'Healthy Obese' Is Possible, But Maybe Not Forever

Illustration for article titled Healthy Obese Is Possible, But Maybe Not Forever

As many as a third of obese adults are considered metabolically healthy, meaning they have normal cholesterol and blood pressure levels and show no signs of developing diabetes. Still, they're considered a medical mystery, but new research has shed some light on why some people can be healthy at any size, while others cannot.

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It has to do with fat cells, according to a new study in the journal of Diabetologia. Compared to obese people who are healthy, those who are metabolically unhealthy have "impaired mitochondria" and a "reduced ability to generate new fat cells."

What researchers found was that in a healthy obese person, new cells are generated to help store fat as it accumulates, whereas the cells of an unhealthy obese person "swell to their breaking point," making their fat cells larger than any other group.

They were swollen and riddled with inflammation. The breakdown and mobilization of their fat stores was suppressed, and a closer look showed that their mitochondria were malfunctioning. Their ability to burn fuel and produce adenosine triphosphate, or ATP, the body’s energy currency, was reduced.

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It leads to ectopic fat accumulation, meaning that fat gets into organs like the heart and liver. (A fatty liver is linked to Type 2 diabetes.)

However, for a healthy obese person, the fat doesn't travel throughout the body, and remains just beneath the skin, where it doesn't seem to cause any physical harm.

A study that appeared in the journal Diabetes Care in August found that metabolically healthy obesity is more frequently found in younger adults, but it may be a transition state, and that "some, if not many, people in this category will eventually develop the expected metabolic disturbances."

Dr. Jussi Naukkarinen, the lead researcher in the fat cell study, said that anti-inflammatory drugs have been shown to "protect mitochondrial function and improve diabetic symptoms and glucose metabolism." He also suggests that high glycemic foods (like sugar and white flour) play a role in spiking blood glucose and insulin levels.

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But ultimately, he believes that studying healthy obese people will help those that are unhealthy.

"People haven’t really paid that much attention to metabolically healthy obesity, but I think it can teach us a lot about usual obesity,” he said. “It’s only recently that people studying depression have done happiness studies showing what goes right, and I’m thinking about the metabolically healthy obese phenomenon in the same way.”

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Image via xrender/Shutterstock

The ‘Healthy Obese’ and Their Healthy Fat Cells [NYT]

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DISCUSSION

cassiebearrawr
ʕ•ᴥ•ʔ : Bear Privilege is a Liberal Hoax

There's actually a lot more going on here than the article says. The main metabolic problem in obesity is that adipocytes (fat cells) actually swell to the point where they exceed the diffusion radius of the surrounding capillaries, and so they become hypoxic (not enough oxygen). Mitochondria need oxygen to generate ATP (in a process called oxidative phosphorylation) and when they don't get enough, this activates a whole stress response cascade in cells that basically results in a state of chronic, low-grade inflammation for the entire body. The cells release growth factors such as VEGF (vascular endothelial growth factor) that SHOULD increase angiogenesis and vasculogenesis (new blood vessel formation), but for whatever reason they don't. And what you wind up with is rarefaction: a dying off of capillaries that serve as the site for exchange for nutrients. And so the cycle feeds back on itself, with adipose tissue serving as a massive reservoir for cytokines (intercellular signaling molecules) that cause problems in other parts of the body. Particularly diabeetus. But in metabolically healthy obese people, this problem doesn't manifest, or at least not to the same degree. Their adipose tissue doesn't become hypoxic and so this whole metabolic feedback loop doesn't really happen. And that's actually more a function of forming new blood vessels than new adipocytes.

I know way, way too much about this topic because I had to do a report on it recently. Needless to say, it's a really interesting phenomenon.