When I had my measurements taken last week, I also had to re-adjust my calorie intake because it changes with my body composition. Because of this, I also had to re-calculate my calorie deficit. If you’ve been trying to lose weight for awhile, you’re probably familiar with this concept. But, a lot of people are either doing it wrong (eating too much or too little calories) or just don’t know how to calculate their calorie deficit at all.
The concept behind the calorie deficit is simple. You figure out how much you need in order to maintain your current weight (this is your maintenance level) then, you reduce the amount of calories that you eat in order to lose weight. In his book, Burn the Fat, Feed the Muscle,” Tom Venuto says that you should have, at most, a calorie deficit of 30% under maintenance level. This would mean that if your maintenance level is 2,000 calories then, you can eat 1,600 calories to lose weight but not less than that because it slows down your metabolic rate if you reduce your calorie intake even further. Take note, that Tom also mentioned 7 reasons to not undereat when you’re dieting and this is only one of them.
Ok, if I haven’t confused you already, let me give you an example of how to calculate your calorie deficit. Keep in mind that a lot of factors affect your maintenance calorie levels but, to simplify the discussion, I will just focus on the formulas.
The first, simple formula is by using multipliers of Total Daily Energy Expenditure (TDEE also known as maintenance level):
- For Fat loss: multiply by 12 to 13 calories per lb. of bodyweight
- Maintenance (TDEE) = 15-16 calories per lb. of bodyweight
- Weight gain = 18 to 20+ calories per lb. of bodyweight
So, if I wanted to lose weight, I would multiply my weight by 12. Let’s say my weight is 117 lbs. My TDEE would be 1,755 calories (117 lbs x 15) so I’d want to eat 1,404 calories (117 lbs x 12) in order to have a calorie deficit. Take note that this formula is suitable only for people who are “average” which means that they are not grossly overweight or thin. Also, it doesn’t take into account the Basal Metabolic Rate (BMR) which can vary greatly among the general population depending on your body composition, height, age, etc.
This leads me to the next discussion: the Harris-Benedict formula. This takes into account the BMR which means that it will apply to the general population and a lot of people can calculate their calorie deficits this way.
Before I proceed, you can download the calculator that I use here:
Calorie Deficit Calculator
Back to the calculation…
Men: BMR = 66 + (13.7 X wt in kg) + (5 X ht in cm) – (6.8 X age in years)
Women: BMR = 655 + (9.6 X wt in kg) + (1.8 X ht in cm) – (4.7 X age in years)
So, if I have the following statistics:
- Weight: 117 lbs = 53.18 kg
- Height: 5’4″ = 162.56 cm
- Age: 27 yrs old
My calculation would look like this:
BMR = 655 + (9.6 X 53.18 kg) + (1.8 X 162.56 cm) – (4.7 X 27) = ~ 1,331 calories
Because my BMR is my calorie expenditure if I didn’t perform any exercise, I have to multiply it to an activity factor depending on how active my lifestyle is or how much exercise I perform in a week.
Based on the following activity factors:
- Sedentary = BMR X 1.2 (no exercise)
- Lightly active = BMR X 1.375 (light exercise 2-3 times a week)
- Mod. active = BMR X 1.55 (moderate exercise 3-5 days a week)
- Very active = BMR X 1.725 (rigorous exercise/sports 6-7 days a week)
- Extr. Active = BMR X 1.9 (rigorous daily exercise/sports & physical job)
So, if I just go to the gym 3 times a week with strength training and intervals, I would multiply my BMR by 1.55 which will give me about 2,063 calories (1,331 calories x 1.55). Now, I just have to figure out what is 30% of 2,063 which is about 619 calories. I would then subtract 619 from 2,063 in order to give me my calorie deficit of 1,444 calories. If I don’t want to lose that much weight, I would reduce the 30% to 20% and so on.
Again, this formula will not apply to people who have extremely low body fat or extremely high body fat (overly obese) but it will be fine for the general population. For the purpose of this post, this should help a lot of people figure out their calorie requirements in order to know their calorie deficit. There is another more specific formula that takes into account the lean body mass when calculating caloric needs but that one deserves a post all by itself.
Here is the file again. I created this for myself and I’m making it available to you in order to make the process a lot easier. Enjoy!
To dowload the file, right click and save as.