Facts about fat

Did you know that there are different types of fat and that obesity is defined as a disease in itself? Find out more about fat.

Text: Fredrik Hedlund, first published in the magazine Medical Science 2015.

Different types of fat

Brown fat

Babies are born with a significant amount of brown fat to help keep them warm. The proportion of brown fat shrinks as we get older, but recent research has shown that human adults also have a significant amount of brown fat that helps maintain body temperature during cold conditions.

White fat

The vast majority of fat in adult bodies is white fat. This type of fat stores energy, but cannot burn it.

In between

A new type of fat cell has recently been discovered which looks like white fat, but works like brown fat and has been given the name brite, from “brown into white” White fat cells are transformed into brite cells when it is cold. But researchers have now found a way to chemically stimulate white fat cells to become brite cells. Even if this is a long way from becoming a reality, this is a possible pathway for a future drug that will be able to burn fat.

Diseases caused by obesity

Obesity is defined as a disease in itself. In addition it carries with it an increased risk of the development of other diseases.

  • Type 2 diabetes
  • Cardiovascular disease
  • Sleep apnoea
  • Liver disturbances
  • Musculoskeletal problems
  • Infertility
  • Cancer
  • Psychological problems (women in particular have an increased risk of depression, bipolar disorder, panic disorder and agoraphobia)

Who is obese?

BMI thresholds, kg/m2

Body Mass Index, BMI is calculated by dividing weight by height, squared (kg/m2).

  • Underweight: < 18,5
  • Normal weight: 18,5–24,9
  • Overweight: 25–29,9
  • Obesity x 3: Obesity Grade I, Obesity Grade II, Obesity Grade III

Waist circumference

Provides a good indication of the risk of developing consequential metabolic diseases.


  • Increased risk: 94-102 cm
  • Very increased risk: > 102 cm


  • Increased risk: 80-88 cm
  • Very increased risk: > 88 cm

Criteria for surgery

Criteria that are currently used in Sweden: BMI >= 40 or BMI >= 35 with obesity-related morbidity. (some county councils in Sweden use BMI over 35 regardless of comorbidity).

Liposuction a cosmetic intervention

As opposed to the surgical methods, liposuction does not have any positive impact on other morbidity. Metabolic morbidity remains the same five years after liposuction, despite a large weight reduction.

Exercise does not reduce weight

Physical activity is very important for general well-being and for creating muscles that burn more fat. Exercising also has a clear effect on the dangerous abdominal fat. But as a method of weight loss its results are discouraging. Objective measurements show that obese adults and children are just as mobile as those of a normal weight. And exercise as a weight-reduction treatment shows a redistribution from fat to muscle, but no effect on weight.