Two hours a day in 17°C air for six weeks took 0.7 kg of fat off young men
The 2013 Journal of Clinical Investigation study gave Japanese men two hours of cool air a day and compared their body fat with a control group's.
The paper
Recruited brown adipose tissue as an antiobesity agent in humans
Yoneshiro T, Aita S, Matsushita M, Kayahara T, et al.. Journal of Clinical Investigation, 2013;123(8):3404-3408.
See the study at a glance
- Design
- Screening study plus a randomized six-week trial
- People
- 51 men screened; 22 in the six-week trial
- Who they were
- Healthy young men in Japan. The six-week trial took 22 men with low or undetectable brown fat: 12 in the cold group and 10 controls.
- What they did
- Two hours a day in 17°C air for six weeks, while controls went about their usual lives. The screening tests used two hours at 19°C.
- How long
- 6 weeks
These numbers came out of it
−0.70 kg
The cold group lost 0.70 kg of body fat over six weeks. Controls gained 0.03 kg.
180.6
The extra energy the cold group burned when chilled rose by 180.6 kcal a day, against 5.0 in the controls. The authors scaled both figures up from two-hour tests.
~24 kcal
Once the daily figure is scaled back down, one two-hour session burned about 24 extra kcal after six weeks.
27 of 51
Brown fat switched on in the cold in 27 of the 51 screened men.
The researchers did this
Researchers in Japan first screened 51 healthy young men with scans during two hours at 19°C. Twenty-seven of them had brown fat that switched on in the cold.Source 1 · Randomized trialRecruited brown adipose tissue as an antiobesity agent in humansYoneshiro T, Aita S, Matsushita M, et al.. Journal of Clinical Investigation, 2013.Read the paper ↗PubMed ↗
For the six-week trial they took 22 men with low or undetectable brown fat. Twelve spent two hours a day at 17°C and ten went about their usual lives.Source 1 · Randomized trialRecruited brown adipose tissue as an antiobesity agent in humansYoneshiro T, Aita S, Matsushita M, et al.. Journal of Clinical Investigation, 2013.Read the paper ↗PubMed ↗ The cold group lost 0.70 kg of fat while the controls gained 0.03 kg. Men whose brown fat activity rose most tended to lose the most fat.
In the cold group, the extra energy burned when chilled rose from 108.4 to 289.0 kcal a day. Those figures take the difference between resting at 27°C and two hours at 19°C and stretch it to a 24-hour scale.Source 1 · Randomized trialRecruited brown adipose tissue as an antiobesity agent in humansYoneshiro T, Aita S, Matsushita M, et al.. Journal of Clinical Investigation, 2013.Read the paper ↗PubMed ↗ Scaled back to one two-hour session, the extra burn comes to about 9 kcal at the start and about 24 kcal after six weeks.
The study can't tell you these things
- The groups were small, and everyone was a young man.
- The men sat in cold air for about 84 hours over six weeks, so the result can't stand in for short plunges in water.
- Brown fat scans at the start and end cover 8 of the 12 men in the cold group.
- The trial lasted six weeks, so it can't say whether the fat stayed off.
People quote it like this
Claims that cold plunges burn fat through brown fat cite studies like this one. The men here lost 0.7 kg of fat over six weeks of daily two-hour sessions in 17°C air, and the cold never came from water.
We cited these sources
- 01Yoneshiro T, Aita S, Matsushita M, Kayahara T, Kameya T, Kawai Y, et al.. Recruited brown adipose tissue as an antiobesity agent in humans. Journal of Clinical Investigation. 2013;123(8):3404-3408. doi:10.1172/JCI67803 PMID 23867622