Caloric restriction is known to increase lifespan. It also turns your fat beige.
Caloric restriction is a terminus technicus scientists use for a practice almost everybody has undergone, one way or the other. Fasting. Dieting. Eating less for an extended period of time. Caloric restriction is overall healthy and very distinct from malnutrition or starvation, where essential nutrients and vitamins are not consumed.
Surprisingly, real interest in caloric restriction developed after scientists discovered that almost all species gain profound longevity compared to their fully-fed peers. No matter if yeast, fruitfly, worm or even primate, caloric restriction prolonged lives. In primates by several years, and in the roundworm even up to 50% of the natural lifespan.
These observation prompted an increased research interest to figuring out the biology of aging, with many respectable researchers currently working on its many aspects.
One established, but incomplete theory of aging promoted by gerontologists (= aging researchers) encompasses the following causes:
- DNA damage theory of aging/epigenetic clock
- loss of cellular function by imbalance, wear out or external insult
- Accumulation of damages on molecular/cellular/extracellular level
No matter how you look at it, a body is a biological machine and the longer it runs, the more chances it has to get broken beyond repair. In order to live longer, we need to reduce sources of potential damage.
How caloric restriction would fit into this picture is quite unclear, since eating usually does not cause damage to our cells or DNA, at least not directly.
Now, researchers from the University of Geneva, Switzerland, reported that caloric restriction leads to production of so-called “beige” adipose tissue, a fatty tissue usually associated with a “lean and healthy” phenotype, by utilizing signaling pathways from our immune system.
Originally, it was believed that humans have only “white” and “brown” fat depots, and that these tissues work quite differently from each other. White adipose tissue is a storage facility, where we store energy in the form of lipids to consume them at a later starvation period. “Brown” fat tissue does not store energy, but rather burns lipids to produce heat. However, around a decade ago researchers discovered an “intermediate” form, termed “beige” fat; where brown fat cells emerge within white adipose tissue, in this case once scientists exposed animals to cold.
Which makes sense, since we know that only brown fat cells can produce heat from stored lipids, a process called non-shivering thermogenesis.
In their research, Fabbiano S. et al. discovered that this “browning” of fat is mediated by type 2 immune response signaling. Canonically, type 2 immune response was thought to be host-protective and helpful to limit the harm done by the primary type 1 immune response, but recently our immune system has been involved in many cellular processes, including metabolism.
We hypothesized that energy scarcity could be a physiological trigger that drives the browning of the white fat. In this study, we found that CR (=caloric restriction) promotes functional beige fat development. We show that the browning is concomitant with the increased type 2 cytokine signaling and that this signaling is necessary for the beige fat development, for the decrease of the subcutaneous fat, and for many of the metabolic improvements caused by the CR. — Fabbiano et. al.
This “browning” of white adipose tissue is a favorable ability, since it allows our body to improve on critical aspects of our metabolism like insulin sensitivity, a primary function dysregulated in metabolic disease and diabetes. In general, metabolic dysregulation has now been associated with many diseases, from arteriosclerosis to cancer, notwithstanding all damages done to ourselves by being overweight. We assessed before that one way to live longer is to avoid damaging the biological machine, which is our body. A dysfunctional metabolism as a surefire way to the grave, yet we lack understanding and tools to tinker with our metabolism efficently.
The insights into beige fat generation via immune signaling might offer potential new avenues to tweak our metabolism, while at the same time reducing our fat deposits.
And who in the world would not want to live longer with the side effect of losing some weight?
This story is part of advances in biological sciences, a science communication plattform that aims to explain ground-breaking science in the field of biology, medicine, biotechnology, neuroscience and genetics to literally everyone. Scientific understanding has too many barriers, let’s break them down!
