Why Bother Calculating TDEE?

Why Bother Calculating TDEE?

Everywhere you look it seems like someone is advocating the calculation of TDEE (Total Daily Energy Expenditure) as an effective way to to determine how much you should consume on a daily basis. The idea is that if you consume less than your TDEE then you will lose weight. Conversely, if you consume more than your TDEE then you will gain weight. Read on to find out why TDEE calculations and this way of thinking is NOT an effective way to determine how many daily calories you should actually consume.

TDEE is calculated by finding your Basal Metabolic Rate (BMR) and then adding in any additional energy expenditure. There are several different ways to calculate TDEE because there are several different formulas for calculating BMR [1][2][3]. Which one is correct? None of them!

The best you can hope for with any TDEE calculation is a ballpark estimation. Why? Because all of the available BMR formulas are simple equations which don't account for every factor in the human body that determines actual energy expenditure. They are therefore all rough ballpark estimates. And anyone who has ever tried to base their diet off of a TDEE calculation can tell you, that ballpark can be huge.

Considerations Not Accounted For in TDEE Calculations

Some considerations that are left out of TDEE calculations and that should be taken into account when trying to determine an appropriate caloric intake are:

• Metabolic Damage - long periods of low caloric intake and or high energy expenditure can depress the metabolism, greatly skewing actual TDEE[4]
• Specialized Diets - ketogenic diets, low carbohydrate diets, or other factors can change insulin sensitivity and greatly change the acceptable amount of carbohydrates that can be consumed without weight gain
• Reverse Diets - long periods of Reverse Dieting seem to have a positive impact on the metabolism, but can also skew actual TDEE away from any calculated TDEE

The above factors along with hormonal variations, and other differences between individuals can make for a wide gap between actual TDEE and calculated TDEE.

A Better Alternative to TDEE Calculations

So, if TDEE calculations aren't the best way to determine an appropriate caloric intake then what is?

The best way to determine your actual caloric requirements are to base them off of your current intake and activity. In short, keep your activity constant for a week and track your diet. If your weight increases, then you are likely on a caloric surplus (i.e. you are consuming more calories than you are expending). If your weight decreases, then you likely are on a caloric defecit (i.e. you are consuming fewer calories then you are expending). The delta (the difference in your weight over the week, for you math majors) multiplied by 3500 is your approximate caloric deficit or surplus.

In practice, the above method for calculating caloric requirements works much better than a generic TDEE calculation. And once you have a good approximation of your caloric requirements then you can determine your strategy for either cutting fat or building muscle. Or if you are happy just maintaining your existing weight then you'll know what you need to consume to do that too.

References

[1] Katch, Frank, Victor L. Katch, and William D. McArdle. "Exercise Physiology: Energy, Nutrition, and Human Performance, 1986." Philadelphia, Lea & Febiger.

[2] Harris, J. Arthur, and Francis G. Benedict. "A biometric study of human basal metabolism." Proceedings of the National Academy of Sciences of the United States of America 4.12 (1918): 370.

[3] Mifflin, M. D., et al. "A new predictive equation for resting energy expenditure in healthy individuals.. A reappraisal of the caloric requirements of men." Am J Clin Nutr 46 (1987): 875-885.

[4] Trexler, E., A. Smith-Ryan, and L. Norton. "Metabolic adaptation to weight loss: implications for the athlete." J Int Soc Sport Nutr 11 (2014): 7.

Posted by Clayton Long