Low-Fat Diet

Introduction

High-fat diets are associated with increased risk of several serious medical conditions including obesity, cancer, and heart disease. Consequently, current public health recommendations emphasize the importance of reducing total fat intake to no more than 30% of total calories, or 60 grams of fat per day in an 1800 calorie diet. Tips for reducing fat intake include lowering intake of whole fat dairy products, red meats, and high-fat condiments. While most people can improve their health by reducing the total amount of fat in their diet, the consumption of fat by children under the age of two should not be restricted. In addition, adults reducing their total fat intake should still be careful to include adequate amount of specific, essential fats, particularly the omega 3 fatty acids.

History

During the past 20 years, the amount and type of dietary fat that should be present in a healthy diet has been the source of tremendous controversy. Although fat is often portrayed as a dietary villain by the popular media, fat participates in five essential physiological functions.

  1. Fat serves as a source of energy for the body by supplying 9 calories per gram (compared to 4 calories per gram from carbohydrates and protein).
  2. Stored fat helps maintain body temperature and protects vital organs from injury.
  3. Dietary fat aids in the absorption and transport of the fat-soluble vitamins (A, D, E and K) and other fat-soluble nutrients.
  4. Fat improves the taste and mouth feel of food and provides a sense of satiety that helps us moderate how much food we eat at one time.
  5. Dietary fat provides two essential fatty acids (the omega 3 fat, alpha-linolenic acid, and the omega 6 fat, linoleic acid) both of which are necessary for a wide variety of important physiological processes.

Eating too much of the wrong kinds of fat, however, can increase our chances of becoming obese, or developing heart disease or cancer. As a result, various health and nutrition organizations, including the US Surgeon General, US Department of Health and Human Services, and the US Department of Agriculture favor a “low-fat” diet and have issued dietary recommendations that include reducing intake of total and saturated fat. In general, these guidelines suggest that for persons older than two years, total fat intake should not exceed more than 30% of total caloric intake and that saturated fat should account for no more than 10% of daily caloric intake. For total fat, this guideline means no more than 60 grams of fat per day on an 1800 calorie diet, and within that total fat, no more than 20 grams of saturated fat.

Popularity

With the growing recognition of the dangers of eating too much fat, and the plethora of "low-fat" and "fat-free" foods on the supermarket shelves, you would think that everyone in the United States is eating a low-fat diet. Unfortunately, recent statistics suggest that the opposite is true. According to the USDA’s Continuing Survey of Food Intakes by Individuals, actual fat consumption has increased slightly over the past few decades, from approximately 81 grams per day in the late 1970s to about 83 grams per day in the early 1990s. In addition, results from the Third Report on Nutrition Monitoring in the United States indicate that a majority of the United States population fails to meet current recommendations for dietary fat consumption. In fact, only 21% and 25% of males and females 20 years old and older consume less than or equal to 30% of calories from fat. Children and adolescents are doing even worse than their parents at meeting current recommendations. Only about 18% of boys and girls aged 6 to 11 consume less than or equal to 30% of calories from fat, and only 14% and 18% of boys and girls, respectively, aged 12 to 19 meet current dietary recommendations for fat intake. The reason? Consumption of the major sources of dietary fat in the American diet, which include red meat, poultry, and dairy products (cheese, half and half, and ice cream) has not decreased, and consumption of high-fat snack foods, especially among children, is on the rise. All of this, despite the widespread availability of "low-fat" and "fat-free" food choices.

Principles

In general, any diet, regardless of the foods eaten, can be considered "low-fat" if it includes no more than 30% of total calories as fat, which is 60 grams of fat per day in an 1800 calorie diet. Consequently, there is no prescribed "low-fat" diet that mandates the exact foods that must be eaten. Some people choose to cut back on the amount of red meat they eat, while others avoid high-fat desserts, snack foods, condiments, or nuts. It is important to remember, however, that not every low-fat diet is necessarily a "healthy" diet. In fact, many people following a low-fat diet substitute foods that contain fat with "fat-free" processed foods that contain large amounts of sugar, salt, additives, and preservatives. So, what exactly can you do to develop a healthy, low-fat diet? Here are some tips for reducing your fat intake and promoting good health:

  • First and foremost, avoid all foods containing partially hydrogenated oils, which are also called trans-fats. A growing body of research indicates that these fats are harmful to your health.
  • Sauté vegetables and meat in vegetable broth instead of butter or vegetable oil.
  • Read food labels carefully, paying close attention to the serving size and number of servings per package. Some labels are intentionally misleading, in that the serving size listed is much smaller than the amount of the food that is usually consumed, which means you might end up eating more fat than you think. (For more information on what those labels really mean, see "Label Terminology" immediately below.)
  • Decrease your consumption of meat. Substitute a bean dish or a "meat" made from soy for red meat dish as your main course as often as possible.
  • When you do eat meat, choose leaner cuts of beef and trim any visible fat before cooking. To keep poultry moist, do not remove the skin before cooking, but take the skin off before eating. Or better yet, remove the skin, and braise or sauté your chicken in vegetable broth.
  • Limit your consumption of whole-fat dairy products or substitute low or non-fat alternatives for them.
  • Increase the amount of fruits, vegetables and whole grain foods you eat. You'll have less room and less desire for high-fat snacks.
  • Decrease your use of high-fat condiments, such as butter and mayonnaise. Order your salad dressing on the side, then dip your fork in the dressing before each bite. You'll be surprised at how little dressing you actually need to flavor your salad, and the dressing that remains on the side will not remain on your stomach, thighs or hips!
Label Terminology

When you're trying to lower your total fat intake, knowing the true meaning of those fat-related phrases on packaged foods will come in handy. Here's the low-down on label terminology:

  • Fat Free: contains less than 0.5 grams of fat per serving
  • Saturated Fat Free: contains less than 0.5 grams per serving and the level
  • of trans fatty acids does not exceed 1% of total fat
  • Low Fat: contains 3 grams or less per serving or per 50 grams of food (if the serving size is less than 30 grams or 2 tablespoons)
  • Low Saturated Fat: contains 1 gram or less per serving and not more than 15% of calories from saturated fatty acids
  • Reduced or Less Fat: contains at least 25% less per serving than reference food
  • Reduced or Less Saturated Fat: contains at least 25% less fat per serving than its full-fat counterpart. For example, milk that is labeled as "reduced fat" must contain at least 25% less fat than whole milk.

Fat Chemistry

A final bit of information you may find helpful when trying to eat low-fat is a little insight into fat chemistry. You'll find many of the terms below on the ingredient lists of packaged foods. Knowing more about the different types of fat can help you improve the quality of the fats you consume, as well as help you lower your total fat intake.

Fats are composed of chains of carbon atoms, to which hydrogen and oxygen atoms are attached. Dietary fats are divided into different categories depending on the arrangement of hydrogen atoms in the carbon chain and the shape of the fat molecule. The four main categories of dietary fats are saturated fats, monounsaturated fats, polyunsaturated fats, and hydrogenated fats. Although foods almost always contain a mixture of different types of fats, foods that contain fat are typically classified by the type of fat that is most prevalent in the food. Here are some short profiles of these different types of fats:

  • Saturated fats: Saturated fats contain large amounts of saturated fatty acids. Saturated fatty acids are so-named because they are "saturated" with hydrogen, meaning they have only single bonds between the carbon atoms in the chain, leaving no room in their chemical structure for additional hydrogen atoms. Saturated fats are typically solid at room temperature. Sources of saturated fat include butter, coconut and palm oil, red meat, poultry, and lard. High dietary intake of saturated fat is associated with elevated cholesterol levels and an increased risk for heart disease.
  • Monounsaturated fats: Monounsaturated fats contain large amounts of monounsaturated fatty acids. Monounsaturated fatty acids are so-named because, due to the presence of one double chemical bond in the carbon chain, the fatty acid is not "saturated" with hydrogen. Monounsaturated fats are typically liquid at room temperature, but solidify when refrigerated. Sources of monounsaturated fat include olive oil, canola oil, peanut oil, and avocados. Historically, monounsaturated fats, and specifically olive oil, were the most prevalent fats in the diets of people living in the Mediterranean and may be partly responsible for the low rates of many degenerative diseases including cancer, diabetes, and heart disease seen in this region.
  • Polyunsaturated fats: Polyunsaturated fats contain large amounts of polyunsaturated fatty acids. Polyunsaturated fatty acids are so-named because due to the presence of two or more double chemical bonds, there are places along the carbon chain where the fatty acid is not "saturated" with hydrogen. Polyunsaturated fats are liquid at room temperature and remain in liquid form when refrigerated or frozen. The two essential fatty acids, linoleic acid and alpha-linolenic acid, are polyunsaturated fatty acids. Each of these two essential fatty acids is highly unique and important in health. Linoleic acid is the basic building block for a group fats called the omega 6 fatty acids. Linolenic acid is the basic building block for another group of fats called the omega 3 fatty acids. In the U.S., intake of polyunsaturated fats is highly unbalanced. Many individuals in the U.S. consume excess polyunsaturated fat, but too little of the two essential building blocks (linoleic and linolenic acid). Even worse, virtually all individuals in the U.S. - even those who do consume enough of the omega 6 building block (linoleic acid) - do not consume nearly enough of the omega 3 building block (linolenic acid). The bottom line? When you go low-fat, be especially careful to maintain adqeuate intake of one type of polyunsaturated fats - the omega 3 fatty acids. Best food sources of omega 3s include flax seeds, hemp seeds, pumpkin seeds, sunflower seeds, sesame seeds, soybeans, and wild-caught fatty fish such as salmon. High dietary intake of omega 3 fats is associated with a decreased risk for heart disease, and may be beneficial in the treatment of a variety of health conditions including the autoimmune diseases (for example, lupus and rheumatoid arthritis).
  • Hydrogenated fats: Hydrogenated fats, also known as trans fats, are produced through a chemical process called hydrogenation. Hydrogenation adds hydrogen to various places in the fatty acid chain, thereby converting the unsaturated bonds in the oil into saturated bonds, creating a solid, spreadable fat with increased shelf life. When the hydrogenation process is not complete (meaning that not all unsaturated bonds are converted to saturated bonds), the structure of the fatty acids is transformed from the fats' natural "cis" configuration to a "trans" configuration. Trans fats are associated with an increased risk for heart disease. Partially hydrogenated fats hide out in a wide variety of processsed foods, so it's a good idea to always check labels. Primary sources of these fats include margarine, shortening, and many processed foods (for example, potato chips, tortilla chips, non-dairy creamers, breads, muffins, cookies, and candy).

Research

A significant amount of population-based research indicates that consumption of a diet high in total and saturated fat is associated with an increased risk for several medical conditions, such as obesity, heart disease, high blood pressure, insulin resistance, gallbladder disease, and certain cancers (for example, breast, colon, and prostate cancers).

On the other hand, critics of the "low-fat" craze argue that low-fat, high carbohydrate diets actually increase triglyceride levels and lower levels of HDL, the protective form of cholesterol. Research indicates that high triglyceride levels and low HDL levels are associated with an increased risk for heart disease.

Foods Emphasized

A healthy low-fat diet emphasizes the consumption of whole grains, beans, fruits, and vegetables, as well as small amounts of healthy sources of fat including raw nuts, raw seeds, vegetable oils (particulary monounsaturated oils like olive oil, and oils rich in omega 3 fats such as flaxseed oil and soybean oil), and cold water fish including salmon, herring, and mackerel.

Foods Avoided

Low-fat diets often exclude or limit red meats, whole fat dairy products (butter, milk, yogurt, heavy cream and ice cream), mayonnaise, margarine, and salad dressings. Extremely low-fat diets, such as the Dean Ornish Diet and the Pritikin diet, eliminate nearly all animal products and added vegetable oils.

Nutrient Excesses/
Deficiencies

Low-fat diets often contain a large amount of simple carbohydrates and refined sweeteners, especially when "low-fat" and "fat-free" processed foods are eaten. According to the USDA’s 1995 Continuing Survey of Food Intakes by Individuals, the intake of sugar and other refined sweeteners increased from about 55 kg (120 lb) per person per year in 1970 to 68 kg (150 lb) per person per year in 1995. In addition, extremely low-fat diets may contain insufficient quantities of the omega 3 and omega 6 essential fatty acids.

Who Benefits

Fat is the most calorie-dense macronutrient (fat contains 9 calories per gram compared to 4 calories per gram for protein and carbohydrate), so foods containing fat are usually high in calories. If you are trying to lose weight by counting calories, reducing your consumption of high-fat foods can be beneficial. Also, if you have heart disease or cancer, or have a family history of either disease, your health may be improved by eating a diet that is low in total and saturated fat.

Who is Harmed

Following a low-fat diet (or a diet that contains fewer than 30% of calories as fat) is unlikely to cause any harm to healthy adults eating a varied and well-balanced diet, assuming they consume an adequate amount of essential fatty acids, especially the omega 3 fats. However, children require extra fat to maintain normal growth and development. As a result, the consumption of dietary fat by infants and children less than two years old should not be restricted.

Menu Ideas

Try a few of our favorite low-fat recipes . . .

Resources

For more information about how to cut the fat out of your diet, check out the following web pages:

References

  • American Dietetic Association. Fat replacers - ADA position. Journal of the American Dietetic Association 1998; 98: 463-68.
  • Cerrato PL. Low-fat diet, lower risk of colorectal cancer. RN 1991 Sep;54(9):71-3.
  • Cheung ST. Possible dangers in a low fat diet: some evidence reviewed. Nutr Health 2000;14(4):271-80.
  • Corle DK, Sharbaugh C, Mateski DJ, et al. Self-rated quality of life measures: effect of change to a low-fat, high-fiber, fruit and vegetable enriched diet. Ann Behav Med 2001 Summer;23(3):198-207.
  • Higashi K, Shige H, Ito T, et al. Effect of a low-fat diet enriched with oleic acid on postprandial lipemia in patients with type 2 diabetes mellitus. Lipids 2001 Jan;36(1):1-6.
  • Lytle LA. In defense of a low-fat diet for healthy children. J Am Diet Assoc 2000 Jan;100(1):39-41.
  • Mahan K, Escott-Stump S. Krause's Food, Nutrition, and Diet Therapy. WB Saunders Company; Philadelphia, 1996.
  • McManus K, Antinoro L, Sacks F. A randomized controlled trial of a moderate-fat, low-energy diet compared with a low fat, low-energy diet for weight loss in overweight adults. Int J Obes Relat Metab Disord 2001 Oct;25(10):1503-11.
  • Rasmussen KM, Wallace MH, Gournis E. A low-fat diet but not food restriction improves lactational performance in obese rats. Adv Exp Med Biol 2001;501:101-6.
  • Walker KZ, O'Dea K. Is a low fat diet the optimal way to cut energy intake over the long- term in overweight people. Nutr Metab Cardiovasc Dis 2001 Aug;11(4):244-8.

This page was updated on: 2001-05-30 04:15:39
© 2002 The George Mateljan Foundation