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The Omentum and Abdominal Fat: Health Benefits and Problems

Linda Crampton is an experienced teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.

The greater omentum hangs from the stomach like an apron. The liver has been lifted out of the way in this illustration.

The greater omentum hangs from the stomach like an apron. The liver has been lifted out of the way in this illustration.

Omentum Definition

The greater omentum is a fatty membrane that covers the small and large intestines. Until recently, its only function was thought to be the storage of fat. Now researchers have discovered that it not only has other functions but also has some important health benefits. It seems to be a "Jekyll and Hyde" structure, however. If it contains too much fat, it has the potential to cause serious health problems.

There are two types of fat in the abdominal area—subcutaneous and visceral. Subcutaneous fat is located under the skin and above the muscles. It's the soft fat that we can feel when we grab hold of our skin. Visceral fat lies below the muscles in the omentum and around the organs.

Excess visceral fat can have a more serious effect on our health than excess subcutaneous fat. Health experts say that those of us who have an apple-shaped body (one with excess fat in the abdomen) have a higher risk for certain health problems than those of us with a pear-shaped body (one which collects fat in the hips and thighs). An omentum containing a lot of fat contributes to the apple shape.

The stomach, small intestine, and large intestine; the longest part of the large intestine is the colon

The stomach, small intestine, and large intestine; the longest part of the large intestine is the colon

The Peritoneum

The peritoneum and the greater omentum are membranous structures in the abdomen. The peritoneum is a smooth, glistening membrane on top of connective tissue. It lines the abdominal cavity and covers the organs in the abdomen. It's a continuous sheet but is given different names according to its location. The parietal peritoneum lines the inside of the abdomen and the visceral peritoneum covers the organs. The omentum is made of the peritoneum.

The lesser omentum is attached to the lesser curvature of the stomach while the greater omentum is attached to the greater curvature.

The lesser omentum is attached to the lesser curvature of the stomach while the greater omentum is attached to the greater curvature.

The Greater and Lesser Omentum

An omentum is a sheet-like structure made of a double layer of peritoneum. It contains a variable amount of fat. There are actually two omenta—the greater one and the lesser one.

The greater omentum is attached to the greater curvature of the stomach, which is the outer curve furthest away from the midline of the body. (The curvature is shown in the illustrations above and below.) The greater omentum hangs over the small and large intestine, resembling an apron, and then folds back on itself to attach to the transverse colon. This is a horizontal section of the colon below the stomach. The greater omentum is often referred to as simply "the omentum".

The lesser omentum is much smaller than the greater one. It's attached to the lesser curvature of the stomach, which is the inner curve nearest to the midline of the body, and extends over the first part of the small intestine and the edge of the liver.

In most illustrations of the abdominal cavity, the omenta and peritoneum are removed in order to show the organs clearly. Some people may be surprised to learn that the structures and the membrane exist. This article focuses on the greater omentum.

Fat Storage

A healthy omentum is a thin, pale yellow sheet that contains fat and often has a lacy appearance. Fat is an essential substance in our body. It only becomes dangerous when it's present in an excessive amount or in the wrong place.

If the omentum absorbs extra fat, it becomes thicker and harder. An enlarged omentum may push the front of the abdomen outwards, producing a beer belly or potbelly.

For a long time, it was thought that the omentum wasn't important, except as a minor fat storage depot. Now there is evidence that it does more than just store fat and actually has some important functions.

The Immune System, Macrophages, and T Cells

The omentum contains "milky spots", which are collections of macrophages. Macrophages are a type of white blood cell and fight bacteria and viruses. The action of the macrophages in the omentum may help the immune system. This system protects us from disease.

Research suggests that the omentum may also suppress certain aspects of the immune system, at least in mouse cells studied in lab equipment. The discovery may or may not apply to the structure inside our body. The researchers examined the effect of mouse omentum cells on T cells (or T lymphocytes) in mice. T cells are a very important part of the immune system. They attack and destroy invaders such as bacteria, viruses, and cells from other people.

T cells become activated in order to do their job. The researchers mixed omentum cells with activated T cells in laboratory equipment and found that the T cells died. T cells that hadn't been activated were unaffected by the omentum cells. The cells apparently produced a substance that killed the activated T cells.

If this reaction occurs in humans it could be very significant. It may sound bad that T cells are killed, but in some conditions—such as organ transplants and autoimmune diseases—the immune system needs to be suppressed. An autoimmune disease is one in which a person's immune system attacks their own body. The discovery that the omentum may have the ability to dampen immune system activity could lead to improved methods for treating autoimmune diseases.

The Role of Stem Cells

An increasing number of researchers are finding evidence that the omentum functions in tissue repair and regeneration. In fact, some believe that this is the structure's primary job. Surgeons sometimes attach bits of omentum to damaged tissues in the body. They know from experience that this process stimulates tissue repair, but how it does this is uncertain.

The omentum may stimulate tissue regeneration because it contains mesenchymal stem cells, or MSCs. Stem cells are very important because they are capable of forming other cell types. This isn't true for the other cells in our body. In lab flasks, MSCs from the omentum have produced bone cells and cells that resemble lung cells.

Finding good sources of stem cells is important because they have the ability to repair damage. Human embryos are a good source of the cells, but the use of embryos is controversial. Obtaining the stem cells kills the embryos. Obtaining stem cells from adults (harmlessly) avoids this problem.

Visceral fat is stored around our organs and in our omentum. Although all excess fat can be dangerous, visceral fat may be especially so.

Dangers of Excess Visceral Fat

While the omentum seems to have some impressive and helpful functions, there's no doubt that excess visceral fat in the structure is dangerous. The fat cells are metabolically active and release a variety of chemicals. Some serve as messengers in the body and others trigger harmful inflammation. Fatty acids are also released from omental fat. These reach the hepatic portal vein, which transports them to the liver.

An excessive amount of visceral fat increases the risk of cardiovascular disease, hypertension (high blood pressure), high fasting blood sugar, insulin resistance, and type 2 diabetes. It also raises the blood level of LDL cholesterol (the so-called “bad” cholesterol) and increases the risk of certain types of cancer. In addition, it seems to increase the chance of someone developing non-alcoholic liver disease.

Men generally have a larger tendency to develop visceral fat in the abdomen than women. After menopause, a woman's tendency to store visceral fat increases, however. The tendency is also influenced by genetic factors.

Waist size may indicate the presence of visceral fat.

Waist size may indicate the presence of visceral fat.

Detecting the Presence of Hidden Fat

If we don't have a beer belly, how do we know that we have too much visceral fat? Health professionals say that our waist size is an indication that we're likely to have excess visceral fat and may be a more accurate indicator of potential health problems than the body mass index, or BMI.

For a person of average height, a waist size over thirty-five inches in females and over forty inches in males may be a warning sign. Another guideline states that a person's waist size should be no more than half their height.

People who have serious health, weight, or nutritional issues should visit their doctor to get lifestyle advice appropriate for their situation.

Lose Abdominal Fat: Follow a Healthy Diet

Reducing calorie intake and getting regular, moderately intense exercise is the best way to lose abdominal fat, according to many health experts. Severely restricting calories will probably make a diet very hard to maintain, however. The best plan is to make permanent and healthy lifestyle changes instead of "going on a diet".

Nutritionists generally recommend a diet that emphasizes unprocessed or minimally processed foods from plants and consists of vegetables, fruits, whole grains, legumes or pulses, lean protein, low-fat dairy, and moderate amounts of monounsaturated and polyunsaturated fats. Foods that contain healthy fats include nuts and seeds, some fish, and certain vegetable oils.

Some "healthy" foods may be high in calories, so it's important to be aware of the calorie content of foods. For example, fruit smoothies may be loaded with calories as well as nutrients.

Scientists have found that even a small amount of weight loss— five to ten percent of a person's weight—is likely to have substantial health benefits. It's a great goal to aim for even if it doesn't have a huge effect on a person's appearance. Some research indicates that visceral fat is lost before subcutaneous fat when we reduce our calorie intake.

Get Regular Exercise and Adequate Sleep


Anyone starting a new exercise program should begin with relatively easy exercise sessions that last for a short period. This will reduce the chance of injury. The intensity and duration of the sessions should increase slowly over time. Caution is also necessary when someone who already performs one type of exercise decides to start another type. If someone is very overweight, they should see a doctor before they start exercising.


Getting an adequate amount of sleep on a regular basis is also important in a healthy lifestyle. Interestingly, scientists have discovered that lack of sleep is linked to an increased amount of visceral and subcutaneous fat.

Whole grain bread is a good food for a healthy diet.

Whole grain bread is a good food for a healthy diet.

The Definition of Obesity

Some scientists have suggested that we need a new definition of obesity that is based on the location of body fat. A person who looks overweight may have a lot of subcutaneous fat but not much visceral fat. This person may be healthy and have a low risk of many serious health problems. (This is not necessarily the case, however. A doctor’s advice should be sought about any weight problem.) On the other hand, someone who looks thin may actually be unhealthy because they have a lot of visceral fat around their organs.

Sumo wrestlers are an example of people who look obese but are said to be relatively healthy. Most of their fat is subcutaneous, not visceral. However, when they retire from wrestling and regular exercise, the amount of visceral fat in their bodies increases.

Specialized medical scans can detect visceral fat, but most of us don't have access to these scans. The best that we can do is to follow a healthy lifestyle and monitor our waist size in relation to our height. Even if our waist size is appropriate, we don't know how much fat is hiding deep inside our abdomen below the omentum. A healthy lifestyle is therefore important for everyone.

References and Resources

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2013 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on September 06, 2017:

Hi, Vickie. I'm a science writer, not a medical practitioner, so I can't answer your question about whether your problem is linked to an omentum injury. I hope you're able to find a doctor who can give you a diagnosis and find a solution for your pain.

vickie zimmermann on September 06, 2017:

I am an obese lady of 58 who has been suffering for almost a decade with an area under the right breast. I am a nurse and when i lifted an obese patient, i felt a pop and burn high up in my right abdomen and saw a lump and marks that suggested bleeding under the skin. This thing comes out and feels like i am being pinched under my skin from the inside out. The only way I can get it to " go back in" is to avoid straining much, bending over or to splint myself. Visits to a herniologist suggest no hernia. They state the site has a very strong muscle group there. Hernia improbable. Now, i think it might be some sort of omental tear or herniation of the omentum that catches fatty tissue and causes pain. Is this possible? Tests for diagnosis? I am really lost but this pain has affected every aspect of my life. please help. My email is Any advice appreciated. thanks.

Linda Crampton (author) from British Columbia, Canada on May 17, 2017:

Hi, Thomas. I've never heard about what you've mentioned. I have read about fat cells being transformed into beta cells, but that's still an experimental procedure according to what I've read.

Thomas Sherwin on May 11, 2017:

Good info. I can now see why beta cell transplant into viseral fat is showing great results.......

Linda Crampton (author) from British Columbia, Canada on October 22, 2016:

Hi, terri. The omentum contains living cells that obtain oxygen and nutrients from the bloodstream and send waste substances into the blood. If the blood supply to a section of the omentum is blocked, the cells in the area may die because they can no longer obtain what they need.

terri on October 21, 2016:

how does a person get dead areas as a result of no blood flow to that area in the omentum

Linda Crampton (author) from British Columbia, Canada on November 01, 2013:

Hi, DDE. Thanks for the visit and the comment. The omentum is an interesting part of our body!

Devika Primić from Dubrovnik, Croatia on November 01, 2013:

The Omentum and Abdominal Fat interesting and useful hub about such fat, informative and well pointed out

Linda Crampton (author) from British Columbia, Canada on May 07, 2013:

Thank you very much for the informative comment, Relationshipc. I think that many of us would be shocked if we could see our omentum! A technique that easily and harmlessly allows us to do this would be a great way to encourage weight loss.

Kari on May 07, 2013:

Excellent hub. I would love to see what my omentum looks like right the look of my stomach, I would have to say not very good - probably a lot like that second omentum in the video.

I know that Avian said she was a vegetarian and became lean, but I don't want anyone to think it is that easy. I've been a vegetarian since I was 15 (I'm 35) and my weight has fluctuated between 140 to 190.

There are plenty of unhealthy vegetarian foods - chips, sugar filled foods, fried foods, etc...It's the choices you make about what you eat and how much you eat that helps you keep trim, not the diet itself. Sounds like Avian is making the right choices! :)

Linda Crampton (author) from British Columbia, Canada on April 16, 2013:

Thanks, Nell. I agree - diets don't work for most of us! Even though they may cause weight loss, people often put the weight back on because they can't stick to the diet.

Nell Rose from England on April 16, 2013:

Hi Alicia, I always learn something new when I read your health hubs, I totally agree about not dieting but keeping to a proper food regime, I have tried diets and they just do not work. I never knew about this fat before, fascinating hub, and so useful, nell

Linda Crampton (author) from British Columbia, Canada on April 16, 2013:

Hi, Deb. It's very interesting to hear that that being a vegetarian has kept you lean. (I like my sweets, too!) Thanks for the comment.

Deb Hirt from Stillwater, OK on April 16, 2013:

I like my sweets, I will grant you that, but since I pretty much became a vegetarian, I have become very lean over the past couple ofm years. That, with walking around Boomer Lake, has sure done me a world of good. I have a higher energy level at work better than most of the youngsters there. Great article! I had heard about the omentum, but this piece went into so much more depth.

Linda Crampton (author) from British Columbia, Canada on April 15, 2013:

Thanks for the comment and the votes, sarifearnbd!

Shariful Islam from Bangladesh on April 15, 2013:

Very nicely written hub. Some facts about the omentum. voted up and more!

Linda Crampton (author) from British Columbia, Canada on April 14, 2013:

Hi, MJennifer. Thanks for the visit. I'm experiencing the difficulty in staying slim as the years pass, too! The battle certainly becomes harder as we get older.

Marcy J. Miller from Arizona on April 14, 2013:

This was quite interesting, Alicia. I'm paying a lot more attention to my midsection as I rapidly close in on 50 and have noticed that my perpetually-skinny body from the past is now, sadly, in the past. Everything now seems to go straight to my waistline as it never had before. I need to develop some momentum to reduce my omentum!

Linda Crampton (author) from British Columbia, Canada on April 14, 2013:

Thank you very much for the comment, ytsenoh! I appreciate it. (I don't like the idea of visceral fat building up, either!)

Cathy from Louisiana, Idaho, Kauai, Nebraska, South Dakota, Missouri on April 14, 2013:

Alicia, thanks much for your hub. I have never heard of an "omentum" before, so I learned something new again in the hubs. I agree that we need to develop a healthy eating lifestyle, getting appropriate sleep and incorporating exercise into our daily routine. It's interesting to me that at least for myself, I usually only think about the bigger organs more since I'm not aware of all the medical terms surrounding those organs. Sure don't like the visceral fat part. Thumbs up on your presentation of advice!

Linda Crampton (author) from British Columbia, Canada on April 14, 2013:

Thank you so much for all the votes and the share, vocalcoach. I'm sorry that you have diabetes. I hope the treatment goes well!

Linda Crampton (author) from British Columbia, Canada on April 14, 2013:

Thank you very much for the comment, the vote and the share, shiningirisheyes!

Audrey Hunt from Pahrump NV on April 14, 2013:

I've been recently diagnosed with type 11 diabetes so along with a healthy diet started a walking program. Hope I lose some of my visceral fat :)

Learned some awesome facts here which is why I voted up, useful, awesome, interesting and sharing.

Shining Irish Eyes from Upstate, New York on April 14, 2013:

Great article and very informative. The omentum performs quite of processes...immune system function, T-cell regulator, aiding in tissue repair. The need for optimal omentum and abdominal fat level balance seems quite evident after reading this article. Concise tips and suggestions are appreciated as well.

Voting up and sharing

Linda Crampton (author) from British Columbia, Canada on April 14, 2013:

Thanks for the visit and the comment, Bill. Good luck with the weight loss!

Bill Holland from Olympia, WA on April 14, 2013:

Thank you for the facts and suggestions. Whatever it is called I have about ten pounds of it that I need to lose. :)

Linda Crampton (author) from British Columbia, Canada on April 14, 2013:

Thank you for the comment and the vote, drbj, especially so soon after I published the hub!

drbj and sherry from south Florida on April 14, 2013:

Fascinating facts about the omentum, Alicia. It's particularly interesting to me that scientists may be finding evidence that the omentum does more than simply store fat, and may function in both tissue repair and regeneration. Thanks for the newsflash. Voted up, y'know.