The Differences Between Good Fats and Bad Fats

You've probably heard that there are good fats and bad fats. But do you know exactly what the differences are? We'll tell you about them in detail.

Written and verified by el nutricionista Saúl Sánchez.

Last update: 19 June, 2023

Most of the fats are nutrients that are beneficial to health. They fulfill really important functions in the body, modulating many hormonal processes or vital physiological reactions. If good fats aren’t consumed in sufficient quantities, diseases can be experienced in the medium term.

Now, not all fats are positive. There’s a small group of them whose consumption can have a negative impact on health, generating chronic problems. For this reason, their presence in the diet must be limited. It’s not necessary to suppress them completely but to reduce their intake.

What are good fats?

Good fats are all those found in fresh food prior to the cooking process. As for their chemical structure, the number of bonds they have inside is indifferent. In this regard, it doesn’t matter whether they’re saturated or unsaturated, but rather the arrangement of their molecules in space. It’s essential that they have a cis conformation.

For many years, the consumption of saturated lipids was demonized. However, it’s currently known that these are necessary and that they’re beneficial for the body. This is evidenced by a study published in the journal Critical Reviews in Food Science and Nutrition. However, you have to consume them in their proper measure and under proper cooking methods.

It shouldn’t be forgotten that fats are nutrients with high energy density. This means that they provide a lot of calories per gram. If ingested in excessive amounts, weight gain can be experienced from an energy imbalance. This condition is considered harmful to health, regardless of whether the nutrients that have been consumed are of good quality.

Likewise, within the “good fats,” a certain proportion must be respected. An example is the ratio between omega-3 and omega-6 fatty acids. Ideally, the intake of both elements should be more or less even, as they have antagonistic functions on inflammatory mechanisms.

If the balance becomes unbalanced, you may experience health problems in the medium term. In fact, the intake of omega-6 acids is often over-promoted, which is seen as harmful. This is indicated by research published in The Journal of Nutrition . This isn’t to say that omega-6 lipids are bad, not at all, just that the ratio is important.

Where are good fats found?

Good fats can be found in many different fresh foods. Both meat and fish provide these types of nutrients, as do eggs and dairy. Regarding the latter, the consumption of skimmed versions has been recommended for many years, something that current literature advises against.

It must be taken into account that many vitamins dissolve in the fat of food. If it’s removed from its composition, essential micronutrients will be lost, such as vitamins A, D, or E. All of them are necessary to ensure a correct state of health. They have many functions within the body. In fact, some of them are characterized by their antioxidant power.

Good fats are also concentrated in plant-based foods. Oils are a great alternative. Of course, it’s important to consume the less refined varieties. As processing increases, the quality of the food decreases, becoming contaminated with waste or including fatty acids that have been adulterated through physicochemical processes.

Likewise, oily fruits such as avocado, nuts, and seeds can be included in the diet to complete the supply of these nutrients. All the elements stand out for their nutritional density and for their energy value. They have in their interior essential micronutrients such as vitamins and minerals, which are necessary to ensure good health.

In fact, both foods of animal origin and others of plant origin that stand out for their healthy fat content should appear on a daily basis. In the opposite case, deficits could be experienced that negatively condition the functioning of the organism in the medium and long term.

What are bad fats?

Bad fats are known as those present in ultra-processed foods or in products that have been subjected to aggressive thermal processes. Heat generates a change in the spatial arrangement of the fatty acid molecules, which causes them to take on a trans conformation. These elements have been shown to be capable of increasing the risk of becoming ill, according to a study published in Cardiology.

These nutrients, regardless of the double bonds they contain inside, have inflammatory properties. Its presence in the regular diet alters the normal functioning of the body. According to research published in the journal Diabetes & Metabolic Syndrome, their consumption is associated with the development of chronic diseases such as diabetes, cancer, and cardiovascular diseases.

The problem is that trans lipids aren’t reflected in nutritional labels. Producers of processed foods aren’t required to declare them, so they go unnoticed by many people. In addition, they’re a class of substances that can be formed in homemade preparations, when pieces of meat or fish are fried.

It must be clear that subjecting foods with lipids inside to aggressive thermal processes causes a change in the spatial configuration of a good part of them. This is where trans fatty acids are produced. However, this mechanism doesn’t always develop with the same ease. For example, saturated fats are more sensitive to this transformation.

As a general rule, it’s recommended to avoid fried foods, batters, burned foods, and those baked at high temperatures. However, if these cooking methods are to be applied, it’s important to ensure that the oils used and the foods chosen have unsaturated lipids inside them. The more double bonds they have in their chemical structure, the lower the transformation ratio.

Where are bad fats found?

As we’ve discussed, bad fats are found mainly in ultra-processed foods. By this, we don’t mean any product handled industrially. For example, most preserves are considered safe and healthy. The harmful group basically includes prepared meals, pastries, sweets, fast food, etc…

When planning a healthy diet, it’s important to greatly limit the presence of these foods. The idea is also not to reduce your trans fat intake to zero, as this is impossible. Even breast milk has a small proportion of these nutrients. But it’s important that their consumption be limited to avoid promoting inflammatory mechanisms.

These types of nutrients not only have a high energy intake but can also generate inefficiencies at the metabolic level. One of them is insulin resistance. When this dysfunction is promoted, it becomes easier for the person to gain weight easily, reaching states of obesity. It’s good to remember that this condition has been shown to be really unhealthy.

When it comes to homemade meals, it’s essential to watch the cooking methods so that bad fats aren’t formed. Those recommended by experts are skillets, steam, baking at moderate temperatures, and cooking with water. With these mechanisms, correct food hygiene, good palatability of the products, and the low transformation of fatty acids are ensured.

When adding some type of vegetable fat during the production process, those products with unsaturated lipids must always be prioritized. Vegetable oils like olive and avocado are good options. However, seed and coconut oils should be avoided. These are optimal for eating raw, but not for cooking.

Just the same, there’s no great problem with their raw consumption. For example, there’s evidence that coconut fats are beneficial for cardiovascular health. They can be included in the diet without problem, but ensuring that these lipids are cis-type.

Likewise, butter shouldn’t be used in culinary preparations. This element is very sensitive to temperature rises, undergoing transformations in the fatty acids that it houses inside. Different is the case of ghee, which despite being a derivative of butter itself, has a superior resistance to heat.

What’s the maximum amount of fat that can be included in the diet?

It’s clear that consuming little fat is problematic. This can lead to a deficit of fat-soluble vitamins that worsens health. In addition, the fatty acids themselves modulate inflammatory and homeostatic processes, apart from participating in hormonal reactions.

However, an excess of lipids in the diet can also be counterproductive, even if the fatty acids ingested are of the trans type. The truth is that there’s no maximum number of grams of fat that should be included in the diet. Here, you have to be guided by the total energy intake.

One of the pillars of a healthy diet is balance from the caloric point of view. This principle ensures the maintenance of body weight, something that’s considered essential in cases where there’s no previous excess weight. For this reason, it’s essential to adjust the intake to the calories expended throughout the day.

From here, it’s important to calculate the protein needs. These normally account for 20% of the total calories. Perhaps more in some contexts. The optimal thing is to consume more than 0.8 grams of protein per kilo of weight per day in the case of sedentary people, reaching almost triple the value in athletes.

The remaining calories have to be divided between the good fats and the carbohydrates. As a general rule, and in a scenario of low physical activity, fat consumption has a greater role. You can reach 60 grams of these nutrients per day in sedentary people without major problems. Even more so in the context of ketogenic diets.

Now, as the rate of physical exercise increases, carbohydrates will gain prominence. Especially when the type of work performed is power or maximum strength. In this case, sugars take on special importance as they’re the main energy substrate. Just the same, don’t neglect fat intake.

What are the symptoms of a good fat deficiency?

On some occasions, the minimum requirements for good fats may not be met. This usually generates symptoms in the medium term, among which fatigue, dermatological problems, altered bowel habits, and the promotion of inflammatory states stand out.

It must be taken into account that if there are preexisting diseases of a complex nature, an inefficient supply of unsaturated lipids can magnify the symptoms. An example would be irritable bowel syndrome, where a regular consumption of omega-3 is necessary to maintain an inflammatory balance and reduce episodes of crisis or pain.

The same is the case with rheumatoid problems, where insufficient fat intake can lead to more pain. In these cases, a significant improvement is experienced when a dietary adjustment is made to ensure optimal nutrient consumption.

Good fats and bad fats differ in the arrangement of their molecules

As you’ve seen, the difference between good fats and bad fats is small. The key is in the spatial arrangement of the fatty acid molecules that compose them. Thermal processes can cause alterations that change the healthiness of these nutrients, as well as their effects on the body.

To ensure optimal consumption of good fats, the presence of fresh food in the daily diet is recommended. Oily fish and meats make a good contribution to them. Also, products of plant origin such as oils, nuts, avocados, and seeds. The key is to increase the variety of foods consumed to avoid deficits.