Can we burn more FAT in cold weather? (Soberg et al., 2021)

There are two types of Body Fat
1. White adipose tissue (WAT); more common
2. Brown adipose tissue (BAT)

BAT produce heat when exposed to cold. Put simply, BAT burns extra energy so we can stay warm. Repeated exposure to the cold is associated with increased BAT activity.

Soberg et al., (2021) assessed whether BAT activity differed between 8 winter swimmers and 8 controls exposed to both cold and warm temperatures. The secondary outcomes were energy expenditure, gene expression in WAT, and skin and core body temperature

Findings
Both groups had similar BAT activity in cold period.
Only controlled group showed clear BAT activity in warm period.
-No difference in REE between two groups during warm period.
-Winter swimmers had higher Resting Energy Expenditure in cold period.
-Winter swimmers burned extra 20 Calories in cold period and control group only burned extra 9 Calories (18 Calories per hour) compared to warm period.

Practical application
According to this study, you only burn extra 18 Calories per hour with exposure to cold weather. You can burn way more Calories than that simply by engaging in moderate activities.
In previous studies brown fat on energy expenditure in cold temperature ranged from 25-400 Calories per day.
Obese individuals have lower BAT activity. In other words, people who need it the most have the least effect.
At this stage we don’t know how to activate BAT, there’s no real point focusing on that.

Fun Facts about BAT
BAT is detectable in Infants & Children and total BAT decline throughout life.
An average person has around 0-600g of BAT.
BAT is present in the neck, along the spine, and in the supraclavicular area (where it is most active).

Reference:
Søberg S, Löfgren J, Philipsen FE, Jensen M, Hansen AE, Ahrens E, Nystrup KB, Nielsen RD, Sølling C, Wedell-Neergaard AS, Berntsen M, Loft A, Kjær A, Gerhart-Hines Z, Johannesen HH, Pedersen BK, Karstoft K, Scheele C. Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men. Cell Rep Med. 2021 Oct 11