How Body Fat Benefits Health in Unexpectedly Complex Ways

Body fat is often misunderstood as merely a passive energy reserve. However, emerging research indicates it plays a crucial role in our overall health, providing insights into its intricate functions.

Fat comes in various forms, including white fat, which stores energy and releases hormones influencing metabolism; brown fat, known for generating heat; and beige fat, which activates thermogenesis under specific conditions. The location of these fats matters significantly. While subcutaneous fat is usually harmless, visceral fat, located deep in the abdomen, is closely linked to inflammation, type 2 diabetes, and cardiovascular diseases.

Recent studies further clarify this dynamic, suggesting that adipose tissue is actively involved in regulating blood pressure and managing immune responses in crucial areas of the body.

A study led by Jutta Jarkanen at Karolinska University Hospital in Stockholm examined the cellular structure of visceral fat in various abdominal locations. Their findings highlighted that epiploic fat, which envelops the large intestine, is abundant in immune cells and specialized fat cells producing inflammatory proteins tied to immune activation. They discovered that microbial products from the intestines trigger these fat cells to activate nearby immune responses.

“Our research indicates that fat deposits are specialized based on their anatomical position, particularly the fat adjacent to the intestine, which is tailored for immune interactions,” Jarkanen noted.

Although the study included obese participants, everyone has some visceral fat around their intestines, suggesting that epiploic fat fulfills a fundamental role irrespective of body weight.

“The gut continually encounters nutrients, microbial elements, and environmental substances,” Jarkanen explained. “Having adjacent adipose tissue to sense, respond, and manage immune reactions adds an extra layer of defense.”

However, obesity can lead to chronic overactivity in this system. Overeating, excessive consumption of particular foods, and specific bacterial compositions in the gut microbiome can lead to persistent immune signaling in intestinal fats, contributing to low-grade inflammation linked with metabolic disorders like type 2 diabetes and obesity.

A follow-up study unveiled yet another surprising function of fat: its role in regulating blood pressure. Marcia Koenen and colleagues at Rockefeller University aimed to understand the connection between obesity, characterized by excessive white fat, and high blood pressure, while noting that brown and beige fats seem to offer protection.

The team investigated perivascular adipose tissue, a beige fat-rich layer encasing blood vessels. In genetically modified mice that lack beige fat, their blood vessels exhibited stiffness and overreacted to daily hormonal signals that constrict arteries, resulting in elevated blood pressure.

The researchers identified that the enzyme QSOX1, secreted by dysfunctional fat cells, caused this adverse effect. Blocking this enzyme prevented vascular damage and normalized blood pressure in the mice, independent of their body weight. “This emphasizes the importance of inter-organ communication in understanding complex diseases such as hypertension,” emphasized Koenen.

“This study sheds light on the often-underestimated roles of brown and beige fat,” noted Christy Townsend from Ohio State University. Though human perivascular adipose tissue is proportionately less substantial than in mice, it remains physiologically relevant. “This research highlights the need for a nuanced understanding of fat’s effect on health beyond overall fat mass and BMI.”

Instead of merely focusing on fat reduction, these findings point towards future therapies aimed at preserving or restoring the advantageous functions of fat by targeting specific fat deposits, enhancing immune-fat communication, and maintaining healthy beige fat activity. However, comprehensive research is necessary before these findings can be applied clinically.

Together, these studies position adipose tissue as an active, functionally diverse system implicated in numerous aspects of human physiology. “When I began working in this field in the late 1990s, the belief was that fat was just a sack of cells storing extra nutrients,” stated Paul Cohen, also from Rockefeller University, who participated in the second study. “These investigations reveal a shift in our understanding of fat as not just a single cell type, but a complex tissue composed of various cell types engaged in diverse processes, extending far beyond simple nutrient storage and mobilization.”