Your body needs some dietary fats, especially the healthy unsaturated fats that you can't make yourself, including omega-3 fatty acids. But dangers are associated with eating too much total fat, saturated fat and trans fats. You can protect your health and lower the risk of gaining weight or developing cardiovascular disease, type 2 diabetes and other chronic diseases by carefully choosing the amount and type of fat in your daily diet.
Weight Gain From Eating Too Much Fat
Eating too much of any food -- including fat -- leads to weight gain, but fat may be riskier than carbs and proteins because it contains more calories. One gram of fat has 9 calories, compared to 4 calories per gram of dietary carbs and fat. Even if your diet contains fewer fats than carbs or protein, the fats could contribute a large percentage of the total calories.
Besides the high calorie count, fat may contribute to weight gain because it doesn’t make you feel as full as other macronutrients. Fats also burn fewer calories during digestion, barely affecting energy expenditure. By comparison, carbs increase calories burned by 5 to 10 percent, and proteins boost energy used by 15 to 30 percent, reported Nutrition and Metabolism in November 2014.
Saturated fats are more likely to add pounds than unsaturated fats, reported the European Journal of Nutrition in April 2014. Finally, the overall composition of macronutrients in your diet makes a difference. Evidence consistently shows that lower fat intake leads to small but significant weight loss.
Danger of Cardiovascular Disease From Dietary Fat
When oil is hydrogenated, it changes from a healthy liquid oil to an unhealthy trans fat. Trans fats boost blood levels of bad cholesterol, or low-density lipoprotein, while lowering the amount of good cholesterol, or high-density lipoprotein. For every 2 percent of your calories you get from trans fats -- or about 4 grams of trans fats based on consuming 2,000 calories -- your risk of heart disease rises by 23 percent, according to Harvard Medical School. Trans fats are being eliminated from many products, but look for them in fried foods, margarine, shortening and commercially prepared baked goods.
Most types of saturated fat increase the amount of harmful cholesterol, which collects on artery walls. Over time, it builds up, blocks blood flow and causes a stroke or heart attack. The risk of coronary heart disease goes down when saturated fats are replaced by unsaturated fats. Saturated fats are solid at room temperature, so you’ll find them in animal fat, whole milk and products made from whole milk, such as cheese and butter.
Cholesterol is commonly considered an unhealthy fat, but for most people, dietary cholesterol has a small impact on blood levels of cholesterol. If you have high cholesterol, heart disease or diabetes, talk to your doctor about how much cholesterol is safe for you. However, if you're otherwise healthy, you don't typically need to worry about your cholesterol intake.
Excessive Fat Intake and Chronic Disease
The U.S. Food and Drug Administration states that total fat intake alone is associated with an increased risk of cancer, but studies so far haven’t discovered how a high-fat diet may cause cancer or whether it’s more likely to result in one type of cancer over another. Dietary fat intake can also contribute to chronic diseases if it leads to weight gain. Being overweight increases the risk for type 2 diabetes, osteoarthritis, coronary heart disease and gallbladder disease. Excess weight may also be associated with some types of cancer.
While the FDA doesn’t finger specific fats, saturated fats are known to trigger inflammation in fat cells and chronic inflammation contributes to diabetes, arthritis and heart disease. By comparison, omega-3 fatty acids help prevent chronic disease by reducing inflammation. The omega-6 fatty acids have a dual role. Omega-6, or linoleic acid, generally has an inflammatory effect, but it can also be converted into arachidonic acid, which has a pro- and anti-inflammatory influence.
In lab rats, excessive intake of linoleic acid promoted inflammation, reported the Journal of Nutritional Biochemistry in December 2015. On the other hand, a review of studies published in Circulation in 2014 reported that people who consumed more linoleic had a lower chance of coronary heart disease. Until more conclusive evidence is produced, it’s best to follow the recommended daily intakes established by the Institute of Medicine.
Recommended Fat Intake
Twenty to 35 percent of your total daily calories should come from dietary fats, according to the Institute of Medicine. Based on consuming 2,000 calories daily, that translates into 44 grams to 78 grams of fats. Women should get 1.1 gram of total omega-3 fatty acids and 12 grams of omega-6 fatty acids daily. Men need 1.6 grams of omega-3 and 17 grams of omega-6 each day. Healthy unsaturated fats are primarily found in nuts, seeds and vegetable oils. Sources of omega-3 include walnuts, flaxseeds, canola oil, soybean oil and fish, such as salmon, trout and tuna. Some good choices for omega-6 include sunflower seeds, pecans, safflower oil, brazil nuts and corn oil.
The American Heart Association recommends limiting saturated fats to less than 7 percent of daily calories, or a maximum of 16 grams based on getting 2,000 calories daily. Try to completely avoid trans fats, but don’t consume more than 1 percent of your total calories in trans fats. That means no more than 2 grams for a 2,000 calorie-a-day diet. If you need to lower your cholesterol, reduce saturated fat to 5 percent or less of total calories.
- Nutrition and Metabolism: A High-Protein Diet for Reducing Body Fat: Mechanisms and Possible Caveats
- European Journal of Nutrition: Effect of Dietary Fatty Acid Composition on Substrate Utilization and Body Weight Maintenance in Humans
- British Medical Journal: Effect of Reducing Total Fat Intake on Body Weight: Systematic Review and Meta-Analysis of Randomised Controlled Trials and Cohort Studies
- Harvard Medical School: The Truth About Fats: The Good, the Bad and the In-Between
- Harvard School of Public Health: Eggs and Heart Disease
- U.S. Food and Drug Administration: Specific Requirements for Health Claims: Dietary Lipids and Cancer
- Nutrients: The Relationship Between Dietary Fatty Acids and Inflammatory Genes on the Obese Phenotype and Serum Lipids
- Oregon State University: Linus Pauling Institute: Essential Fatty Acids
- Journal of Nutritional Biochemistry: Excessive Dietary Linoleic Acid Induces Proinflammatory Markers in Rats
- Circulation: Dietary Linoleic Acid and Risk of Coronary Heart Disease: A Systematic Review and Meta-Analysis of Prospective Cohort Studies