THE SKINNY ON FAT: THE COMPLETE SIMPLETON'S GUIDE TO DIETARY FAT (PART 3)

THE SKINNY ON FAT: THE COMPLETE SIMPLETON'S GUIDE TO DIETARY FAT (PART 3) By Shane Robert

How Much Fat Do We Actually Need?

In Part 1 of this series, we covered what fat is and what it does in the body; in Part 2 we discussed the different types of fats and role they play in adding to, or taking away from, our health. In this third and final part, we will cover how much total fat, and how much of the different fat types, to include in our daily diet. If you need to review the previous installments, click the links above.

A Survival Mechanism Turned Modern Problem: De Novo Lipogenesis

Despite what certain paleo-diet proponents may have you believe, fat simply wasn’t all that prevalent in our ancestral environment. With the exception of wild game meat, which is actually quite lean compared to modern farm raised cattle, and fish, which is also leaner and less common in the diet than one might assume, fat was a rare commodity. Nut trees would be your likeliest source and those are relatively rare without human cultivation, not to mention that nuts aren’t in season all year round. Due to the myriad functions that fat plays in our health, it should come as no surprise that our bodies consider it so important that it can create its own fat. This process, known as de novo lipogenesis (DNL), literally meaning "creating fat anew” (de = from, novo = new, lipo = fat, and genesis = creation), allows fat to be created from excess carbohydrate intake. Given the, comparatively, high availability of carbohydrates in that same ancestral environment, this an ingenious survival mechanism for a species that needs fat but doesn’t always have easy access to it. 

As useful as de novo lipogenesis might have been for our species, in the modern food environment of high carbohydrates, often in the form of sugar, and easy calories, it has become an issue that contributes to many of the population-wide health problems we see in many western nations. Through the DNL process, excess carbs are sent to the liver where they are converted into fat, primarily the saturated fat palmitic acid, and released into the blood stream for circulation in the form of very low density lipoproteins, stored as triglycerides in adipose tissue, or further modified and desaturated to be turned into the unsaturated fat palmitoleic acid. Excess of palmitic acid is one of the reasons that we see blood lipid levels improve in some people on lower carb diets. DNL is not a dominant process in most people under normal diet conditions with adequate dietary fat, however it becomes more active when you consume very high-carb diets in the presence of excess calories and/or if you are insulin-resistant (e.g. metabolic syndrome or type 2 diabetes). 

The Limits of Self-Made Fat: Why We Still Need Dietary Fat

Even though your body can make some fats from excess carbohydrates (via DNL), it cannot synthesize the essential fatty acids ALA (alpha-linolenic acid), an omega-3, and LA (linoleic acid), an omega-6, and these fatsmustcome from diet. See part 2 for more information if you missed it. In addition, as was covered in part 1, fat is needed for absorbing fat-soluble vitamins A, D, E, K, brain and nerve function, hormone production, and cell membrane integrity. For these reasons, a minimum amount of daily fat is needed for optimal health. It is nearly universally agreed by health authorities that an absolute, rock bottom minimum intake of 15-20 grams per day is needed to cover the essential functions above.

General Guidelines: How Much Fat Per Day?

While 15-20 grams per day might be enough to prevent you from developing nutritional deficiencies, optimal health and bodily functioning requires a bit more. To help our bodies be the best that they can be while also having minimal negative side effects, the recommended daily intake is closer to 20-35% of total calories. Below is a table showing the fat ranges, between 20 and 35% of calories, for different calorie levels. 

Personalized Fat Intake: Tailoring to Your Goals

Although 20-35% is a great general guideline, the numbers can change somewhat based on goals. To that end, thinking about fat in terms of grams per/kg of bodyweight can be more useful. In the table below, there are a few different recommended ranges of fat intake for different diet outcomes. 

Choosing Your Range: Practical Examples

Using these guidelines above, a person weighing 70 kg (154 lbs) aiming for general health would eat 56–70 g of fat per day. Even the low end of the range gives this person plenty of fat to optimize all of the various functions fat is needed for. The reason this person might want to eat at the higher end of the range is largely personal. Fat can be a bit more satiating than other macronutrients, for example, so a higher amount can make some people feel a greater sense of fullness. Some of the foods that this person is particularly fond of might come with a higher fat amount attached, such as nuts. It may even fluctuate day to day depending on what foods are eaten or how they are prepared. Or, it could simply be that they subjectively feel better with more fat than less. At the end of the day, so long as this person adjusts their carbohydrate intake to compensate for any additional calories, there will be no issues. 

Quality Matters: The Best Types of Fat to Eat

As covered in part 2, there are 3 main types of fats that can be included in the daily fats consumed. They each serve differing and important functions in the body and should make up a portion of your daily fat intake. Far and away the most important fat, the one that should make up the predominance of your daily intake, is monounsaturated fats, followed by polyunsaturated fats, with an emphasis on omega-3 PUFAs, and finally, the lowest percent, though still important, saturated fats, ideally from natural sources like grass-fed meats and dairy, rather than processed foods.

Putting It All Together: A Simple, Balanced Approach

Using the example of our 70kg person, and assuming they eat around 2300 calories per day to maintain their weight, their fat intake will fall somewhere between 50-90 grams per day. MUFAs will, ideally, be 25-55 grams per day, PUFAs will be 10-27, and SFAs between 5 and 27 depending on the total daily fat grams and percentage given to each fat type. Fortunately, if the foods that our example person chooses are largely whole and unprocessed from natural sources, like pasture raised/grass-fed, and include a variety of things, it shouldn’t take a lot of forethought to follow these ratios. 

Final Thoughts: Fat Isn’t the Enemy

Fat is an absolutely necessary part of our diet. Without enough of it, we will eventually die. Hopefully the knowledge gained from this series will help clear up any misunderstanding or confusion that may have existed when it comes to this macronutrient. It doesn’t need to be complicated or confusing. It’s just food and we humans have been eating it for a very, very long time.