BMR and Obesity

Question:

I had a question regarding BMR. I have a 30 year old male client who is obese (355 pounds and 73 inches tall), and I was trying to figure out what his BMR would be so I could give him a range of his daily caloric intake in order to lose weight effectively. I figured out his BMR to be 4222. That would make his range 3220 to 3720 going off of one to two pounds loss a week plus exercise? That seems a little high to me. Are there any considerations or is there a different formula to use to determine an extremely overweight person's BMR? I used the following equation: BMR = 66 + 13.8 x bodyweight (kg) + 5 x height (cm) - 6.8 x age. Multiply that number by 1.2, 1.3, 1.4 or 1.5 depending upon one’s activity rate. If you could help in any way, I would appreciate it.

Answer:

Basal Metabolic Rate (BMR) is considered as being the amount of energy needed to sustain the body in a temperate environment. One of the equations utilized to predict approximate caloric values for BMR was developed in 1914 by J. A. Harris and F.G Benedict. Their formula is still used today by many health and fitness professionals to predict the daily calorie requirements of their clients.

Harris & Benedict Formula (Calories/Day)

• FEMALE BMR= 655.0955 +(9.5634 x weight (KG)) + (1.8496 x height (cm) – (4.6756 * age (years))
• MALE BMR= 66.4730+(13.7516 x weight (KG)) + (5.0033 x height (cm) – (6.7550 * age (years))
• Your client’s data: MALE BMR= 66.4730+(13.7516 x 161KG) + (5.0033 x 185cm) – (6.7550 * 30 years) = 3003 Calories/Day

Alternate Harris & Benedict Formula (kJ/day)

• FEMALE BMR = (40.0 x W(kg)) + (7.7 x H (cm)) – (19.6 x A(years)) + 2.741
• MALE BMR = (57.5 x W(kg)) + (20.9 x H (cm)) – (28.3 x A(years)) + 278
• Your client's data: MALE BMR= (57.5 x 161kg) + (20.9 x 185cm) – (28.3 x 30 years) + 278 = 12553 kJ/day = 3000 Calories/Day

Recently, questions have been raised regarding the tendency of the equation to under estimate the calorie needs for the very muscular and over estimate the calorie needs of the “very fat.” With this in mind, the International Dietary Energy Consultative Group state that the impact of the increased adipose tissue should have little impact on BMR at rest but may have a degree of impact on the amount and energy cost of physical activity.

With activity in mind, to determine the bodies’ Daily Energy Requirement (DER), BMR must be multiplied by the daily Active Metabolic Rate (AMR). AMR refers to the amount of energy the body utilizes for a given activity. AMR is expressed by a numerical value dependent on the nature of the activity with several variations available (an example is shown in Table 1 below).

Table 1

Your client’s data: AMR at 1.4 (Light everyday activities of daily living like standing, cleaning, etc – As I am unsure as to the client’s occupation/daily habits etc) = 4204 Calories/Day

In addition to the formulas used, many health and fitness professionals include Diet Induced Thermogenesis (DIT) (the amount of energy utilized to breakdown/digest food) into the equation, this being approximately 10 percent of the total energy intake.

Your client’s data: DIT = - 420 Calories (10% of 4204). Therefore DER = 3785 Calories/Day

With most experts agreeing that a 300 to 500 calorie deficit with moderate daily exercise is safe for permanent weight loss…

Your client’s data: Calorie restricted DER = 3285 Calories/Day

….fitting right into the range you determined.

Alternate Formulas

As with many numerically represented measures utilizing predictive formulas, there are always other formulas that can be used.

Shofield Formula (MJ/day)

• FEMALE (30-60 years) BMR  = (0.034x W(kg)) + 3.538
• MALE (30-60 years) BMR  = (0.048x W (kg)) +3.653

Owen et al (kcal/day)

• FEMALE RMR = (7.18 x W (kg)) + 795
• MALE RMR = (10.2 x W(kg)) + 875
  RMR = Resting Metabolic Rate is a closely related measure, often interchangeable in articles. Where Basal is considered bare minimum to function, resting is considered as low as it goes in during rest. The difference? Consider a patient in a coma.

Mifflin et al (kcal/day)

• FEMALE   REE = (10 x W(kg)) + (6.25 x H (cm)) – (5 x A (years)) - 161
• MALE    REE = (10 x W(kg)) + (6.25 x H (cm)) – (5 x A (years)) + 5
  REE = Resting Energy Expenditure

Table 2: Formula Comparisons Using Client Data Provided

As can be seen in Table 2, there is a range between lowest and highest predictions (613 Calories). A study by Bauer et al (2004) found that when using the above equations (plus several others which included fat mass), there were little statistical differences when comparing groups, but the differences were clinically significant when considered individually (as shown above).

So in conclusion, regardless of what equation you use, the formulas are just a guide, and the impact of the calorie restrictions must be monitored and adjusted to suit the individual.

References:

1. Bauer, J., Reeves, M.M. & Capra, S. (2004). ‘The Agreement between Measured and Predicted Resting Energy Expenditure in Patients with Patients with Pancreatic Cancer: A Pilot Study’, J Pancreas, 5(1):32-40.
2. Harris, J.A. & Benedict, (1919) A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington, Washington DC.
3. IDECG (1994) Energy and Protein requirements, Proceedings of an IDECG workshop; London School of Hygiene and Tropical Medicine, Pub: United Nations University
4. Mifflin, M.D., St Jeor, S.T., Hill, L.A., Scott, B.J., Daugherty, S.A. & Koy, Y.O. (1990). A new predictive equation for resting energy expenditure in health individuals. Am J Clin Nutr, 51: 241 – 247.
5. Mc Ardle, W.D., Katch, F.I. & Katch, V.I., (1996). Exercise Physiology 4th Edition. Malvern PA: Lea & Febiger.
6. Owen, O.E., Kavle, E., Owen, R.S., Polansky, M., Caprio, S., Mozzoli M. A., et al. (1986). ‘A reappraisal of caloric requirements in health women.’ Am J Clin Nutr, 44: 1 - 19.
7. Owen, O.E., Holup, J.L., D’Alessio, D.A., Craig, E.S., Polanski, M., Smalley, K.J., et al. (1987). ‘A reappraisal of caloric requirements of men.’ Am J Clin Nutr, 46: 875 – 885.
8. Shofield W.N. (1985). ‘Predicting basal metabolic rate, new standards and review of previous works.’ Hum Nutr Clin Nutr, 39: 5 – 41.
9. Wilmore, J.H. & Costill, D.L., (1994) Physiology of Sport and Exercise. Champaign,IL : Human Kinetics.