How to calculate your nutritional needs like a dietitian would!

Ok so just for fun (because dietitians find this fun)- lets learn how to calculate your nutritional requirements just like a dietitian would!

So theres a basic formula I use in clinic called the Mifflin-St. Jeor equation. To be honest with you, I have no clue how to pronounce that but I swear I didnt just make it up haha! There are a few steps involved- lets simplify it here in 5 steps....

five steps to calculating caloric needs (the in-depth way).

1) you need to know gender, age, height, weight, and activity level
2) you need to convert the weight and ht to kg and cm....multuply ht in inches by 2.54 to get it in cm and then divide weight in lbs by 2.2 to get it in kg. easy peasy. Pause what your doing, do the conversions, and write down those numbers before moving on....

ready?......

ok.....

3) now we calculate the resting metabolic rate- which is the bare minimum calories our bodies need to survive just for our heart to pump and our breathing etc...as in if you laid in bed and did NOTHING, ever, thats how much you need to survive....this is the hard part- the formula looks big and scary but its not. Its just simple math

here it is (FYI this is for adults not children OR the elderly....they get calculated differently)

for a MALE use THIS....
10 X WT (KG) + 6.25 X HT (CM)- 5 X AGE (YEARS) + 5

for a FEMALE use THIS....
10 X WT (KG) + 6.25 X HT (CM)- 5 X AGE (YEARS) - 161

Lets do an example.

Jane smith (just made her up) is a lightly active, 30 year old mom of 2 who works out 30 min a day,  is 5'4", and weighs 160 lbs. She would like to lose some weight.

first....CONVERSIONS...5'4"=64" x 2.54= 162.56cm     160lbs/2.2= 72.7 kg

So all converted, Jane smith  is 162.56 cm and 72.7 kg. Now we can calculate RMR for her.
because she is a female, we will use the female equation-

10 X WT (KG) + 6.25 X HT (CM)- 5 X AGE (YEARS) - 161
10 x 72.7kg + 6.25 x 162.56cm - 5 x 30 - 161
727+1016-150-161=   1432 kcal

So Jane Smiths resting metabolic rate is 1432 kcal (FYI most people just call them calories- us dietitians call them their real name- which is kilo calories- aka- kcal)

BUT thats just how much she needs to survive without moving! shes a mom of 2 AND she works out 30 min a day so she needs more than that!

4)  insert ACTIVITY FACTOR.

I feel that this is where most people go wrong. They like to think they are more active than they really are. So based on the table- some might think- Jane is very active! she has two kids, and she puts her all into her exercise most days of the week! WRONG. I forget the exact definitions, my reference DRI book is at work (love that thing!), but from the top of my head, lightly active if I recall is the equivalence of walking briskly/ jogging a few miles a day and moderately active is equivalent to like 5-8 miles up to extremely active being like Olympic competitors. I would classify Jane as lightly-moderately active based on her physical activity level and I would use maybe 1.4 as a good activity factor to multiply her RMR by. This part is a little subjective but, remember, this whole thing is just an estimate. The only way to know the EXACT numbers is through indirect calorimetry but lets be real here...I've NEVER used that in my 5 years as an RD. We just don't have access to that. So this is the best we can do.

So we know her RMR is 1432, so lets do the math:
1432 x 1.4 =  2004.8 kcal.

DONE!

no. not yet.

Thats how much she needs to MAINTAIN her current weight. But if we recall, she wants to lose some weight! moving on to the last step...

5) to adjust the needs for goals you can either add or subtract 500-100 kcal  per day based on whether the individual wants to lose weight or gain weight! so for Jane, she wants to lose... I think we could safely subtract 600 kcal from her daily requirement for weight loss goals

that would give her a final caloric requirement to meet her goals of ~1400 kcal/ day


now you can take it a step further and calculate her MACRO nutrient requirements!

macronutrients are the big nutrients- the carbs, protein, and fat vs the micronutrients which are the vitamins and minerals. Its just dietitian talk.

So heres a basic guide- for weight loss, I like to use 40% carbs, 30% protein, and 30% fat.

1g carb= 4 kcal
1 g protein = 4 kcal
and 1g fat = 9 kcal

so if we have 1400 kcal, we can multiply that by .4 to give us the total calories from carbs that she needs. that is 560 kcal from carbohydrates. We know that each gram of carbohydrate is 4 kcal so wed divide 560 by 4 and thatd give us our total grams = 140 grams a day. Try to make at least 25 grams of that from fiber for women and 30 grams fiber for men.

For protein- same thing! 1400 x .3 (for the 30% calories from protein), = 420 kcal divided by 4 kcal per gram of protein = 105 g protein per day.

and last but not least- fat! 1400 x .3= 420 kcal divided by 9 kcal/ gram of fat = ~47 g fat/ day.

and that my friends is how it is done lol! complicated as it looks, its really an easy plug n chug calculation.


Now im going to get some rest bc someone kept me up all night (I wont say names but it starts with the letter J and ends with an "acob" and hes a busy little toddler.....oops I said too much...)

happy calorie calculating ya'll!