When it comes to dietary fats and carbohydrates, advice has varied greatly. The good news is that we do have long-standing wisdom just about everyone can follow for better health. 
 
Why We Need Fats In Our Diet
Fats are a high-energy fuel source and a necessary macronutrient for all of us. They satisfy hunger, help sustain energy for longer periods of time and serve as our go-to fuel when exercising. People who remove fat from their meals get very hungry throughout the day.
 
Three Types of Fats, Different Health Effects
 
Unsaturated fat is typically considered the healthiest of the three types of fats as it provides health benefits such as lowering cholesterol, strengthening the cell membrane, and facilitating storage of vitamins A, D, E, and K. Unsaturated fats are liquid at room temperature; the best source comes from plants such as avocado oil or olive oil. 
 
Saturated fat’s benefits vs risks is controversial. If you have diabetes or heart disease, you may need a diet overhaul, but you may want to limit your intake of saturated fat. This type of dietary fat can have a negative effect on cholesterol especially when it is part of an otherwise unhealthy diet.  However, it can be important for helping maintain cell membrane integrity and brain health. Most saturated fats come from animal sources and are solid at room temperature. One plant-based saturated fat is coconut, which has health benefits and is useful in many types of cooking. How much saturated fat YOU need in your diet is something I recommend  you discuss with your Functional Medicine physician or other holistic provider. 
 
Trans fat (aka trans fatty acids) is the fat you want to keep out of your diet. Trans fats are found in all processed foods. On a food label, trans fats go by many names including “hydrogenated” or “partially hydrogenated.”
 
To learn more about these fats visit this article from Chris Kresser. 
 
What about Essential Fatty Acids?
Omega-6 and omega-3 fatty acids are polyunsaturated fatty acids, meaning they contain a unique chemical structure. When it comes to your health, EFAs are absolutely essential to a number of functions in the body. They play a crucial role in fetal brain development, provide protective benefits for the heart and nerve tissue as we age, and reduce inflammation. EFAs are found in fish, walnuts and flaxseed among other foods. 
 
And What About Carbs?
Carbohydrates are another essential macronutrient (protein completes the macronutrient group). In the body, carbs are converted into different sugars, making them a necessary fuel source. For example, glycogen is the fuel for muscles to work hard during exercise. Glucose is the fuel source for the brain. Your body needs carbs; they are not the enemy of a healthy diet.
 
Fruits, vegetables, and legumes are sources of carbohydrates that provide necessary vitamins and minerals. Whole grains such as oats, whole wheat, and barley also contain carbs. The food source of your carbohydrates and how it acts in the body is important. Some carbohydrates, like whole grain oats, are slow-acting–they do not rapidly spike blood sugar levels, leading to that ‘crash’ feeling. 

What does give you that crash and burn feeling? Carbohydrates from simple sugars, like sucrose, which is found in white table sugar and is added to many packaged foods and baked goods. This is the sugar you want to minimize, if not eliminate from your diet. Whether it’s a blueberry muffin or a candy bar disguised as a protein bar…the villain among carbs is found in packaged and processed foods.
 
Most Valuable Nutrition Tip
The most valuable nutrition tip you could follow for any meal is this: 

Include a source of healthy fat (avocado or Extra Virgin Olive Oil), a lean protein, a whole grain carb (quinoa, brown rice, sourdough), and a rainbow of fruits and veggies on your plate. 

If you are unsure of how to plan the best diet for you, one that provides all that you need and that you enjoy eating, consider working with someone trained in this area. A holistic practitioner can serve as an excellent health care partner to help you navigate the nutrition and food journey. 

Resources
Mayo Clinic: “Dietary Fat.”
Oregon State University Nutrition Glossary: “Fatty Acids”
Washington State University: “Nutrition Basics”