There is a general consensus that excessive fat consumption is a contributing factor in obesity, cancer, and heart disease. The prevailing medical opinion is that Americans eat too many fatty foods. Excessive fat consumption has been singled out as the number one dietary problem in the United States; average fat consumption is 130 pounds a year per person, which includes animal fat, vegetable oil, shortening, margarine, and partially hydrogenated vegetable oils. This consumption is about twice as much fat and oil as is considered healthy by some experts. The dietary guidelines for Americans (U.S.) recommend cutting back on fat by at least 25 percent, so that total fat accounts for no more than 30 percent of daily calories for adults.
Fat contributes to obesity in part because it is easier to gain weight from eating excess fat than it is from eating excess carbohydrate. The body’s metabolism is not efficient in converting sugar to fat; about a quarter of the calories in sugar are lost in the conversion. On the other hand, only 3 percent of the calories in consumed fat is expended in converting dietary fat to body fat. A high-fat diet promotes water loss and electrolyte imbalance and may increase uric acid levels and increase the risk of gout. It also increases the risk of kidney dysfunction.
Cancer
A high-fat intake is one of the strongest risk factors for cancer, after cigarette smoking. For example, lung cancer risk increases with diets high in saturated fat. High-fat diets decrease the ability of the immune system to destroy cancer cells, and eating less animal fat and vegetable oil lowers the risk of colon, prostate, and, possibly, breast cancer.
Overconsumption of fat increases the risk of heart disease in American populations. A diet with too much animal fat tends to raise blood cholesterol. On the other hand, polyunsaturated vegetable oils help lower blood cholesterol levels, believed to decrease the risk of heart disease, fish and fish oil also seem to protect against heart disease. A special ingredient of fish oil, omega-3 fatty acids, balances the immune system, and decreases inflammation. Fish and fish oils slow down blood clotting, lower serum fat, and perhaps cholesterol levels, and may reduce the risk of heart attacks. People who are generally angry or anxious have higher cholesterol levels; they degrade fat more slowly than others. Consequently, slow fat breakdown may be one of the risk factors in heart attacks.
A very-low-fat diet, with 10 percent of calories from fat, was incorporated into a program to reduce the risks in people with heart disease. The program included exercise, stress reduction, counseling, and support groups. Men who changed their lifestyle managed to reverse clogged arteries and to keep off lost weight for four to eight years.
Recommendations to Reduce Fat Calories
• Eating less fat by eating fewer servings and smaller portions. Being realistic about expectations rather than totally eliminating favorite fatty foods. Dairy products like butter and sour cream and plant-derived fat, like coconut oil, palm and palm kernel oil, shortening, margarine, and chocolate, are sources of saturated fat. Vegetable oils such as safflower oil, corn oil, soybean oil, and mayonnaise represent unsaturated fat. Substituting low-calorie margarine and low-calorie mayonnaise. Using spices, vinegar, or lemon juice rather than oily salad dressing.
• Reducing consumption of fat in meat by trimming off visible fat or by using only lean meat (“select” or good quality beef). Eating fewer hot dogs, hamburgers, and sausage. Draining fat after browning meat. Removing skin from chicken and turkey. Broiling, baking, poaching, or steaming food rather than eating fried foods.
• Chilling soups and discarding coagulated fat. Cooking vegetables in water and herbs instead of sauteing them in butter. Eating tuna packed in water, not oil. Baking fish with lemon juice instead of butter.
• Avoid pastry and rich desserts like ice cream.
• Using skim milk, nonfat yogurt, and lowfat cottage cheese rather than products derived from whole milk. Avoiding adding sour cream and cheese toppings to baked potatoes.
(See also atherosclerosis; body mass index; dieting; eating patterns.)
Fat fold test (skin fold test)
A convenient method of estimating body FAT. This test relies on a measurement of the width of a fold of skin on the back of the upper arm or other part of the body. Skin fold measurements, together with measurements of waist and hip circumference, have been used to estimate bone growth and changes in muscle mass during weight loss or weight gain. A caliper that applies a fixed pressure is used to measure skin fold thickness. A fat fold of more than an inch wide reflects obesity. The fat at the back of the arm or from the upper back is roughly proportional to total body fat. When fat is gained, or lost, the fat fold increases and decreases proportionately. The test requires an experienced assessor for reliable results.
The distribution of fat is important in considering the risk of cardiovascular disease because abdominal fat, not hip fat, is correlated with an increased risk. Abdominal fat seems to be more easily metabolized by the liver and converted to low-density lipoprotein (LDL), the undesirable form of cholesterol. (See also body mass index; height/weight tables; lean body mass.)