By John Salak –
Yet another reason to shed excess pounds. Obesity is not only linked to heart disease, diabetes and other unwelcomed problems. Now scientists in Japan have linked it to hair loss.
In technical terms, researchers from the Tokyo Medical and Dental University (TMDU) discovered that significantly overweight individuals can suffer from a depletion of hair follicle stem cells (HFSCs) because their weight induces certain inflammatory signals that block hair follicle regeneration, which in turn leads to a loss of hair follicles.
Early in life HFSCs self-renew every hair follicle cycle, which is part of the process that allows hair to repeatedly grow back. As people age, these stem cells lose their ability to replenish themselves, which results in hair thinning or balding. The Japanese researchers found that poor diets and ultimately obesity accelerates hair follicle loss in mice, which is probably consistent in people. 
“High-fat diet feeding accelerates hair thinning by depleting HFSCs that replenish mature cells that grow hair, especially in old mice,” said Hironobu Morinaga, the study’s lead author.
The TMDU team went on to compare the difference in hair loss between overweight mice fed a high-fat diet (HFD) and those of normal weight among mice of the same age and discovered that heavier mice demonstrated faster hair loss.
“Even with HFD feeding in four consecutive days, HFSCs show increased oxidative stress and the signs of epidermal differentiation,” Morinaga said, underscoring the link between diet and hair loss.
If high-fat diets aren’t enough to worry about when it comes to hair loss, Harvard University confirmed a centuries-old belief on why people go bald. Lots of stress equates to less hair on top.
These Boston-based researchers discovered that chronic stress knocks the stuff out of HFSCs by putting them in an extended resting phase, which thwarts hair growth. The group even identified the specific cell type and molecule responsible for sending the stress signal to the stem cells causing them to shut off.
The good news about this discovery is that this pathway now potentially can be targeted to rebuild hair.
Mice, again, were critical to this hair-related find. The Harvard researchers went about their work by introducing corticosterone, a major stress hormone produced by the adrenal glands, to mice. This hormone is equivalent in humans to cortisol, which is often referred to as the “stress hormone.”
The mice with elevated levels of corticosterone causing chronic levels of stress had their HFSCs remain in a resting phase for extended periods, which undermined their ability to regrow hair.
“This result suggests that elevated stress hormones indeed have a negative effect on hair follicle stem cells,” said Ya-Chieh Hsu, an associate professor at Harvard and the senior author of the study.
“But the real surprise came when we took out the source of the stress hormones.”
By removing the stress hormones, Hsu reported that the resting phase of the cells became extremely short and that these mice continued to regenerate hair follicles throughout their lives.
“So even the baseline level of stress hormone that’s normally circulating in the body is an important regulator of the resting phase. Stress essentially just elevates this preexisting ‘adrenal gland-hair follicle axis,’ making it even more difficult for hair follicle stem cells to enter the growth phase to regenerate new hair follicles,” Hsu said.
It is debatable, of course, whether Harvard and TMDU have nailed down an absolute solution for the glabrous. But their findings might encourage many to eat and worry less.
