The annual tradition of breaking a New Year’s resolution is observed perhaps just as strictly, if regretfully, as that of making one. Research into motivation, for instance, knows that for a task to be accomplished, the actor must genuinely want to complete it — wanting it to be completed isn’t enough. But for people looking to lose weight in 2014, science offers some mercy, as a new study suggests age-related fat storage may make losing weight more of a biological issue than purely a motivational one.
Researchers from the University of Shizuoka have discovered that the “good” brown fat located behind our necks and shoulders, which burns the “bad” white fat that accumulates on our stomachs and thighs, diminishes as we age. The exercise needed to burn a sufficient number of calories begins to increase because a slower, less industrious metabolism replaces the heavy lifting once performed by the brown fat. Fortunately, the team’s new research suggests the existence of a metabolic on/off switch that may help delay this process.
The discovery came after researchers observed two groups of mice. One group remained normal to serve as the control, while the other had a specific gene — known as the platelet-activating factor receptors (PAFR), which encode a protein responsible for inflammation and lipid transfer — knocked out. Mice in the knockout group grew far more obese over the study period, characterized by increases in body mass (25 percent) and epididymal fat mass (55 percent). After controlling for other possible influences, researchers determined the increased obesity was a result of impaired function in the brown adipose tissue (BAT) — in other words, brown fat.
The upshot to this is a newly forged path for research. If future experiments can better target the specific molecular pathway that deactivates the PAFR gene, scientists may be able to develop pharmacological approaches to treat many of today’s common ailments, such as diabetes, high blood pressure, heart disease, cancer, infertility, and ulcers.
Until a few years ago, brown fat was believed to carry no benefit for adult humans. Scientists believed the substance was only beneficial to mammals that didn’t shiver, such as rodents and babies, so they could keep warm. Both groups have larger quantities of brown fat on their shoulders and backs, near their spines, compared to adult humans. And since adult humans shiver to keep warm, nobody believed humans had any.
But then three studies emerged that showed adults do have brown fat and that is serves a purpose outside of thermogenesis. When the body engages in physical exercise, brown fat stores consult the ordinary fat stores and burn them for fuel. One recent study found that men who were exposed to a chilled environment, but not so cold as to make them shiver, saw an 80 percent spike in their metabolic rates. What’s more, the men who started shivering later had greater stores of brown fat.
A separate study showed mice who exercised relied on a different source of brown fat —quantities interspersed in white fat, not in self-contained chunks — to burn energy. The takeaway from that study, notes Dr. Bruce Spiegelman, co-researcher and professor of cell biology and medicine at the Dana-Farber Cancer Institute, is that human metabolisms work in a similar fashion. But as the present researchers acknowledge, these functions degrade as we age, causing us to resolve ourselves, year after year, to an even steeper uphill battle.
“A common complaint is that older people have to work twice as hard with their diets and exercise to get half of the results of younger people," Dr. Gerald Weissmann, editor-in-chief of The FASEB Journal, said in a statement. "Now we have a much better idea why this is the case: Our brown fat stops working as we age. Unfortunately, until a way to turn it back on is developed, we'll have to be prepared to eat more salads and lean proteins, while logging more miles on the treadmill than our younger counterparts."
Source: Sugatani J, Sadamitsu S, Yamaguchi M. Antiobese function of platelet-activating factor: increased adiposity in platelet-activating factor receptor-deficient mice with age. The FASEB Journal. 2013.