Written by Brian Rigby, well-known to our readers from his previous post on chronic inflammation and ways to combat it. Reviewed by Dov Michaeli, MD, Ph.D.

The time when fat was considered to be a simple storage organ has passed. Though storage is by far the most visible aspect of fat, we know now that even “storage fat” has incredibly diverse functions and, in reality, is a part of our endocrine system, the system of hormone-releasing glands which regulate everything from our moods and metabolism to growth and sexual function.


There are MANY types of fat in your body

Fat is also not so uniform as the catch-all term would imply—it exists in many forms in our body, some of which are extremely vital, useful, and not prone to expansion in the same way other forms of fat are. The fat which is prone to expansion comes in two forms: subcutaneous (“under the skin”) and visceral (also known as belly fat). While both these fats accumulate in areas which can be seen and felt, it’s the less visible effects of belly fat which make it so important to get rid of!


An overview of the two visible types of fat

While both types of fat serve as a storage area for excess energy, they differ somewhat in the other functions they serve and their overall impact on health. Subcutaneous fat is the type found visibly in most areas of the body, such as the butt, thighs, and arms. It may be visible, but the good news is that compared to belly fat, it does not carry much of a health risk. Subcutaneous fat can also be found on the belly (superficial to the ab muscles), though the fat which gives people a “gut” tends to be belly (visceral) fat, even if there is excess subcutaneous fat in that region as well.


Why too much belly fat is dangerous

Belly fat is the fat which serves to pad our internal organs from shock and is found underneath the abdominal wall (under the ab muscles). While a certain amount is necessary, too much is a serious health risk, as it turns up the production of certain hormones and pro-inflammatory cytokines (hormone-like messengers).

By increasing the amount of pro-inflammatory messenger activity, inflammation in the body rises, leading to a number of health issues including chronic diseases like heart disease and even cancer. Increasing the release of hormones can also inadvertently make it harder to lose weight, as hunger becomes less well-regulated and you are more prone to cravings even when you are not in need of food.


The good news is that belly fat is easily burned

The good news is that belly fat is more easily burned than subcutaneous fat, making it possible to lose it faster and improve health and other risk-factors quickly. Before we concentrate on how to lose the belly fat, however, why we accumulate belly fat in the first place should be examined.


Why do we get belly fat?

Beyond gender (men are more prone to belly fat than women) and genetics, one of the leading causes of belly fat is increased insulin resistance. Insulin resistance, in a nutshell, is when your body no longer responds to insulin at an appropriate level, leading the body to release ever-increasing amounts of the hormone in an attempt to get the muscles, fat, and liver to take it up.

Why does this happen? The most common reason is diet, especially diets high in fat and refined sugar and low in fiber.  In a study featuring both healthy and overweight people, diets high in fat (but not omega-3 fats, it should be noted) caused decreased insulin sensitivity, even in the otherwise healthy participants. When you eat a high-fat diet, your blood becomes loaded with free fatty acids, destined either for use by the muscles or storage as fat.


When you reduce sugar, fat becomes a GREAT source of energy

This is not always a bad thing, as free fatty acids can be a wonderful source of fuel for your muscles, but only if you are currently in need of it (such as when you are exercising). Unfortunately, our body has learned to respond to this increase in free fatty acids in a way that, while beneficial if exercising, is less ideal in other situations.


Why exercise burns fat

Glucose is the prime fuel for our brain, and it demands that it has preference over all glucose reserves, no matter how much is available. When we are sedentary and well-fed, there is plenty of glucose so the brain lets other organs use it as well. When we exercise, however, our brain starts to horde that fuel for itself. Our body reacts by releasing an alternate fuel for the muscles: free fatty acids. The muscles then react by turning down their glucose-transporters to help save the glucose for the brain and to better utilize the fat.


Why sugar prevents belly fat from being burned

Insulin, on the other hand, works by turning up the glucose-transporters found in your cells, so it is actively antagonized by excess free fatty acids. When you are starving or exercising, insulin is naturally low, so it won’t fight the free fatty acids. After we have eaten, however, insulin is released in larger amounts to help control the elevated blood sugar from the meal.


Why high-fat diets prevent belly fat from being burned

If that meal was a high-fat meal, then the blood also becomes loaded with free fatty acids, which work against the insulin causing the pancreas to release even more insulin to achieve the proper effect. It’s interesting that excess sugar creates essentially the same problem, and that it is not the blood glucose, itself, which appears to be the direct problem. Rather, the problem with excess sugar is that it too will cause the blood to be loaded with fatty acids, which over time can contribute to insulin resistance. While sugar may not be the direct agent in the formation of insulin resistance, it should be noted that control of blood glucose is the direct victim once insulin resistance sets in.


How fructose prevents belly fat from being burned

Of even more worry than glucose in the modern diet is fructose. Most refined sugars contain a significant portion of fructose in addition to glucose. Many people revile high-fructose corn syrup as being a great evil in the world of food, but the truth is that even regular table sugar is 50% fructose (the aforementioned high fructose corn syrup is 55% fructose, a scant 5% higher—realistically speaking, table sugar is just as bad). Agave nectar is even worse, running as high as 85% fructose in some batches! As with fat, fructose is not truly the enemy here—overconsumption of that sugar is. The issue with fructose is that our body cannot use it directly as energy, vastly preferring glucose as its sugar fuel source. While glucose will begin circulating in the blood almost instantly after absorption, providing energy to our brain, muscles, and other organs, fructose gets metabolized by the liver instead, first into glycogen (a form of short-term storage), if it is needed, and then into fat.

Key point: If too much fructose is consumed at once, our liver is overloaded, and more fructose will end up as fat.

Further reading on related topics: Is Sugar Carcinogenic? and What’s Up with Fructose?

Click here to read Part 2. The original article was first published on the PEERtrainer website.

Dov Michaeli, MD, PhD
Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.