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New Studies show: Fat Causes Inflammation

by Caroline J. Cederquist, M.D.

For many years, the conventional wisdom about fat was that it was essentially just the body's fuel storage facility: inert, convenient and pretty cute on babies.

But too much of it on grownups, and we tend not to think it's so cute. And now recent research has shown that it's not so inert, either. Your body's fat isn't just passively storing energy until you need it. It turns out there are other things going on in there, sinister things that could be causing you health problems.

Everybody knows that excessive weight aggravates, even causes, many unhealthy medical conditions, including bone and joint disorders, cardiovascular disease, pulmonary problems and diabetes.

Fat's role in some of these problems has often been attributed to what might be called the physical effects of the excess weight: the wearing burden of weight on bones and joints, the buildup of plaque that reduces blood flow through major arteries, the crowding of fat around critical body organs, causing strain on those systems.

But it's the role fat plays at the chemical level that is of growing interest today, because one of the most important revelations to come from these recent studies that fat is actually producing chemicals that cause inflammation, a key player in all those troublesome and dangerous diseases.

Integrated systems

Weight problems are typically regarded as issues of the metabolic system, while inflammation has been seen as a function of the immune system. In its normal role, inflammation is a protective device, defending the body against outside invaders. But it becomes an unhealthy condition when it reacts excessively, or in extreme cases, mistakenly attacks healthy tissues, as with rheumatoid arthritis.

The metabolic and immune systems actually are bound together. That's created certain problems through most of human history, because when people are malnourished or starving--which remains a problem in undeveloped portions of the world--their metabolism slows down, trying to conserve every bit of energy it can. And this in turn suppresses the immune system which is then less able to fight off disease.

But here in the United States, we're facing a problem at the other end of the scale. With roughly two thirds of the population now overweight, a different set of complications and problems has emerged from the immune/metabolic relationship, the most prominent of which is excess inflammation.

That's because fatty tissue is made up of adipose cells, which increase in size but not number as more fuel is presented to the body for storage. These cells produce something called cytokines, small, secreted proteins that among other things, produce and regulate immunities and inflammation. And as adipose cells grow larger, they produce more cytokines, leading to more inflammation.

Not only that, but in amongst the fatty adipose cells are other cells called macrophages, which also produce cytokines. There are normally a few macrophages in the fatty tissue of even slim people, but as people become heavier, gradually at first and then at an increasing rate, the proportion of macrophages in fatty tissue increases.

Now, you wouldn't want to be without macrophages-- these are the immune system's first line of defense, patrolling the body for infection and cleaning up after cells as they naturally die off. So you want-- actually, need--a normal number of these little guys distributed throughout your tissues.

But it turns out that in overweight people, most of the inflammation promoting cytokines in fat are coming not from the adipose cells themselves, but from these macrophages!

The clean-up crew

So what is it that attracts the extra macrophages, with their dangerous cargo of inflammatory cytokines, into the fatty tissue to begin with'

Recall that as people become increasingly overweight, they do not grow more adipose cells; the ones they have simply swell to larger and larger size. Inevitably, some of them become so overburdened that they burst open, leak, or just die. It is the resultant mess of cellular waste that the macrophages come rushing in to clean up, after all, that's their job!

But with that clean-up mission, you get all that excess inflammation that they bring, and you know what that means: more heart disease, more arthritis, more diabetes, more asthma.

But wait! You may say, that's great! That means we can just surgically remove some of our fat--and all its macrophages with it--- and thereby reduce our risk of those diseases!

As usual, there's no easy way out of the health problems caused by excess weight. Liposuction can't bail us out of inflammatory heart disease or arthritis. That's because not all fat is created equal.

Visceral fat that's packed in around the organs in our abdominal cavity---where no cosmetic surgeon can vacuum it away--that's the stuff that's packing all the inflammatory activity, whereas the subcutaneous body fat hanging around our hips and arms, not so much.

When people underwent fat-reduction surgery for cosmetic purposes, a process that removes primarily that subcutaneous body fat, they had no improvement in their inflammation measures at all.

But in another study, when only visceral fat was removed from a group of extremely obese men who had insulin resistance, by one year after surgery, 95.6% of the men no longer had insulin resistance. They still had all their excess body fat, but the most of the inflammatory cytokines associated with insulin resistance had been taken out of commission.

Obviously, that's extremely dangerous surgery, and very heavy people are exceptionally high-risk candidates for major surgery anyway, so there's no quick fix there.

But the same old good news as always remains: weight loss through diet and exercise will improve the situation. Several studies have confirmed that as overweight people lose weight through those simple-- -though not necessarily easy--lifestyle changes, those inflammation-producing cytokines are reduced and numerous health measures improve.

Finding the inflammatory properties of fat is one of those discoveries that doesn't readily offer any easy solutions, but it sure helps explain why excess weight causes so very many problems.

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