Obesity Chapter 8


Choking Your Organs

PART 1

Fat Is an Active Organ

For many years, adipose (fat) tissue was thought to be a mostly dormant substance with a mainly passive function: storage. But now researchers have found that adipose tissue is, in fact, highly active. Adipose tissue has a metabolic function and acts as an endocrine organ—that is, it produces hormones and secretes them into your bloodstream, through which they travel to affect the function of organs all over your body. In fact, fat tissue produces literally dozens of hormones, including leptin, which controls appetite, and adiponectin, which affects insulin sensitivity and blood sugar levels. Because adipose tissue is now known to be so biologically active, researchers think that it could well play an important role in cardiovascular disease, diabetes, cancer, and other diseases. READ MORE

Fat cells are also important contributors to your immune system and its inflammatory response. Adipose tissue produces many substances, including free fatty acids and cytokines, proteins that affect cell signaling and behavior. Cytokines have an important role in regulating immune system functions. Scientists have identified dozens of different cytokines produced by fat cells, called adipokines. They include interleukins, tumor necrosis factor, and interferons, which trigger inflammation and respond to infections.

Visceral Fat vs Subcutaneous Fat
Visceral fat is an especially dangerous type of fat to have in excessive amounts. This type of fat is found deep inside your abdomen, where it surrounds your vital organs. It’s not the kind of fat you can pinch on your belly—that’s subcutaneous fat, found directly under your skin. But if you carry a lot of subcutaneous fat on your belly, it’s a pretty good bet you have an overabundance of visceral fat, too.

There is no doubt that visceral fat is linked with greater risk for diabetes, cardiovascular disease, hypertension, and certain cancers. Why and how that happens, though, is still not clear.

Right into the Liver
All the fat in your body is supplied with blood through your circulatory system. In other areas of your body where fat is deposited, the blood flows through the fat tissue and then drains into your systemic circulation. But visceral fat is different. The blood that circulates through it drains into the portal vein, which leads directly into your liver. The portal vein is the major source of blood supply to the liver and is responsible for 80% of total liver blood flow.

That means that all the dangerous substances your visceral fat produces all pour directly into your liver. Scientists think this may have important, and damaging, consequences.

The Suspects:

Lipoxygenase
People with diabetes have increased levels of an inflammatory enzyme called lipoxygenase in their visceral fat. Inflammation is thought to be a key factor in developing diabetes.

Free Fatty Acids
Among the other suspects are free fatty acids (FFAs). Visceral fat normally produces FFAs, and when you’re obese, excessive amounts of these fatty acids are delivered into your liver. They may lead to fatty liver disease and affect your liver’s production of blood lipids, including cholesterol. Excess visceral fat is directly linked with higher LDL-cholesterol, lower HDL-cholesterol, higher total cholesterol, and insulin resistance.

Adipokines
The fat cells of obese people are giant, much larger than normal fat cells. They are also more active than normal fat cells and secrete a greater amount of metabolically active chemicals, including inflammatory adipokines. Inflammatory adipokines secreted by your visceral tissue include interleukin-1 (IL-1), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and resistin. Many investigators have suggested that one or more of the adipokines secreted by visceral fat cells create chronic systemic inflammation and lead to insulin resistance, type 2 diabetes, and other disorders, including high blood pressure.

Adipokines, such as IL-1, IL-6, tumor necrosis factor-alpha, and resistin, are all delivered into the liver via the portal vein. It’s theorized that these inflammatory substances damage the functioning of the liver and set the stage for many metabolic disorders, such as insulin resistance. It’s known, for example, that the adipokine resistin is linked to insulin resistance—which is the reason it was named “resistin.”

How Does That Work, Exactly?
But it’s hard to understand exactly the mode of action of these chemicals. For one thing, it’s very difficult to gain access to blood from your portal vein. One group of researchers, however, was able to obtain samples of portal vein blood from 25 obese patients during bariatric surgery. Their focus was the inflammatory adipokine IL-6. They discovered that concentrations of IL-6 were much higher in portal vein blood than in peripheral artery blood. This confirmed that visceral fat is an important source of IL-6 production in obese people.

In the liver, IL-6 is known to stimulate the production of inflammatory components, slow the conversion of glucose to glycogen for storage in the liver (a function mediated by insulin), and increase gluconeogenesis (the formation of glucose from noncarbohydrate sources). Increased concentrations of IL-6 in the blood are associated with heightened risk of developing type 2 diabetes and cardiovascular disease. The researchers also found that portal vein IL-6 concentrations correlated directly with blood levels of systemic C-reactive protein (CRP). CRP is a marker of inflammation: its levels rise in response to increasing inflammation.

All these observations show a possible mechanism for the relationship between visceral fat, insulin resistance, and systemic inflammation. IL-6 is very likely implicated, but it may be that numerous other inflammatory adipokines secreted by visceral fat are involved as well. LESS
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PART 2

Let Me Catch My Breath

Being obese can make it difficult for you to breathe fully and naturally. As fat accumulates inside of your abdomen, it starts to crowd your internal organs and muscles, particularly the diaphragm. It can restrict blood supply to your vital organs, and it also makes it hard for your diaphragm to do its work. READ MORE

Your diaphragm is dome-shaped a sheet of muscle that separates your chest from your abdominal cavity. When you inhale, your diaphragm contracts (tightens) and moves downward, creating a vacuum in your lungs and causing air to rush into them. The downward contraction of your diaphragm increases the space in your chest cavity, allowing your lungs to expand. The intercostal muscles between your ribs also help to enlarge the space in your chest. These muscles contract as you inhale, pulling your rib cage both upward and outward.

Heavy Breathing
When you’re obese, and especially if you’re carrying a lot of visceral fat, the downward movement of your diaphragm is limited by the fat tissue filling your abdomen. Your diaphragm can’t move fully down into your abdomen, and so your lungs can’t fill deeply with air.

Another factor that can make it difficult for you to breathe deeply is the weight of fat on the chest wall. Your chest wall may become so heavy that the intercostal muscles between your ribs are unable to pull the rib cage upward and outward.

Is It Asthma?
Although there is a connection between obesity and asthma, some doctors think that up to a third of asthma diagnoses in obese people are misdiagnoses. Asthma is a chronic state of inflammation in the airways that sometimes flares up in an asthma attack. Symptoms of asthma include shortness of breath and rapid, shallow breathing—but these symptoms can also be caused by the difficulty of breathing deeply due to obesity. LESS
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PART 3

Obesity and Arthritis

Obesity is strongly linked with arthritis: about twice as many obese adults report having arthritis as nonobese adults, and two thirds of adults with diagnosed arthritis are overweight or obese. READ MORE

Arthritis is acute or chronic inflammation of the joints. A major factor in the association of obesity with arthritis is simply mechanical: the joints are overloaded due to excessive weight, and the result is joint degeneration and inflammation. Your knees and hips are especially vulnerable to the injurious effects of overweight because they bear the weight of most of your body. The force exerted on these joints is greater when you walk. A force of three to six times your body weight is exerted across your knee when you are walking, meaning that if you weigh 200 pounds, a force of 600-1,200 pounds is being exerted on your knee with each step. An increase in body weight increases the force by this amount: being only 10 pounds overweight increases the force on the knee by 30-60 pounds with every step.

More Than Just Mechanics?
However, there may be more to obesity-related arthritis than simple overloading. Being obese increases the likelihood of having osteoarthritis in your hands, although the joints of the hands are not load-bearing. A study conducted with mice showed that mice who became extremely obese had no arthritis if their bodies didn’t have leptin. Leptin, a hormone produced by fat cells, is associated with appetite regulation and is found at high levels in obese people. LESS
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The material on this site is for informational purposes only and is not intended as medical advice. It should not be used to diagnose or treat any medical condition. Consult a licensed medical professional for the diagnosis and treatment of all medical conditions and before starting a new diet or exercise program. If you have a medical emergency, call 911 immediately.