The Failure of Low-Fat Diets

Maybe you’ve been warned about the dangers of eating too much fat, or perhaps you’ve heard about the health benefits of certain types of fats. The truth is, dietary fats are not a one-size-fits-all subject. For years, fats were vilified, leading to a wave of low-fat diets in the late 20th century. Since then scientists have developed a much more nuanced understanding of the role of fats in our health. This guide takes you through the basic facts about dietary fats—why we need them, the different types, and how they affect your health.

The low-fat craze of the 1980s and 90s was based on the idea that cutting fat intake would reduce obesity and heart disease. However, it often backfired for a few key reasons:

• Fat Replacements: In many low-fat foods, fats are replaced with sugars and refined carbs, leading to weight gain and insulin resistance.

• Overeating: Without the satiety that fats provide, people consume more calories overall.

• Nutrient Deficiencies: Extreme low-fat diets deprive people of essential fatty acids and fat-soluble vitamins (A, D, E, and K).

• Misplaced Focus: The spotlight on fat distracted from other critical dietary and lifestyle factors.

We now know that avoiding any and all fats will not make us healthier. Fats are vital for good health, but the type and quality make all the difference. (There are some circumstances, though, in which a low-fat diet may be a good choice.)

Why We Need Fats

Before talking about different types of fats, it's crucial to understand why our bodies need fat in the first place. Dietary fats play several vital roles in human health:

• Energy source: Fats are the most concentrated source of energy, providing 9 calories per gram compared to 4 calories per gram for carbohydrates and proteins

• Nutrient absorption: Fats help the body absorb fat-soluble vitamins (A, D, E, and K) and other important compounds like carotenoids

• Satiety: Fats contribute to feelings of fullness and satisfaction after meals, helping to regulate appetite.

It is also important to appreciate fats as building blocks of our bodies. For example, fats are essential components of cell membranes. Many hormones, including sex hormones and hormones involved in stress responses, are derived from fats. On a macro level, body fat provides insulation and protection, helping regulate body temperature and protecting vital organs. Also, let’s not forget that the human brain is about 60% fat, with a unique fatty acid composition crucial for optimal cognitive function.

Our big brains are also the main reason we rely on fat for energy storage. Because they consume vast amounts of energy – thinking is exhausting – we had to develop a way to store a lot of extra calories to survive and function during prolonged periods of energy deficit. While this is less of a concern for most modern humans, our ability to fatten during good times was a key survival mechanism. As a result, even lean people are still quite plump compared to our closest ape relatives.

Types of Dietary Fats

Dietary fats are typically categorized into four main groups based on their chemical structure: saturated fats, monounsaturated fats, polyunsaturated fats, and trans fats.

Saturated Fats

Saturated fats are solid at room temperature and are found primarily in animal-based foods such as red meat and dairy products (butter, cheese, cream), and some tropical oils (most commonly coconut and palm oils).

For decades, saturated fats were considered universally harmful due to their association with increased LDL (“bad”) cholesterol levels, which in turn increases the risk for cardiovascular diseases. However, some recent studies have questioned this connection. While saturated fats can indeed raise LDL cholesterol, they also tend to increase HDL (good) cholesterol and may shift LDL particles to a larger, less harmful size. The overall impact of dietary saturated fats on cardiovascular risk appears to be moderate or even neutral for most people. Moreover, the exact type of saturated fats seems to be quite important; while animal fats are considered the most problematic, fats in dairy products such as cheese and yogurt may be less harmful or even beneficial.

Contrary to popular belief, some studies suggest that saturated fats may not be as detrimental to weight management as once thought. The medium-chain triglycerides (MCTs) found in coconut oil, for example, may even have some metabolic benefits.

While the demonization of all saturated fats appears to have been an oversimplification, most health authorities still recommend limiting saturated fat intake to no more than 10% of total calories, with some suggesting even lower limits.

Monounsaturated Fats

Monounsaturated fats (also known as MUFA) are liquid at room temperature but may solidify when chilled. They're found in olive oil, avocados, nuts (almonds, cashews, peanuts), and canola oil.

Health effects:

Monounsaturated fats are generally considered heart-healthy and are a key component of the Mediterranean diet, associated with numerous health benefits:

• Cardiovascular health: Monounsaturated fats can help lower LDL cholesterol while maintaining or increasing HDL cholesterol, potentially reducing the risk of heart disease.

• Insulin sensitivity: MUFA may also improve insulin sensitivity, which is beneficial for blood sugar control and diabetes prevention.

• Weight management: Diets high in monounsaturated fats have been associated with lower body weight and reduced central fat distribution.

• Inflammation: MUFAs have been shown to have anti-inflammatory properties.

Polyunsaturated Fats

Polyunsaturated fats (PUFAs) remain liquid at room temperature and even when chilled. They're further divided into two main categories: Omega-6 and Omega-3 fatty acids. These fats are found in fatty fish (salmon, mackerel, sardines), flaxseeds and chia seeds, walnuts, as well as some seed oils such as sunflower, corn, and soybean oils.

PUFAs, particularly of the Omega 3 type, are considered essential because our bodies can't make them, and we must get them from our food.

Health effects:

• Cardiovascular health: Omega 3 fatty acids, especially those from fish oil (EPA and DHA), have been shown to reduce the risk of heart disease, lower triglycerides, and may help regulate heart rhythm

• Brain function: DHA is crucial for brain development and may help prevent cognitive decline in older adults.

• Inflammation: Omega 3s have potent anti-inflammatory effects and may help in managing inflammatory conditions like rheumatoid arthritis.

• Eye health: DHA is a major structural component of the retina and is essential for proper vision.

While both Omega 6 and Omega 3 fatty acids are important, the ratio between them may be crucial. The modern Western diet tends to be very high in Omega 6 and relatively low in Omega 3, which some researchers believe may contribute to chronic inflammation. However, this is still controversial and a topic of active research.

Trans Fats

Trans fats are unsaturated fats that have been chemically altered through a process called hydrogenation. They're found in partially hydrogenated vegetable oils, and some processed and fried foods. Small amounts naturally occur in some animal products

Health effects:

Trans fats are widely recognized as the most harmful type of dietary fat. They are associated with:

• Cardiovascular disease: Trans fats significantly increase LDL cholesterol while decreasing HDL cholesterol, substantially raising the risk of heart disease.

• Inflammation: These fats promote systemic inflammation, linked to various chronic diseases.

• Insulin resistance: Trans fats may contribute to insulin resistance and increase the risk of type 2 diabetes.

Due to their harmful effects, many countries have banned or restricted artificial trans fats in food production. However, it's still important to check food labels, especially those on processed foods.

Balancing Fats in Your Diet

Given all these complexities and the important role dietary fats can play in our health, how should we deal with them in our everyday lives? Here are some evidence-based recommendations:

1. Focus on quality: Choose whole food sources of fat like nuts, seeds, avocados, and fatty fish over highly processed fats.

2. Prioritize unsaturated fats: Make monounsaturated and polyunsaturated fats the primary sources of fat in your diet.

3. Include Omega 3s: Aim to eat fatty fish at least twice a week or consider a high-quality fish oil supplement if you don't consume fish. Also, eat a healthy dose of walnuts and use walnut oil in your cooking.

4. Limit, don't eliminate, saturated fats: While it's wise to moderate saturated fat intake, there's no need to avoid it entirely. Choose high-quality sources when possible.

5. Avoid trans fats: Read labels carefully and avoid products containing partially hydrogenated oils.

6. Consider overall dietary pattern: Dietary fats can and do interact with the other components of your diet. A diet rich in fruits, vegetables, whole grains, and lean proteins provides a healthy context for fat consumption.

7. Individualize your approach: Genetic factors, health status, and lifestyle can all influence how your body responds to different fats. Working with a healthcare provider or registered dietitian can help you develop a personalized nutrition plan.

A balanced approach that includes a variety of healthy fats as part of an overall nutritious diet seems like the best strategy for long-term health and well-being. Remember, no single nutrient or food is a magic bullet for health. Dietary fats should be considered in the context of your overall eating pattern and lifestyle. By making informed choices about the fats you consume, you can support your health and enjoy delicious, satisfying meals..