WHAT IS FAT?
Dietary fats are divided into two categories, the generally unhealthy saturated fats and healthy unsaturated fats. Both are built with fatty acids. What makes them saturated or not has to do with whether or not all the places for a hydrogen atom in their structure are filled or not. Saturated are full. Unsaturated are not.
Before we get into the two kinds of dietary fat and which foods have them, there is another fat term you might be wondering about: essential fatty acids.
Much of the fitness world is afraid of fat, yet there is often little understanding of what fat is or how it fits into a healthy lifestyle. In this introduction to dietary fat, we are going to answer the question, What is fat?, explain unhealthy and healthy fats, look at how fat calories put excess fat our bodies, and, yes, reveal the benefits of fat.
Dietary fats, provided they aren’t contaminated by the toxins fats can store, have many have benefits — except trans-fats which have no benefits to health at all.
Fat is a major source of energy in the diet. Dietary fat contains nine calories per gram, which is more than twice the number provided by carbohydrates or protein. Due to its high caloric content , the chance of becoming obese increases with a high intake of fat.
Some fat is essential to proper body function. Fat fills adipose tissue that helps to insulate the body. Fat helps the body absorb certain vitamins.
Healthy skin and hair are also maintained by fat.
Some types of fat (saturated and trans fats) raise blood cholesterol and can increase heart disease risk. A diet high in saturated fat causes cholesterol to build up in the arteries. Unsaturated fats do not raise blood cholesterol and they may help to lower cholesterol if used in place of saturated fats.
Examples: Fat helps the body absorb fat-soluble vitamins, such as vitamin A.
BENEFITS OF FATS:
- Slow digestion
- Make you feel full
- Slow absorption of carbohydrates in the intestine
- Hormone production and balance
- Improve mood
- Absorb fat soluble vitamins – A, D, E, K
- Keep you oiled — hair, skin, joints, brain
- Reduce inflammation
- Emulsify (breakdown and move) fats
- Brain health
- Source of energy
Of course there are different kinds of fats and some are more healthful than others. To understand that, let us do a very quick fat-science lesson. Don’t worry, it’s easy and you will be able to make better choices about the fats you buy and put in your mouth if you get a few key concepts.
ESSENTIAL FATTY ACIDS (EFAS) – THE BUILDING BLOCKS
Saturated and unsaturated fats are built with molecules that are made of 3 fatty acids (hence the term triglycerides) and a glycerol molecule. The fatty acids your body cannot make for itself are called essential fatty acids. The omega-3 fatty acids you may have heard are so healthful are in that category. Those, along with omega-6 fatty acids, must be taken in through diet. The problem is that American diets are usually overly abundant in omega-6 and lacking in Omega-3 fatty acids, which is why people are currently urged to include omega-3 sources in their diets such as cold water fish, flax, green leafy vegetables, and nuts or use omega-3 supplements.
FATS AND CHOLESTEROL
It’s time to end the low-fat myth. That’s because the percentage of calories from fat that you eat, whether high or low, isn’t really linked with disease. What really matters is the type of fat you eat.
- Choose foods with healthy fats, limit foods high in saturated fat, and avoid foods with trans fat.
- “Good” fats—monounsaturated and polyunsaturated fats—lower disease risk. Foods high in good fats include vegetable oils (such as olive, canola, sunflower, soy, and corn), nuts, seeds, and fish.
- “Bad” fats—saturated and, especially, trans fats—increase disease risk. Foods high in bad fats include red meat, butter, cheese, and ice cream, as well as processed foods made with trans fat from partially hydrogenated oil.
- The key to a healthy diet is to choose foods that have more good fats than bad fats—vegetable oils instead of butter, salmon instead of steak—and that don’t contain any trans fat.
THE LOW-DOWN ON LOW-FAT
“Low-fat,” “reduced fat,” or “fat-free” processed foods are not necessarily healthy. One problem with a generic lower-fat diet is that it prompts most people to stop eating fats that are good for the heart along with those that are bad for it. And low-fat diets are often higher in refined carbohydrates and starches from foods like white rice, white bread, potatoes, and sugary drinks.
- When food manufacturers take out fat, they often replace it with carbohydrates from sugar, refined grains, or starch. Our bodies digest these refined carbohydrates and starches very quickly, causing blood sugar and insulin levels to spike and then dip, which in turn leads to hunger, overeating, and weight gain.
- Over time, eating lots of “fast carbs” can raise the risk of heart disease and diabetes as much as—or more than—eating too much saturated fat.
So when you cut back on foods like red meat and butter, replace them with fish, beans, nuts, and healthy oils—not with refined carbohydrates.
Although it is still important to limit the amount of cholesterol you eat, especially if you have diabetes, for most people dietary cholesterol isn’t nearly the villain it’s been portrayed to be. Cholesterol in the bloodstream, specifically the bad LDL cholesterol, is what’s most important. And the biggest influence on blood cholesterol level is the mix of fats and carbohydrates in your diet—not the amount of cholesterol you eat from food.
FOOD SOURCES OF SATURATED FAT
Pizza and cheese are the biggest food sources of saturated fat in the U.S. diet, and other dairy products and meat products are also are also major contributors. Keep in mind that all foods contain a mix of fats. Even “healthy” foods like chicken, fish, nuts, and oils do contribute some saturated fat to the diet, though they are much lower in saturated fat than beef, cheese, and ice cream. And it would be a mistake to cut back on nuts, oils, and fish to minimize saturated fat.
As a general rule, it’s a good idea to keep your intake of saturated fats as low as possible. We can’t eliminate saturated fat from our diets completely, because foods that are good sources of healthy fats—olive oil, peanuts, salmon—also contain a little bit of saturated fat. Since red meat and full-fat dairy products are among the main sources of saturated fat in our diets, keeping these foods low is the best way to reduce intake of saturated fat. And when you cut back on red meat and dairy products, replace them with foods that contain healthy fats—fatty fish like salmon, nuts and seeds, plant oils, avocadoes—not with foods that are high in refined carbohydrates. Here is a table showing the top food sources of saturated fat in the American diet.
WHAT IS SATURATED FAT?
Saturated fat is a type of fat in food. Due to its chemical structure, it is usually hard at room temperature. Saturated is found in significant amounts in animal foods, such as the visible fat on meat and chicken, butter, cream and full fat dairy products, and in plant foods like palm and coconut oil.
WHY SHOULD I REDUCE SATURATED FAT IN MY DIET?
Currently, Australians are eating more saturated fat than the recommended intake of 10% of total energy intake or less. The Heart Foundation recommends for heart health that saturated fat be reduced to 7% of total energy.
Saturated fat increases blood cholesterol, in particular LDL cholesterol (the ‘bad’ type). Replacing saturated fat with unsaturated fat reduces the risk of heart disease.
According to the 2011/12 National Nutrition Survey, the top three sources of saturated fat in the Australian diet are:
- Milk and dairy products (including foods like ice-cream)
- Biscuits, cakes and pastries
- Meat, and poultry (including processed meats)
FIVE QUICK TIPS TO REDUCE THE AMOUNT OF SATURATED FAT IN YOUR DIET:
- Limit foods like cakes, biscuits, pastries and savoury snacks. These foods are termed ‘discretionary foods’ and are foods that should be limited sometimes and in small amounts. Cakes, pastries, biscuits, pizza, hamburgers and hot chips are one of the main sources of saturated fat in our diets.
- Swap full fat dairy foods for reduced, low or no fat dairy foods for all family members more than two years old. You will remove 4 kg of saturated fat from your diet in a year if you do this with 1 cup of milk, two slices of cheese and a small tub of yoghurt a day. You can remove even more by choosing no fat foods.
- Swap butter for a margarine spread made from canola, sunflower, olive or dairy blends. Just doing this with your morning toast and sandwiches at lunch will remove 2.85 kg of saturated fat from your diet in one year.
- Cut the fat. Trim all visible fat from meat, remove skin from chicken and try to avoid processed meat (e.g. sausages and salami). Look for products that have the Heart Foundation Tick.
- Eat two to three serves of oily fish a week. A serve of fish is 150 g, which is about the size of your whole hand. Including fish two to three times a week instead of meat or chicken is a simple way to reduce saturated fat in the diet while getting the added benefits of omega-3. Add fish oil capsules and omega-3 enriched foods and drinks to your diet if you’re not eating enough oily fish.
HEALTHY HEART TIP
Lean meat can be more expensive but keep in mind that when purchasing regular mince you purchase the meat and the fat, but with lean mince you are just buying the meat. Try using a smaller amount of lean meat and boost the nutrition by bulking up your meaty dishes with a can of red kidney beans, lentils or vegies.
FUNCTIONS OF FATS IN THE BODY:
1. The main function of fats in the body is to provide energy: By supplying energy, fats save proteins from being used for energy and allow them to perform their more important role of building and repairing tissues. Fats on oxidation provide almost twice as much energy as that given by carbohydrates.
The fats provide on oxidation about 37 kJ of energy per gram as compared to 17kj of energy per gram of carbohydrates. Fats yield more energy than carbohydrates because fats contain less percentage of oxygen and higher percentage of carbon and hydrogen as compared with carbohydrates.
Fats can also be stored in body for subsequent use. When we consume food which has more energy than is required by the body for performing various functions, the excess food is deposited under our skin in the form of subcutaneous fat.
2. In addition to supplying energy, fats also help in forming structural material of cells and tissues such as the cell membrane.
3. Fats also carry the fats soluble vitamins A, D, E and K into the body and help in the absorption of these vitamins in the intestines.
4. Some fats supply essential fatty acids.
THE ROLE OF DIETARY FAT
Dietary fat is frequently undervalued as a contributor to health and performance of athletes. Fat is an extremely important fuel for endurance exercise, along with carbohydrate, and some fat intake is required for optimal health. Dietary fat provides the essential fatty acids (EFA) that cannot be synthesized in the body.
The fat stores of the body are very large in comparison with carbohydrate stores. In some forms of exercise (e.g., prolonged cycling or running), carbohydrate depletion is possibly a cause of fatigue and depletion and can occur within 1 to 2 hours of strenuous exercise (see chapter 6). The total amount of energy stored as glycogen in the muscles and liver has been estimated to be 8,000 kJ (2,000 kcal). Fat stores can contain more than 50 times the amount of energy contained in carbohydrate stores. A person with a body mass of 80 kg and 15% body fat has 12 kg of fat. Most of this fat is stored in subcutaneous adipose tissue, but some fat can also be found in muscle as intramuscular triacylglycerol (IMTG). In theory, fat stores could provide sufficient energy for a runner to run at least 1,300 km. Ideally, athletes would like to tap into their fat stores as much as possible and save the carbohydrate for later in a competition. Researchers, coaches, and athletes have therefore tried to devise nutritional strategies to enhance fat metabolism, spare carbohydrate stores, and thereby improve endurance performance. Understanding the effects of various nutritional strategies requires an understanding of fat metabolism and the factors that regulate fat oxidation during exercise. This chapter therefore describes fat metabolism in detail and discusses various ways in which researchers and athletes have tried to enhance fat metabolism by nutritional manipulation. Finally, the effects of both low-fat and high-fat diets on metabolism, exercise performance, and health are discussed.
FAT METABOLISM DURING EXERCISE
FAs that are oxidized in the mitochondria of skeletal muscle during exercise are derived from various sources. The main two sources are adipose tissue and muscle triacylglycerols. A third fuel, plasma triacylglycerol may also be utilized, but the importance of this fuel is subject to debate. Figure 7.1 gives an overview of the fat substrates and their journey to the muscle. Triacylglycerols in adipose tissue are split into FAs and glycerol. The glycerol is released into the circulation, along with some of the FAs. A small percentage of FAs is not released into the circulation but is used to form new triacylglycerols within the adipose tissue, a process called reesterification. The other FAs are transported to the other tissues and taken up by skeletal muscle during exercise. Glycerol is transported to the liver, where it serves as a gluconeogenic substrate to form new glucose.
Besides the FAs in plasma, two other sources of FAs for oxidation in skeletal muscle are available. Circulating triacylglycerols (for example in a very low-density lipoprotein [VLDL]) can temporarily bind to lipoprotein lipase (LPL), which splits off FAs that can then be taken up by the muscle. A source of fat exists inside the muscle in the form of intramuscular triacylglycerol. These triacylglycerols are split by a hormone-sensitive lipase (HSL), and FAs are transported into the mitochondria for oxidation in the same way that FAs from plasma and plasma triacylglycerol are utilized.