Now, you know how many calories you need to achieve your goals. As mentioned at the start, this is a really a guestimate – it should be fairly close. You may need to tweak them (i.e. if you calculated a maintenance amount, but either lost or gained weight, you can adjust accordingly).
Step 4: Your Macros
The last step is to break out the macros (protein, carbohydrates, and fat) you need to consume. For each gram, protein and carbs each is 4 calories; each gram of fat is 9 calories.
There are numerous opinions out there on protein requirements. For protein needs, many bodybuilding and fitness websites and magazines promote taking anywhere from 1g to 2g of protein per pound of weight. However, most recent studies conclude that intake of protein above 0.64-0.82g/lb provides no additional benefit for adding muscle. In looking at athletes specifically, 0.82g/lb is the upper limit at which protein intake benefits muscle gain, although high frequency/intensity training may require a little more (Stuart M. Phillips & Luc J.C. Van Loon (2011): “Dietary protein for athletes: From requirements to optimum adaptation,” Journal of Sports Sciences, 29:sup1, S29-S38. http://www.ncbi.nlm.nih.gov/pubmed/22150425). Other studies suggest those dieting may go up to 0.9g/lb in order to spare destroying muscle in a calorie deficit. Realize that if you follow some pro bodybuilder’s diet that many of them do take sizable amounts of performance enhancing drugs that may allow them to use higher protein amounts.
So, if you are working out, the upper amount of protein you will need is going to be somewhere between 0.64 and 0.9 depending on goals. Going back to our example, the TDEE for our subject was calculated to be 3252 calories each day to gain weight. Given he weighed 200 lbs, his protein needs will be 164g using the 0.82/lb finding above (200 x 0.82 = 164). Each gram of protein has 4 calories, so 164g x 4 calories/g = 656 calories each day from protein (percentage-wise, 656 / 3252 = 20%). If we use the weight loss scenario from our example, his protein needs would be 180g day using the 0.9/lb recommendation for fat loss (200 x 0.9 = 180). Since he is consuming less calories (2513), protein is now 29% of his daily caloric intake.
For fat, again there is a lot of opinions on this. Some personal training certification programs teach fat intake should be about 25% of calories; other common recommendations are anywhere from 20% to 30%. If you use 0.4g/lb, that will be close. From our example, the fat needs will be 200 x 0.4 = 80g or 80g x 9 calories = 720 calories each day (720 / 3252 = 22% for the gain scenario and 720 / 2513 = 29% for the loss scenario).
At this point, the left over calories are allocated to carbs. In our weight gain example, 656 + 720 = 1376 calories came from protein and fats. So, 3252 – 1376 = 1876 calories allocated for carbs (1876 / 4 calories/g = 469g carbs) each day. For the weight loss scenario, 1440 calories come from protein and fat. So, 2513 – 1440 = 1073 calories or 268g carbs per day.
That is it. At this point, you have your protein, carb, and fat targets. You can plug these numbers into sites like myfitnesspal.com and track your macros during the day to see how you are doing towards your daily intake. For those trying to gain weight, eating a large amount of calories each day is tough to do in three meals. Typically, most weight gain programs will divide the macros over 4-6 meals/day to make consuming everything more manageable.