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Myth: Weight Training will significantly increase your basal metabolic rate.

Does adding muscle actually increase REE in a clinically significant way? In a presentation Dr. Stephen Heymsfield (Professor of Medicine at Columbia University; researcher at St. Lukes-Roosevelt Obesity Research Center) gave in 1996 he pointed out that the idea that skeletal muscle has a high REE is false, and that where the idea got started is unclear. While skeletal muscle and adipose tissue are the two largest fractions of body weight, their contribution to REE is considerably smaller than that of organs (see Table).(1)

John Jakicic PhD, Director of the University of Pittsburgh Physical Activity and Weight Management Research Center and Dixie Sanforth MS, kinesiology lecturer at the University of Texas) presenting at the American College of Sports Medicine’s 2003 spring conference made similar points: while strength training has many benefits a clinically significant increase in REE isn’t one of them, and that we need to be careful to be accurate when conveying those benefits.

Table:  Lean Body Mass Contribution to REE

 

% Body Wt.

% REE

 

Organs

5-6

60-70

 

Skeletal Muscle

30-40

16-22

 

Source: Elia (2)

Leading researchers in this area believe that the best data we have on tissue metabolism indicates that the REE of skeletal muscle is just 13-kcals/Kg per day, while organs (heart, kidneys, liver and brain) have the highest REE (200- to 400 kcal/Kg per day). Adipose tissue adds just 4.5 kcals/Kg per day to REE.(2)

According to Dr. Jakicic, he has yet to see clinical data supporting the notion that increasing skeletal muscle mass has a clinically significant effect on REE. It seems that the literature on this topic is wrought with methodological problems and conclusions not supported by the data they’re "based on." A meta-analysis of 22 studies found “no relationship between changes in REE and changes in FFM across studies.”(3) The Energy chapter from the National Academy of Sciences 2002 DRI’s discusses several similar points.(4)

Based on the above noted REE for skeletal muscle and adipose tissue, a client who replaced 2 Kg of adipose tissue with skeletal muscle would have a net increase in REE of just 17 kcals per day. A review of 45 studies on the effect of exercise on body composition (studies averaged 130 minutes per week of aerobic, strength or both activities) found that the average subject improved their body composition by ~1.4%, which consisted of changes in LBM and fat mass which were significantly less than 2 Kg each. While there was no difference in the overall change in body composition between activity types, the result was achieved by greater fat loss secondary to aerobic activities and greater LBM gain secondary to strength training. The reviewer concluded that, “formal exercise training in the absence of significant changes in diet does not result in substantial changes in body weight and body composition.”  It should be noted that the average weekly “dose” of activity in this review is far less than the latest recommendation of one hour of accumulated physical activity per week for the maintenance of a healthy body weight.(4)

It’s important to note that REE falls an average of 1% and 0.8% per decade in men and women respectively. This reduction in REE is equivalent to the loss of ~1.5- to 2 pounds of LBM per year. While strength training is unlikely to have a clinically significant affect on REE over the short term, it can prevent the ongoing loss of LBM, and is likely to prevent much of the typical decline seen in REE as subjects age.

1. Wang Z, Heshka S, Zhang K, Boozer CN, Heymsfield SB: Resting Energy Expenditure: Systematic Organization and Critique of Prediction Methods. Obes Research. 2001;9:331-5.

2. Elia M: Organ and Tissue Contribution to Metabolic Rate, in "Kinney J, Tucker H (eds). Energy Metabolism: Tissue Determinants and Cellular Corollaries. New York, NY: Raven Press, Ltd.; 1992:61-77.

3. Thompson JL, Manore MM, Thomas JR. Effects of Diet and Diet-Plus-Exercise Programs on Resting Metabolic Rate: A Meta-Analysis. Intl J Sport Nutr. 1996;6:41-61.

4. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Food and Nutrition Board. Washington DC: National Academy Press; 2002.