Are Fats Bad for You? A Dietitian Debunks This Common Nutrition Myth

Uncover how healthy fats support heart health, brain function, and energy

For years, dietary fat has been painted as the villain of good nutrition – blamed for weight gain, heart disease, and many diet-related issues. Low-fat products became the go-to choice, and the belief that “fat is bad” and should be avoided at all costs has been a long-standing nutrition message most of us have heard at some point. In this blog post, we will unpack some of the most common myths about fat and uncover what the research actually tells us. 

Key Takeaways

• Fat doesn’t directly cause weight gain – excess calories from any source can. Including moderate amounts of healthy fats can increase fullness and help stabilize blood sugar, supporting weight management.
• Not all fats are the same. Different types have different effects on health. Prioritize unsaturated and omega-3 fats, limit trans fats, and enjoy saturated fats in moderation.
• The type of fat matters more than the total amount. Healthy fats support heart health, hormone balance, brain function, and vitamin absorption.
• For adults, fat should provide about 20–35% of total daily calories (roughly 45–80 grams on a 2,000-calorie diet). Rather than tracking exact numbers, focus on choosing high-quality fat sources.
• Overall, balance and moderation matter most – prioritize total diet quality instead of fixating on individual nutrients.

Myth #1: Eating Fat Automatically Leads to Weight Gain

This is one of the oldest and most persistent myths in nutrition, and one that many of my nutrition counselling clients share with me as a Registered Dietitian. While fat is the most calorie-dense macronutrient, that alone doesn’t determine how the body uses it. Body weight is influenced by many factors, including overall eating patterns, metabolism, sleep, stress, and movement — not one nutrient on its own.

Changes in body weight are influenced by overall energy balance over time, rather than any single food or nutrient. In fact, including moderate amounts of healthy fats can increase satiety (or fullness), helping you feel satisfied for longer after eating. This can reduce unplanned or less satisfying snacking or cravings that may appear later in the day. 

Additionally, fats help stabilize blood sugar levels, which supports steadier energy and fewer cravings throughout the day. Adding foods like avocado, nuts, seeds, olive oil, or nut butter to meals can support weight management when included as part of a balanced diet.

Importantly, health is not defined by body weight alone. Including fats in a balanced way supports energy, nourishment, and overall well-being.

Myth #2: Fats Are Bad for Your Heart 

This is an oversimplified conclusion to a slightly more complex topic. Not all fats are created equal, and some provide important health benefits, including protecting your heart. Here’s what you need to know about so-called “good fats vs. bad fats”: 

More supportive for health:

Unsaturated Fats

Unsaturated fats (polyunsaturated and monounsaturated fats), found in olive oil, nuts, seeds, avocados, and fatty fish, are considered heart-healthy fats. Including moderate amounts of these in your diet can help lower “bad” LDL cholesterol. 

Omega-3 fatty acids

Omega-3 fatty acids (a type of polyunsaturated fat), found in flaxseed, walnuts, hemp hearts, and fatty fish like salmon, have anti-inflammatory properties and can improve heart health by making the blood less sticky, which reduces the risk of heart attack and stroke. Omega-3 fats can also lower blood pressure and triglyceride levels. Additionally, omega-3 fats are important during pregnancy for brain and nervous system development in babies. Read more about the benefits and sources of omega-3s.

Less supportive when eaten often

Saturated Fats

For years, saturated fats were thought to be harmful to heart health. Saturated fats are found in certain meats (such as red meat or chicken skin), butter, tropical oils like coconut oil, and high-fat dairy foods such as cheese. 

Newer research suggests that saturated fats may or may not increase “bad” LDL cholesterol, which can impact heart health. One reason for these mixed findings is that it depends on what foods replace saturated fat in the diet. When saturated fats are replaced with monounsaturated fats (found in olive oil, nuts, and avocados) or omega-3 fats (found in fish, flaxseed, walnuts, etc.), heart health benefits have been observed. However, replacing saturated fats with high-sugar foods may have a negative effect. What’s important to remember is that health depends on the quality of your overall diet, not just one nutrient. Saturated fats can fit into a healthy diet when enjoyed in moderation. 

Best to limit:

Trans Fats

Trans fats are found in some processed foods (such as cookies, cakes, frozen meals, and deep-fried foods) and in hydrogenated vegetable oils like margarine. Trans fats can increase “bad” LDL cholesterol and lower “good” HDL cholesterol, potentially harming heart health. They may also increase inflammation in blood vessels, raising the risk of other chronic conditions. When possible, try to limit trans fats in your diet. If you’re unsure, check the nutrition label on packaged foods to see if trans fats are present. 

Something Important to Note: 

In addition to the benefits mentioned above, fat is essential for nutrient absorption — particularly fat-soluble vitamins A, D, E, and K. Without dietary fat, your body can’t properly absorb or use these nutrients. 

Fat also plays critical roles in: 

• Hormone production 
• Brain function and mental clarity 
• Cell membrane health 

How Much Fat Do We Need?  

The amount of dietary fat you need each day is based on a percentage of your total calorie intake. The chart below outlines the recommended percentage of calories from fat based on age. These ranges are meant as general guidance, not targets that need to be tracked or perfected.

For example, someone eating around 2,000 calories per day would aim for roughly 45–80 grams of fat. 

The key is to focus on quality sources, not just numbers. Instead of cutting fat, choose nutrient-rich options that support long-term health. 

Practical tip: Include at least one source of healthy fat in every meal – such as olive oil in a salad, avocado on toast, or a sprinkle of nuts over oatmeal. 

Sources of Healthy Fats 

Fat has long been unfairly demonized, but the truth is that your body needs it – for energy, hormones, brain health, and nutrient absorption. 

Rather than avoiding fat, focus on quality and balance by including fats, carbohydrates, protein, and fiber at meals and snacks. Prioritize unsaturated fats, include omega-3 sources, and choose foods that make your meals both nourishing and satisfying. 

Looking for further support in making lifestyle changes? We can help!  

Unsure where to start or feeling stuck on the way? Get connected with one of our dietitians who can support you on your journey. We have a team of experienced dietitians who are passionate about coming along side you and finding personalized solutions to your nutrition challenges.  

Learn more about 1-1 nutrition counselling with a Registered Dietitian or simply contact us to book your discovery call:

Check out these related blogs on our website: