The Role of Visceral Fat in Infertility

Posted by on May 4, 2021 in Infertility
The Role of Visceral Fat in Infertility

Age, weight, BMI…but WAIT, there’s more!!!!!!!! For an extra chocolate cake donut, you can get visceral fat, too!  And, it will also get in the way of your fertility …

Making jokes about being fat is common, but for anyone who has a weight control problem, managing their weight is no laughing matter. Weight control is a major problem for modern society and especially for many patients dealing with infertility. This is particularly true for women with higher BMI’s and the diagnosis of polycystic ovarian syndrome (PCOS). Women with PCOS and insulin resistance (IR) have a metabolic problem. Metabolic problems negatively impact general health including vascular disease, stroke, depression, and type II diabetes. Identifying metabolic problems permits early management of the problem which reduces the lifetime risks. The human body is composed primarily of water (65% of the mass) with lesser contributions by lipids (12%), protein (20%) and other organics, DNA and RNA. If we look at the distribution of water, lipids (fats) and protein, we can use this information clinically to diagnose potential metabolic problems before they create significant health problems. 

Not all Fat is Created Equal

Fat is an important component of health. Body fat, or adipose tissue, is a very complex tissue that has two major types, brown and white. Most body fat is composed of white adipose tissue or white fat. The amount of adipose tissue depends upon numerous reasons, but life habits have a significant impact on the amount and distribution of adipose tissue. Brown fat is used to produce heat, and in many animals, is important for their thermoregulations. In humans, brown fat contains a number of structures in the cell called mitochondria which generate heat. Brown fat may be able to use white fat for energy and it seems as if exercise stimulates brown fat, which may be one way exercise can help reduce the amount of white fat. Brown fat is found primarily in the shoulders and neck of newborns but decreases with age so that most fat in an adult is white fat.

Looking at a group of people it becomes apparent that we come in many different sizes and shapes. The major determinant of how a person is shaped is genetically determined. There are three primary body types: ectomorphs, who are tall and thin with little fat or muscle; endomorphs, who have lots of fat and muscle and tend to gain weight easily and mesomorphs, who are muscular, strong, athletic and can gain or lose weight easily. Superimposed upon these primary body types is the accumulation of white adipose tissue (WAT).  White adipose tissue provides a storehouse of energy that can be mobilized in times of low energy intake. But WAT is a complex tissue. White fat is composed primarily of fat cells (adipocytes) but contains a number of other cells and tissues in the form of blood vessels nerve fibers, lymph vessels, immune cells, and pre-adipocytes. Many of these cells secrete bioactive substances into the blood system making fat an active participant in the metabolic maintenance of the body. WAT produces cytokines, growth factor, and adipokines. These substances affect insulin action and impact appetite and activity. The primary function of white fat is to provide an energy storage depot so that in times of decreased calorie intake, the energy in fat, in the form of fatty acids, can be mobilized. Many hormones and substances regulate the storage or mobilization of energy in fat. For example, glucagon, growth hormone, and cortisol all promote fat mobilization while insulin promotes fat storage moving glucose out of the blood stream and into fats cells to be converted to storage glycogen. The amount of fat that is created is influenced by a number of factors that regulate appetite and exercise.

Fat…Inside and Out

White adipose tissue can be divided into subcutaneous WAT (SAT) or visceral WAT (VAT). SAT is found under the skin and provides a cushioning effect. SAT is found primarily in the shoulders, hips, and thighs. VAT is found primary in the abdomen around the omentum, kidneys and mesentery. SAT and VAT have a similar appearance and thus they have been considered equal in function. However, it seems that the amount of VAT correlates with increased health risks especially insulin resistance. One way used to distinguish the function of SAT from VAT involved the use of mouse tissue transplantation experiments. SAT from obese mice was transplanted into the abdomen and actually proved beneficial. The mice lost weight and reduced the insulin resistance. However, when VAT was removed, reducing the amount of VAT, the metabolic complications of obesity were reduced. Interestingly, the fat cells of VAT and SAT, called adipocytes, differ with SAT having smaller cells but VAT has fat adipocytes. As in the body as a whole there are skinny and fat fat cells. The SAT adipocytes take up glucose and are responsive to insulin. But the fat VAT cells do not demonstrate an increase in glucose uptake when expose to insulin- they are resistant. 

Some people are obese but metabolically healthy and they seem to have more SAT. One study estimated the amount of VAT in a group of overweight patients using a number of methods to estimate the percentage of visceral fat. They found that the group that had a pathological amount of visceral fat had an 81% incidence of insulin resistance. The group that did not have a pathological amount of visceral fat had a 33% incidence of insulin resistance. So, even the overweight group with lower amounts of VAT still had one out of three patients with insulin resistance. One way in which SAT differ from VAT is that SAT has immune cells which make it anti-inflammatory. However, VAT is just the opposite with an increase in inflammatory cells and production of inflammatory substances. The increased inflammatory profile of VAT results in increased insulin resistance. Bottom line: More VAT, more insulin resistance. Increased insulin resistance, longer times to pregnancy.

How to Tell and What to do?

The importance of VAT as contributing to metabolic pathology, especially insulin resistance, generates the need to be able to accurately measure the amount of visceral fat. Your BMI (body mass index which is a measure of obesity) does not distinguish SAT from VAT. Since VAT accumulation occurs primarily in the abdomen, measuring the abdominal circumference increases the accuracy of determining the amount of VAT. Performing a waist to hip ratio provides an even better estimate of visceral fat. All of these measurements can be done easily in the clinic and compared to measurements of standards that have been constructed. Skin fold measurement can also be useful and are easily done in a clinic setting. It is seldom necessary to have better estimates of the percent VAT; however, DEXA scan, underwater weighing, MRI, and CT can also be used should the need arise for more accuracy. A popular, easily done measurement is bioelectrical impedance (BI). There are commercially available scales, both for the home and more sophisticated for gyms and clinics that are helpful when a person is trying to reduce the amount of VAT.

For people who are overweight, sorry to say, there is no easy way to reduce visceral fat. However, exercise and eating a healthy diet will go a long way to reduce visceral fat. More importantly, new studies on weight and infertility show that weight loss has a positive impact on insulin resistance and achieving a pregnancy. There have been volumes written about weight loss, but the bottom line is that to lose weight there needs to be calorie restriction (especially limiting carbohydrates). How you choose to do this is not nearly as important as just doing it – so, trying counts! A weight loss of even 10 % is frequently sufficient to permit a more normal functioning metabolic system and reduce the risk from insulin resistance. In a nutshell: Lose 10% of your body weight and you could shorten your time to achieving a pregnancy.

Setting realistic goals, engaging a support system, and remembering the purpose will help increase your chance for a successful pregnancy…and a healthier lifestyle overall.