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Belly Fat Breakthrough Chapter 1
Understanding Belly Fat
Americans are getting fatter and more obese. Two thirds of adults (66 percent) are currently overweight or obese.1 A third of adults (36 percent) are currently overweight. This is true in a majority of the developed world, such as Australia and Europe. Australia now has the second highest rate of childhood obesity, while in the United Kingdom, the number of obese adults increased from 16 percent to 24 percent among women and from 13 percent to 22 percent among men between 1993 and 2009. There is also potential for a dramatic increase in obesity rates in India, the Middle East, Asia, and other developing areas, as overweight and obesity rates there have escalated since the 1990s.2
We’re also seeing a rise in dangerous belly fat, as demonstrated by the increase in average waist circumferences around the world. Having a waist circumference less than 31 inches for women and 37 inches for men is recommended for health reasons, but in the United States, the average waist circumference went from 35 inches in 1962 to 39 inches in 2000 in men, and from 30 inches to 37 inches in women.3 Another US study monitored more than one hundred thousand middle-aged men and women over nine years. Results showed that people with large waists—greater than 47 inches for men and 43 inches for women—were twice as likely to die prematurely as those with normal waist sizes.4 In the United Kingdom, a 2011 study found that the average waist circumference of young girls, 28 inches, was 5 inches bigger than girls of the same age measured thirty years previously.5
As world levels of belly fat increase, so does the incidence of both type 2 diabetes and cardiovascular disease, so it’s important that we understand why we are putting on belly fat and how we can stop this trend.
The Skinny on Fat
We have a layer of fat under the skin called subcutaneous fat. This fat makes up about 80 percent to 90 percent of our total body fat and is typically located on the back of the arms, below the shoulder blades, around the belly, and on the upper legs and hips. The remaining 10 percent to 20 percent of our body fat is termed belly fat, also known as visceral fat, and is located beneath the stomach muscles and around internal organs such as the liver, spleen, intestines, and kidneys. In some people, belly fat can also accumulate in the liver and other organs. Interestingly, people with more fat on their upper thighs have less incidence of type 2 diabetes and cardiovascular disease.6
Subcutaneous fat serves a number of purposes, such as keeping us warm and acting as a storage site for hormones and energy. Also called adipose tissue, it used to be considered mainly a ready source of energy in times of famine, but fat is now viewed as an endocrine organ that stores and excretes a number of hormones and other chemicals that can have both positive and negative effects on health. Endocrine refers to cells, glands, and tissues that secrete hormones into the bloodstream to control our physiology and behavior. Fat mass secretes over thirty chemical messengers; some of them, such as the hormone leptin, tell the brain that we have had enough to eat, whereas others, like tumor necrosis factor, induce inflammation to help combat bacteria, viruses, and other disease-producing pathogens.
Too much inflammation, however, results in cardiovascular disease and insulin resistance. The latter condition occurs when the muscle and liver cells become unresponsive to insulin in the blood. High levels of insulin and glucose remaining in the circulation increase the risk of type 2 diabetes. People with type 2 diabetes typically have excessive belly fat, chronic high blood pressure, or hypertension, and elevated blood triglyceride levels. Fat cells also secrete a chemical called adiponectin, which has antidiabetic properties. Unfortunately, obese people have less of this beneficial chemical.
We all possess billions of fat cells, but it has been shown that an absolute fat cell number is established during the teenage years, and this remains constant during adulthood. One study that assessed genomic DNA was able to retrospectively measure fat cell numbers in humans.7 A genome is a body’s total set of DNA and includes all its genes. Each genome contains all the information needed to create and maintain a human body. Both obese and lean children established their peak fat cell numbers during adolescence, with little change occurring during adulthood. Importantly, those who became obese during adolescence possessed billions more fat cells than their leaner counterparts. As the fat cell lasts about eight to ten years before dying, a natural process known as apoptosis, any extra fat cells that children develop increase their fat-storage capacity, which leads to obesity, and overweight teenagers will therefore have those billions of extra fat cells for the rest of their lives.
Belly fat is different from subcutaneous fat and is much more dangerous, as it contributes to type 2 diabetes and cardiovascular and inflammatory diseases.8 As can be seen in figure 1, belly fat lies underneath the tummy muscles. Because belly fat is firmer than subcutaneous fat, it pushes the abdominal muscles outward. These fat cells, residing deep in the abdomen, do not release their free fatty acids into the bloodstream but deliver them straight to the liver. In response, the liver produces other forms of fat, called triglyceride and cholesterol, which are then secreted into the circulation. When fat in a fat cell is broken down and transported into your blood, it is referred to as free fatty acid, whereas triglyceride is also a type of fat found in the blood and is used by the body for energy. High triglyceride and cholesterol levels are associated with increased risk of cardiovascular disease.
Belly fat cells also have a greater blood supply than subcutaneous fat cells do, and thus can release fatty acids and hormones far more quickly. The good news is that, compared with subcutaneous fat cells, belly fat cells are far more responsive to circulating catecholamines. These are the major hormones for promoting fat release and fat burning, and they can be significantly elevated by interval sprinting exercise, as discussed in chapter 3. This means that belly fat is easier to lose than subcutaneous fat.
How Belly Fat Accumulates
Belly fat accumulation is influenced by a number of factors, such as possessing high levels of fat-storing hormones and low levels of fat-burning hormones; being sedentary; and having a genetic predisposition to developing belly fat. Eating too much processed food is also related to increases in belly fat and is covered in more detail in chapter 4. Other factors affecting belly fat development accumulation include age, ethnicity, and lifestyle.
Figure 1. Abdominal stores of subcutaneous and belly fat (visceral fat)
Cortisol, a hormone that is secreted into the blood by the adrenal gland atop each kidney, is typically elevated during moments of stress. When blood cortisol levels increase, the amount of sugar in the blood also increases, which results in a corresponding rise in insulin. Having elevated levels of cortisol and insulin in the blood encourages fat storage and impedes fat burning. This means that high levels of stress increase the concentrations of the two hormones, leading to reduced fat release and increased belly fat stores. Cortisol may also contribute to leptin resistance, which means that people eat more, since fat cells discharge the satiety hormone to tell the brain we are full.
The catecholamines are epinephrine (or adrenaline) and norepinephrine (or noradrenaline) and are secreted into the blood by the adrenal glands. Norepinephrine is also released at nerve endings. Blood catecholamine levels gradually increase through the night and typically peak around eleven o’clock in the morning. Catecholamine-induced fat mobilization occurs much more in belly fat than in subcutaneous fat.
Unfortunately, this catecholamine-induced release of fat is suppressed in obese individuals. This suppression occurs at a young age, as it is present in obese teenagers and children, whose mobilization of triglyceride stores by epinephrine was decreased by 30 percent during rest. This inability to mobilize lipids increases the amount of fat depots in our bodies and can lead to abdominal obesity. Its cause is undetermined but appears to be influenced by defective fat cell receptors. Receptors are specialized proteins located on the outside of cells that allow communication between the cell and the body. Another fat-burning hormone is growth hormone, which is produced by the brain’s pituitary gland. Insulin slows down growth hormone release, so people with high levels of insulin in their blood typically have lower levels of growth hormone. Having problems with the thyroid gland can also result in increased belly fat accumulation. The thyroid, an endocrine gland located at the base of the neck, releases a hormone called T-3 (thyroid hormone), which elevates our metabolic rate. Metabolic rate is the amount of energy expended daily at rest. In addition, together with catecholamines and growth hormone, it prompts cells to release more fat. Hypothyroidism occurs when the thyroid gland produces too little T-3 or cells’ T-3 receptors become insensitive. Low thyroid levels can contribute to elevated fat deposition and can cause an increase in belly fat stores, and they are often accompanied by elevated low-grade inflammation, as hypothyroid individuals have been shown to possess increased levels of Creactive protein, an inflammatory chemical, in their blood.
Over the past three decades, researchers have discovered genetic markers that contribute to increased body weight and waist circumference; however, no single gene has been found to cause obesity. A genetic marker is an altered gene or DNA sequence that indicates an elevated risk of developing a specific disease or health problem. Specific genes related to obesity have been identified; among them are a number of single-gene mutations that play a part in the development of obesity in teenagers and young adults. This means we now know that genes affect belly fat development when influenced by factors such as physical inactivity, nutrient intake, and metabolic status.
Lifestyle Factors That Influence Belly Fat Accumulation
Many lifestyle factors impact belly fat, but perhaps the most important (after diet and exercise) are age, drinking alcohol, ethnicity, smoking, stress, and sleep. Exposure to daily stressors and reduced quality of sleep have both been associated with belly fat accumulation. Chapter 5 covers how poor sleep and uncontrolled daily stress can lead to belly fat development, together with a description of stress-management and sleep-enhancing techniques.
People who do not take part in recreational exercise and have little physical activity in their jobs are prone to belly fat accumulation, especially if they consume a lot of processed food. Exercising burns up energy and gradually makes the body metabolize more fat than carbohydrate. Carbohydrates are found in fruits and are broken down by the body to be used as energy. They are also present in unhealthy processed foods such as sugar and white bread. It is also likely that fat burning continues during the period after exercise. See chapter 2 for a discussion of how different forms of exercise have differing effects on body fat and muscle mass.
Genes play a role in aerobic fitness levels, and estimates of their contribution to such fitness vary between 10 percent and 40 percent. If you have parents who were good at activities such as cross-country running, it is likely that you will carry genes that will make you good at performing aerobic running exercise. However, all kinds of fitness are influenced mainly by exercising, and to keep fit, you need to perform physical activity. Medical professionals called exercise physiologists assess people’s aerobic fitness by exercising them to exhaustion on a bike or treadmill and measuring their maximum oxygen uptake, which reflects aerobic fitness. Determining maximum oxygen uptake, however, requires expertise and expensive equipment. An easier way of assessing aerobic fitness is to see how far you can walk or run on level ground in twelve minutes. This test, the Cooper Twelve-Minute Walk/Run Fitness Test, is described in appendix A, on page 183. For endnote see 1, page 219.
On page 15 you’ll find a questionnaire assessment that does not involve exercising. If you score 9 points or less on the questionnaire, or walk or run less than 0.6 miles on the walk/run fitness test, it is likely that you are really unfit and need to begin a fitness program.
Older people tend to have more belly fat than young people. The main reason for this seems to be a decrease in the body’s metabolism: after the age of thirty, most people’s metabolism diminishes about 1 percent every two years. Why metabolism slows down as we age is unclear, but it probably involves a decrease in muscle mass and a change in hormone levels. While the amount of subcutaneous fat generally declines with aging, so does muscle mass, and since skeletal muscles, together with the liver, are the major fat-burning engines of the body, older people burn lower levels of fat overall.
The decrease in muscle mass with aging, however, is not inevitable, as people who perform regular weight training typically retain most of their muscle mass and ability to lift weights. Thus, most people see their muscle mass deteriorate as they grow older simply because they are not challenging their skeletal muscles regularly. The good news is that interval sprinting exercise can significantly increase muscle mass.
As we age, blood hormone levels can decrease because of reduced secretion by the body’s endocrine glands. The receptors on the body’s cells can become insensitive and don’t respond to hormones effectively. For women, the largest hormonal change concerns reduced estrogen production when they enter menopause, whereas for men, the largest hormonal change typically involves reduced testosterone.
Alcohol contains 7 calories per gram, which is more than the 4 calories contained in a gram of carbohydrate and protein and just under the 9 calories per gram of dietary fat. A calorie is a unit of energy and refers to energy consumption generated by eating, drinking, and physical activity. Thus, consuming two to three average-sized alcoholic drinks a day adds up to over 500 calories. In a week, over 3,500 extra calories would be consumed. Since 1 gram of fat equals 9 calories, that means having three drinks every day of the week adds almost 400 grams of fat to your diet. According to studies in this area, the majority of these calories appear to be deposited as belly fat. It has also been shown that drinking alcohol makes people hungry.
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