Fat in our body and in our diet has a number of important roles. I decided to write this chapter because there is a great deal of confusion about fat, and many diets and exercise programmes are designed around this subject, which can be harmful to health and wellness. I hope this chapter will help to demystify the subject.
IMPORTANT ROLES OF FAT IN OUR BODY
Provision of energy
Although carbohydrates form the main source of energy for our bodies, fat is a source of backup energy, when carbohydrates are not readily available. One gram of fat has nine calories, compared with four calories per gram of carbohydrates and proteins, and seven calories per gram of alcohol.
Helps absorb and store fat-soluble vitamins
Certain vitamins require fat as a carrier to be absorbed into the body. These are known as ‘fat-soluble vitamins’. They are also stored in the fat in the body. These include vitamins A, D, E and K, which are essential for a healthy body and immune and circulatory system.
Energy storage
Consumption of food surplus to the body’s needs is stored in the form of fat. Fat stores are found under the skin. Fat is also deposited around organs and this can act as energy storage too.
Insulation
Fat acts an insulation under the skin, maintaining the internal temperature. The deeper skin layers then insulate the core against extreme temperature changes. It also has a thermogenic effect: this is where it can generate and release heat when our skin temperature drops significantly.
Protection
Fat is organised to form cushions around major organs, to act like shock absorbers and protective pads.
Detoxification
Body fat helps to eliminate, store and excrete toxins and certain drugs from the rest of the body.
Hormonal function
Fat cells regulate the production of the sex hormones, particularly oestrogen. Fat is also a component of prostaglandins (hormones produced by individual cells), which have a regulatory role in the body, particularly on platelets and clotting; the uterus, in regulating conception, pregnancy and labour; in modulating the immune system and the inflammatory response; controlling fluid transfer in the guts; controlling electrolyte balance in the kidneys; controlling blood pressure and in the metabolism of fat. They also have a role in the transmission of pain, controlling intraocular pressure in glaucoma, regulating the movement of calcium, controlling cell growth, producing fever during an infection, inhibiting acid production and increasing libido. They can also cause constriction and dilatation of the airways. As you can see, these are one of the most crucial substances found in the body, with hormone-like and regulatory functions on the body’s systems.
Cellular health and integrity
Fat is an essential part of the cell membrane (wall), which plays an important role in keeping each cell healthy and functioning correctly.
Brain and nervous system
Fat forms the structural components of the brain and the nervous system. It is the basis of the myelin sheath, which helps transmit the nerve signals quickly.
Maintenance of mood
Fat in our diet releases endorphins, which stimulate the pleasure centres. It also enhances the taste of food that we eat.
THE STORY OF FAT
The distribution of fat in the body is determined by our genetics. The number of fat cells in our bodies is determined by our diets during childhood, and once set, the number and type of fat cells remain the same throughout life. The amount of fat stored in our fat cells is then determined by our surplus calorie intake and hormonal action, particularly after the age of thirty-five.
Below thirty-five our metabolism and health is mainly driven by our genetic blueprint. After the age of thirty-five, which I refer to throughout as the ‘Tipping Point’, our environment and lifestyle has a greater role on our metabolism, weight and health. This is related to our cellular health.
We know that cells become less efficient with age, which is partly due to hormonal changes, and partly due to our environment, which includes free radical damage, toxic damage, poor nutrition and inefficient fuel usage by the cells, i.e. carbohydrates. There produce toxic end products and free radicals as a by-product of metabolism rather than medium chain fatty acids, which are a much cleaner source of fuel for cells.
THE HORMONES THAT AFFECT FAT METABOLISM
Insulin – known as the number 1 fat storer Insulin is strongly influenced by foods that increase blood sugar. Blood sugar is toxic and about 90 per cent is removed from the blood in two minutes, and stored as glycogen or fat by insulin. A persistently poor diet, with overconsumption of calories such as carbohydrates, fats or protein – which chronically stimulates the release of insulin – will eventually lead to insulin resistance and ultimately results in the development of metabolic syndrome and diabetes. Insulin resistance results in high levels of insulin, which inhibits the fat-burning effects of other hormones.
Glucagon – known as the number 1 fat burner Glucagon has the opposite effect to insulin, but is inhibited by chronically high levels of insulin. By controlling insulin levels, we can allow glucagon to do its work and help burn fat.
Ghrelin and Leptin – known as the hunger hormones These work to increase and decrease appetite. Both respond to dietary and exercise stress so we can manipulate them and control our weight gain or loss without resorting to potentially harmful slimming drugs and supplements.
Ghrelin – the hunger hormone that increases appetite This peptide hormone (considered to be a growth hormone releasing peptide, or GHR) is secreted by the stomach and sends signals to the brain that causes you to feel hungrier. Its levels rise before and drop after meals. It is therefore a fast-acting hormone. Ghrelin has metabolic effects, in that it controls insulin and leptin sensitivity (resulting in insulin and leptin resistance); it also stimulates growth hormone and growth peptides. In cases of a dilated stomach the secretion of ghrelin becomes excessive and out of control because the stomach stretch response is lost, which means that it overrides the signals from the gut to the brain that tell you to stop eating (satiatory response). It has been shown to play a role in short-term feeding and long-term weight gain. Ghrelin can be seen as a ‘gremlin’ that plays havoc with other hormones and the body’s metabolism by influencing:
1 Regulation of growth hormone, insulin and leptin secretion and sensitivity
2 Glucose and lipid