Do We Feel the Cold More as We Age? The Story of the Body’s “Heat-Producing Fat”

Many people say they feel the cold more as they get older. There can be many causes, such as loss of muscle mass, circulation and thyroid function. But one factor that researchers are paying attention to is the body’s “heat-producing fat”, brown fat.

Adults have brown fat, too

Brown fat is fat that uses energy to make heat instead of storing it. For a long time it was thought to exist only in babies and to be of little significance in adults. What changed this view was an analysis by researchers at Harvard Medical School in the U.S. (The New England Journal of Medicine).

The researchers re-examined 3,640 PET-CT scans (1,972 patients) taken to diagnose other conditions and found metabolically active brown fat from the front of the neck to the upper chest. The heat-producing protein UCP1 was also confirmed in tissue obtained through surgery.

Relationship with age and weight

• Brown fat was clearly visible in 7.5% of women and 3.1% of men, more than twice as high in women.
• With older age, brown fat was less likely to be found.
• It was seen more clearly in scans taken on colder days.
• Among older people, the higher the body mass index (BMI), the less brown fat there was.

Because these results come from an observational study, we cannot tell whether losing brown fat leads to weight gain or weight gain leads to losing brown fat. Even so, the finding that brown fat may be involved in adult metabolism became the starting point for many later studies.

White fat turning “beige”

Recent research focuses on the phenomenon in which some cells in white fat turn into “beige fat” that produces heat like brown fat when stimulated by something like cold, that is, browning. Cell and animal studies continue on which compounds are involved in this process, and a representative example is 4-HBA.

If you feel the cold unusually often and also have fatigue or weight changes, see a doctor to check for other causes such as thyroid function.