Scientific Weight Loss: A Re-evaluation of the Health Benefits and Guidelines for Choosing Dietary Fats

Making Friends with Dietary Fats Again

When it comes to obesity, dietary fat is perhaps the most memorable culprit. Since the 1980s, dietary fat has been burdened with a bad reputation, even demonized, causing people to avoid it at all costs. However, with the progress of time and science, dietary fat is gradually being scientifically vindicated. Beneficial dietary fats not only don't cause weight gain, but are also crucial for maintaining our health.

Besides providing delicious flavors, dietary fats offer numerous benefits. For women who care about their appearance, consuming good dietary fats is key to ensuring full, lustrous hair and hydrated, radiant skin.

At the same time, dietary fats support the functions of various important organs such as the brain and liver, and are also one of the raw materials for producing various hormones needed for body metabolism. Dietary fats also play an important role in regulating immunity, including helping the body absorb vitamins essential for life.

Vitamins are broadly divided into two categories: water-soluble vitamins and fat-soluble vitamins. Water-soluble vitamins are those that dissolve in water. However, because the human body cannot retain them for long periods, they need to be replenished frequently, such as B vitamins and vitamin C. Fat-soluble vitamins can only be dissolved and digested in a fatty environment. Fat-soluble vitamins include vitamins A, D, E, and K, which play important roles in helping us build muscles and bones, fight inflammation, and provide antioxidant benefits. People on long-term low-fat diets are prone to deficiencies in fat-soluble vitamins.

Good dietary fats not only help us accelerate metabolism and promote fat burning, but also help prevent diabetes, cancer, cardiovascular diseases, and neurological diseases such as depression. Therefore, successful weight loss is not about eliminating dietary fats, but about learning to choose good dietary fats.

Classification of Dietary Fats

To choose good dietary fats, you first need to understand what dietary fats are. Common cooking oils and most meat products are sources of dietary fats. After these foods are consumed, they are broken down into fatty acids. Based on their food source, fatty acids can be broadly divided into saturated fatty acids and unsaturated fatty acids. Generally, at room temperature, dietary fats that solidify easily are those high in saturated fatty acids; those that remain liquid are those high in unsaturated fatty acids.

The cooking oils we use in our daily lives are all mixtures of different fatty acids. For example, butter is mostly composed of saturated fatty acids, with unsaturated fatty acids making up only a small portion, so we usually refer to it as a saturated fat.

Because saturated fatty acids have no gaps in their molecular structure where they can bond with oxygen, they are in a saturated state, making them the most stable and least prone to oxidation, and having the highest smoke point. This type of dietary fat is very suitable for the high-temperature stir-frying methods favored by Chinese cuisine. Sources of saturated fatty acids include animal fats such as beef, pork, and lamb, as well as eggs and dairy products.

Unsaturated fatty acids have double bonds in their structure that saturated fatty acids lack. The more double bonds there are, the more easily they are oxidized by oxygen in the air, especially under high-temperature heating, which can easily produce harmful substances. Based on the number of double bonds, unsaturated fatty acids are divided into monounsaturated fatty acids (with only one double bond) and polyunsaturated fatty acids (with multiple double bonds).

Monounsaturated fatty acids, also called ω-9 fatty acids, are mainly found in olive oil, avocados, and nuts. This type of dietary fat is very beneficial for regulating cholesterol levels, insulin levels, and blood sugar levels in the human body.

Polyunsaturated fatty acids are essential fatty acids for the human body and are usually divided into two categories: ω-6 fatty acids and ω-3 fatty acids. The former mainly comes from vegetable oils such as soybean oil and corn oil; the latter is mostly found in cold-water fatty fish, such as salmon and tuna, and also in flaxseed and seaweed.

In addition to saturated and unsaturated fatty acids, there is another type of fatty acid containing one or more trans double bonds – the notorious trans fatty acid. Trans fatty acids are abundant in processed foods. They not only cause weight gain but also cause significant health damage, making them the type of dietary fat we should avoid consuming the most.