Obesity Tissue: Composition, Energy Expenditure, and Energy Content in Adult Humans

Obesity (Silver Spring). 2019 Sep;27(9):1472-1481. doi: 10.1002/oby.22557. Epub 2019 Jul 19.


Objective: Chronic positive energy balance leads to obesity, and the "excess" weight is usually described as consisting solely of adipose tissue (AT) or its two components, fat and fat-free mass (nonfat cell mass, extracellular fluid). This study aimed to clarify the nature of "obesity" tissue.

Methods: A total of 333 adults had AT, skin, skeletal muscle, bone, heart, liver, kidney, spleen, brain, and residual mass measured or derived using magnetic resonance imaging and dual-energy x-ray absorptiometry. First, associations between these components and AT were examined by developing multiple regression models. Next, obesity-tissue composition was developed by deriving mean component mass differences between participant groups with normal weight (BMI < 25 kg/m2 ) and those with obesity (BMI > 29.9 kg/m2 ); respective resting energy expenditures and metabolizable energy and protein contents were calculated.

Results: AT significantly predicted organ-tissue mass in 17 of 18 multiple regression models. In addition to AT and skeletal muscle, the following associations were found: skin, liver, and bone were main contributors to obesity-tissue composition; liver, kidneys, and heart to resting energy expenditure; and skin, liver, and bone to metabolizable energy and protein contents. A pronounced sexual dimorphism was present in all three models.

Conclusions: Obesity is characterized not only by excess AT but by increases in the masses of other "companion" organs and tissues and their related metabolic properties.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adipose Tissue / physiopathology*
  • Adult
  • Aged
  • Aged, 80 and over
  • Body Composition / physiology*
  • Energy Metabolism / physiology*
  • Female
  • Healthy Volunteers
  • Humans
  • Male
  • Middle Aged
  • Obesity / physiopathology*
  • Young Adult