Does Muscle Weigh More Than Fat?

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Ever start a workout program only to find the scale doesn’t budge (or actually goes up)? Both cardiovascular exercise and resistance training can build muscle and reduce fat, so just because the pounds don’t change doesn’t mean all that exercise is going to waste [1] [2]. And because muscle has a much greater density (it takes up less volume than an equal mass of fat), it’s possible to get visibly slimmer without a significant drop in weight [3].

Does This Fat Make Me Look Fat? — Why It Matters

A common fitness misconception is that a pound of muscle weighs more than a pound of fat. False! — a pound is a pound (of feathers, glass, Jell-O...you name it). But because a pound of fat takes up about four times the space of muscle tissue, it’s possible to look and feel trimmer even if body weight remains the same [4].

Of course, it’s also possible to weigh the same but look and feel fatter [5]. This is especially evident among the elderly, as muscles tend to shrink with age because damaged muscle cells are repaired at a much slower rate than when they were young (grandma and grandpa do look smaller these days). Plus, with reduced physical activity during the golden years, the ratio of muscle to fat tends to decrease as we get older [6].

So while it’s a myth that muscle “weighs” more than fat, too much body fat can be a contributing factor to serious health conditions like stroke, coronary disease, and diabetes [7] [8] [9]. And though it’s difficult to determine the ideal amount of body fat for each individual, too little fat can also have unhealthy consequences, including reproductive dysfunction in women. Accepting the body’s need for both muscle and fat is important in maintaining overall health and fueling an active lifestyle [10] [11] [12].

Scaling Down the Scale — The Answer/Debate

While the actual number of pounds might not waver after starting an exercise routine, the ratio of muscle to fat may be increasing, contributing to better health and improved overall fitness [1] [2] [15]. So after spending quality time bonding with the treadmill or the weight rack, don’t break off the relationship just because the scale isn’t moving in the “right” direction. It might be time to put the scale aside and instead measure results with a glance in the mirror or a new personal best in the gym.

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Photo by Marissa Angell

Originally published on August 30, 2011. Updated October 2013. 

Works Cited

  1. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Garber CE., Blissmer B., Deschenes MR., et al. Medicine and Science in Sports Exercise. 2011 Jul;43(7):1334-59.
  2. Age and aerobic exercise training effects on whole body and muscle protein metabolism. Short KR., Vittone JL., Bigelow ML., et al. Endocrinology Research Unit, Mayo Clinic, Rochester, MN. American Journal of Physiology and Endocrinology Metabolism. 2004 Jan;286(1):E92-101. Epub 2003 Sep 23.
  3. The paradox of low body mass index and high body fat percentage among Chinese, Malays and Indians in Singapore. Deurenberg-Yap M., Schmidt G., van Staveren WA., et al. Department of Nutrition, Ministry of Health, Singapore International Journal of Obesity and Related Metabolic Disorders. 2000 Aug;24(8):1011-7.
  4. Evaluation of anthropometric equations to assess body-composition changes in young women. Friedl KE., Westphal KA., Marchitelli LJ., et al. Occupational Physiology Division, US Army Research Institute of Environmental Medicine, Natick, MA, USA. American Journal of Clinical Nutrition. 2001 Feb;73(2):268-75.
  5. Sensitivity and specificity of the body mass index for the diagnosis of overweight/obesity in elderly. Vasconcelos Fde A., Cordeiro BA., Rech CR., et al. Departamento de Nutrição, Universidade Federal de Santa Catarina, Florianópolis, Brasil. Cadernos Saude Publica. 2010 Aug;26(8):1519-27.
  6. Age-related sarcopenia in humans is associated with reduced synthetic rates of specific muscle proteins. Proctor DN, Balagopal P, Nair KS. Endocrine Research Unit, Mayo Clinic and Foundation, Rochester, MN. The Journal of Nutrition. 1998 Feb;128(2 Suppl):351S-355S.
  7. Measures of Abdominal Adiposity and the Risk of Stroke: The MOnica Risk, Genetics, Archiving and Monograph (MORGAM) Study. Bodenant M., Kuulasmaa K., Wagner A., et al. From the Institut Pasteur de Lille and the Department of Neurology, Univ Lille Nord de France, Lille, France. Stroke A Journal of Cerebral Circulation. 2011 Aug 11. [Epub ahead of print].
  8. Microvascular responsiveness in obesity - implications for therapeutic intervention: 'Review'. Bagi Z., Feher A., Cassuto J.. Department of Pharmacology, University of Oxford, UK and Department of Physiology, New York Medical College, Valhalla, New York, USA. British Journal of Pharmacology. 2011 Jul 28. doi: 10.1111/j.1476-5381.2011.01606.x. [Epub ahead of print].
  9. Insulin resistance with aging: effects of diet and exercise. Ryan AS. Division of Gerontology, Baltimore Veterans Affairs Medical Center, Maryland 21201, USA. Sports Medicine. 2000 Nov;30(5):327-46.
  10. Keeping the young-elderly healthy: is it too late to improve our health through nutrition. Rivlin RS. Anne Fisher Nutrition Center, Strang Cancer Research Laboratory, New York, NY, USA. American Journal of Clinical Nutrition. 2007 Nov;86(5):1572S-6S.
  11. Insulin resistance with aging: effects of diet and exercise. Ryan AS. Division of Gerontology, Baltimore Veterans Affairs Medical Center, Maryland 21201, USA. Sports Medicine. 2000 Nov;30(5):327-46.
  12. Fat mass is inversely associated with serum carboxymethyl-lysine, an advanced glycation end product, in adults. Semba RD., Arab L., Sun K., et al. Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD. Journal of Nutrition. 2011 Sep;141(9):1726-30. Epub 2011 Jul 20.
  13. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Garber CE., Blissmer B., Deschenes MR., et al. Medicine and Science in Sports Exercise. 2011 Jul;43(7):1334-59.
  14. Age and aerobic exercise training effects on whole body and muscle protein metabolism. Short KR., Vittone JL., Bigelow ML., et al. Endocrinology Research Unit, Mayo Clinic, Rochester, MN. American Journal of Physiology and Endocrinology Metabolism. 2004 Jan;286(1):E92-101. Epub 2003 Sep 23.
  15. Aerobic exercise training-induced reductions in abdominal fat and glucose-stimulated insulin responses in middle-aged and older men. Pratley RE., Hagberg JM., Dengel DR., et al. Department of Medicine, University of Maryland School of Medicine, and Geriatrics Service/GRECC, Baltimore Veterans Administration Medical Center, USA. Journal of American Geriatric Society. 2000 Sep;48(9):1055-61.

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