Fat - A Necessary Part of Any Human Diet
Eating fat is a necessary part of any human diet. Fats serve many essential functions, from providing energy to helping absorb vitamins to keeping warm. Fats come in different forms though, some noticeably healthier than others. The unhealthy forms of fat are the ones that are most closely connected to the global epidemics of obesity and obesity related conditions, such as metabolic syndrome, type 2 diabetes and cardiovascular disease(CVD).
Being a macronutrient, fat is an important source of energy, and is necessary for proper organ function and insulation within the body.
Fats provide the body with energy, more than twice as many calories per gram (or ounce) as the other macronutrients, carbohydrates and proteins. They also help the body absorb “fat-soluble” vitamins such as vitamins A, D, E and K. Omega 3 and Omega 6 fatty acids are also “essential” fats that come from food and serve to help maintain circulation and neurological balance, and decrease inflammation. So eliminating fat from a diet not only is not a realistic option, it is not a good idea.
Eating low-fat diets also are not a conscious objective for those looking to promote overall health. The first reason is that most low-fat diets replace both healthy and unhealthy fats with higher levels of refined carbohydrates, which themselves have shown a greater connection to obesity and type 2 diabetes than eating fat. The other reason to not strive for a low-fat diet is that healthy fats, which are described below, are a valuable source of nutrition and energy in a balanced diet.
Weight Gain is Not A Product of Dietary Fat Consumption
An important point to always remember is that weight gain principally occurs due to excess calories(energy), not excess dietary fat, and most foods and beverages contain calories, in varying degrees. If more calories enter the body than are used for energy, they can be stored as fat, in the tissues, cells and blood (clinically the metabolic conversion of glucose[sugar] to fat is called “lipogenesis”). This can happen due to over-consumption (eating and drinking too many overall calories), or by eating too many foods that are digested quickly, such as with refined carbohydrates and sugary beverages. In the later case of “fast” foods (meaning quickly digested foods, not simply the famed unhealthy restaurants), the body is flooded with energy in the form of glucose that is too much to be used as energy in the moment (especially for inactive individuals), so this excess energy is eventually stored as fat and can also lead to prediabetic conditions such as insulin resistance. The main point is that one does not lose or control weight by cutting out fat, they lose it by eating balanced diets without too many calories and eating foods where energy is digested and absorbed gradually instead of in a rush. Whole grains, fruits, vegetables, beans and legumes, nuts and seeds, and the moderate consumption of unprocessed lean animal protein such as fish and poultry, as well as possibly some dairy, is the recommended approach for maintaining a healthy weight through diet.
The next major point to address is that fats come in different forms, and vary in their overall healthfulness and utility to the body. Unprocessed foods contain both unsaturated fats and saturated fats, while certain processed foods, especially hydrogenated vegetable oils (like margarine) contain trans fatty acids. Unsaturated fats are the most beneficial, saturated fats can be healthy when eaten in moderation, and trans fats are entirely unhealthy.
Unsaturated fats are liquid at room temperature, and themselves are divided into monounsaturated and polyunsaturated fats. They come principally from plants and oils derived from plants, though certain fish like salmon and tuna are also valuable sources of unsaturated fats (omega 3). Vegetable oils such as olive, peanut and sunflower, as well as nuts like walnuts and almonds and fruits such as avocados are examples of particularly good sources of unsaturated fats.
Eating unsaturated fats is a staple of famously healthful traditional diets, such as the Mediterranean diet. Unsaturated fats help with lowering LDL cholesterol levels, reducing inflammation, regulating blood glucose levels while helping to prevent type 2 diabetes, and promoting heart and overall body health.
Saturated fats are typically found in large amounts in animal products, such as meat and dairy. Butter is high in saturated fat, as is most cheese, milk, ice cream, red meat and processed meats like sausage, bacon and deli meats. The plant oils, coconut and palm, are also high in saturated fats. Palm oil itself is particularly abundant and destructive to human health and the environment in developing countries, and as a component in cheap consumer products and processed foods around the world. Heavy consumption of saturated fats has been connected to high levels of triglycerides in the blood that translates to high “bad” LDL cholesterol levels and high blood pressure. These are risk factors for heart and cardiovascular disease and type 2 diabetes. Triglycerides, also referred to as lipids, themselves are a fat found in the blood, and the most commonly connected to weight gain and obesity.
Trans fats come almost exclusively from industrially produced hydrogenated vegetable oils. Hydrogenation is the process of solidifying liquid vegetable oils through a chemical reaction of hydrogen gas and a catalyst at very high heat. These hydrogenated vegetable oils are “stable,” meaning they can be stored for long periods, and repeatedly reheated, for frying in fast food restaurants for example. They have been connected to a range of diseases, from heart disease and stroke, to certain cancers and type 2 diabetes. Trans fats both lower “good” HDL cholesterol and raise “bad” LDL cholesterol levels, induce inflammation, and have been connected to the prediabetes and type 2 diabetes risk factor, insulin resistance. While the vast majority of trans fats are consumed in industrial processed foods, there are small amounts of trans fats found naturally in dairy products and beef fat.
Positive trends have been occurring in most “developed” countries, such as the United States and in the European Union, to ban trans fats from almost all consumable products. With that said, cheap partially hydrogenated soy and palm oils are pervasive and contributing to growing health problems in many developing countries, where they are replacing more traditional and healthful cooking oils.
For a healthful and balanced diet, the recommendation here is to limit saturated fats and eliminate trans fats, replacing them instead with healthy unsaturated fats and other whole foods, such as whole grains. There is no benefit, and likely more harm done, by replacing fats in the diet with refined carbohydrates and processed “low-fat” foods that are typically high in added salt and sugar.
Learn More About Healthful Oils and Fats and Their Role in Diabetes Prevention and Management
Resources and Further Reading
A good summary of the types of fats and what kinds of foods contain them: https://www.hsph.harvard.edu/nutritionsource/types-of-fat/
A study about Unsaturated fats and diabetes prevention: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2654180/
The differences between Unsaturated and Saturated Fats: http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1000252
A study connecting trans fats and CHD incidence: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3024842/
A study about unsaturated fats in the Mediterranean diet and it’s overall health benefits: http://www.nejm.org/doi/full/10.1056/NEJMoa1200303
Solid resource out of Harvard for finding healthy fat foods: https://cdn1.sph.harvard.edu/wp-content/uploads/sites/30/2012/10/finding-foods-with-healthy-fats.jpg
More about triglycerides: https://www.webmd.com/cholesterol-management/lowering-triglyceride-levels#1
Studies showing positive trends of banning trans fats from products in the United States:
The most recent dietary recommendations for Americans from the USDA: https://health.gov/dietaryguidelines/2015/resources/2015-2020_Dietary_Guidelines.pdf
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