Fettmassa

Fettmassa, or fat mass, is the total mass of adipose tissue in an organism, typically expressed in kilograms or as a percentage of total body mass. It is a major component of body composition, alongside fat-free mass, which includes muscle, bone, and organ tissues. Adipose tissue stores energy as triglycerides, cushions organs, and provides insulation. It also functions as an endocrine organ, secreting adipokines such as leptin and adiponectin that influence appetite, metabolism, and inflammation.

Two main categories of fat mass exist: essential fat, which is necessary for normal physiological function, and storage fat, which accumulates in adipose tissue. In humans, adipose tissue mainly consists of white adipose tissue, with brown adipose tissue present in smaller amounts, particularly in infants and some adults, capable of thermogenesis.

Measurement and units: Fat mass can be quantified by body composition assessment methods, including dual-energy X-ray absorptiometry (DEXA), hydrostatic weighing, air displacement plethysmography, skinfold measurements, and bioelectrical impedance analysis. Results are reported as absolute fat mass (kg) or as body fat percentage; some uses apply a Fat Mass Index (FMI in kg/m^2).

Health relevance: The amount and distribution of fat mass influence health. Excess fat mass, especially visceral fat around internal organs, is associated with obesity-related risks such as metabolic syndrome, type 2 diabetes, and cardiovascular disease. Very low fat mass can also be problematic, affecting hormonal balance and energy reserves. Sex and age affect fat distribution: men tend to accumulate more visceral fat, while women store fat subcutaneously; distribution patterns can shift with aging and hormonal changes.

In practice, fettmassa is used to assess body composition in medicine, nutrition, and sports to monitor weight management and fitness.