The 1,200 Calorie Myth

The other day I encountered another poor soul led to believe that she must eat 1,200 calories per day in order to lose weight. After explaining why she was incorrect and how she'd been misled by the internet, I decided it was time to see how many cases actually line up with 1,200 calorie diets. Before I dive into the math behind this, I freely admit there are exceptions to every rule in fitness. The odds of someone being one of the exceptions is very small.

Weight loss can be simplified to a single statement, "eat fewer calories than you burn." Whether you perform exercise to raise your caloric burn level or you reduce your intake, weight loss occurs at a deficit. The bad news is that too big of a deficit results in muscle loss, hormonal damage, and metabolic slowdown. The end result is making weight loss harder. There are always exceptions in health and fitness, but chances are, needing 1,200 calories to lose weight isn't because of their body, but because of what they have done to their body.

It is suggested that the caloric deficit not exceed 500 calories below maintenance. Under the assumption that one must eat 1,200 calories to lose weight, that would mean the number of calories needed for maintenance is 1,200 + 500 = 1,700. With the simple multipliers used to convert RMR into TDEE, we can determine the corresponding RMR's.  The following table displays the five measures of activity along with the corresponding RMR that matches a TDEE of 1,700.

Activity	Multiplier	Calories
Sedentary	1.2	1,417
Light	1.3	1,308
Moderate	1.55	1,097
Heavy	1.625	1,046
Very Heavy	1.9	895

This simple analysis gives us two cases where 1,200 calories is below RMR. This is exquisitely bad over a long period of time as it is typically not sustainable, slows metabolism, slows growth and repair of tissue, and negatively effects hormone levels. The remaining three demonstrate an RMR highly unlikely to be found by anybody working out at the required level to reach a TDEE of 1,700.

In order to test large amounts of hypothetical data, I created a program to calculate RMR and BMI based on a set of conditions. The program was run with the following limitations:

Age: 18 - 64
Height: 4'11" - 6'0"
Weight: 103 -250 pounds

The test program reported no instances of a sub 1000 calorie RMR that would not be considered "Underweight." Further, of the 97,384 potential combinations based on the restrictions, there are 8% (7,703) cases of RMR between 1,000 and 1,200, with approximately 2% having a BMI classified as "Overweight" and .05% considered "Obese." Of those 2,030 cases, all of them are under 5'4" and older than 34 with the "Obese" starting at age 54. The lightest bodyweight meeting these qualifications is 129 pounds for a 4'11", 34 year old ranging up to a 146 pound, 5'4", 64 year old. If we look at RMR from each factor, RMR decreases with age and increases with weight. As weight typically increases with height, it can be seen that as height increases, so does RMR.

Again, the chances that the average female looking to lose weight falls into "1,200 calorie diet" are very slim.

As the calculations found, there are some exceptions to the "1,200 calories is not for you" rule, but chances are you aren't one of them. One exception is the person that has already damaged their metabolism by chronically under-eating. This metabolic slowdown may result in needing to eat 1,200 calories, but through proper diet, this can be reversed back to a more sustainable level. Another exception would be someone on a prescription medicine that impairs metabolic rate. The only other exception I will mention is under the direct care of a medical professional and they will have very specific reasons and guidelines for using the 1,200 calorie diet.

How Can I See Where I Am?

First, we need to find our RMR. From there, we can find our TDEE. Many calculators refer to BMR which is a very strict hospital monitored  measurement of the RMR and is typically slightly lower than RMR formulas estimate. In my opinion, BMR is not relevant unless you literally sit in bed and do absolutely nothing all day. While no formula is perfect for everybody, there are two that have the best RMR predictions for the largest population. Mifflin-St Jeor is the most recent formula developed and demonstrated a greater accuracy than previous formulas. Harris-Benedict is the second formula and is still used by many of the online calculators. In order to calculate the TDEE, the RMR is multiplied by an activity quotient. You can use the Z Strength Calculator to determine your RMR and TDEE and save yourself some time.

Now that we know our minimum (RMR) and maintenance (TDEE), we can create our deficit. The deficit should not force you below your RMR and should be no more than 500 calories below TDEE. I'm willing to bet fewer than five people reading this will calculate 1,200 calories as an appropriate deficit and remain above their RMR. In a perfect world, we would increase the space between our RMR and our TDEE by increasing activity, allowing us to lose weight while eating the most calories possible.

Again, if we eat too far below our TDEE, we risk slowing our metabolism, making it harder to lose weight. When this happens, the standard response is either a) eat less or b) be more active. Both options create a bigger deficit forcing the body to slow metabolism further. Remember, the human body has learned to survive over thousands of years and it will compensate to survive.

Regarding the Program Used to Gather Data

Using the limitations, the program calculated more than 97,000 combinations, finding fewer than 8,000 that resulted in an RMR of 1,200 or lower. In an attempt to relate these numbers to a common factor, it also calculated the BMI (Body Mass Index) for each of the combinations. The majority of these combinations resulted in a BMI below 22, which is well within the "Normal" range. While many of us agree BMI is a bad tool because more muscular people rank as "Overweight" or "Obese", it is a useful tool for the less muscular developing weight loss goals.