I saved the best macronutrient for last – fat! There’s a lot of confusion about fat and its role in our health. Are you behind on your reading? Be sure to check out part 1 (carbs) and part 2 (protein) .

As with the other macros, when we talk about dietary fat, we’re really looking at categories and chemistry.

There are 4 main types of fat based on chemistry: 

• Saturated fat
• Trans fat
• Monounsaturated fat
• Polyunsaturated fat 

The terms saturated vs unsaturated fat refers to their chemical structures. All fats are made of smaller molecules – glycerol and fatty acids. But saturated fats tend to be saturated with hydrogen molecules whereas unsaturated fats have a double bond. This changes how the fat is processed by the body. 

What do fats do? 

The chemistry and the type of fat makes a different in how that nutrient is used by our body. All fats are turned into lipids and are later repackaged as lipoproteins to help our body: 

• Transport, absorb, and store vitamins A, D, E, and K
• Are a major contributor to sex hormone production and corticosteroids
• Form the outer layer of every cell on our body (aka, the phospholipid bilayer)
• Source of essential fatty acids omega 3 and omega 6 (remember, essential means our body can’t make it – we have to get it from food)
• Omega 3 fatty acids reduce inflammation in the body
• Form much of the brain
• Taste amazing

We get these benefits from all fats – not just the “healthy” ones. 

Fats that we eat do NOT become body fat. Dietary fat is very dense – it has the highest energy per gram (9kcal/g) compared to carbs and protein (4 kcal/g). This is great for anyone who needs a lot of calories but has a small appetite. Fats are crucial for the brain development of children and adolescents. Additionally, fat is satisfying and digests slowly which reduces our cravings for sweets.

Fat is not the enemy. 

The only real danger of dietary fat is when we eat an imbalanced amount OR inadequate fat. 

How much do I need?

In general, our bodies thrive when fats are at least 25% of our calories. For a 2000 calorie diet, that’s at least 55 grams of fat per day (of any type of fat). 

Saturated fat

For heart health, the American Heart Association recommends limiting saturated fat to 5-6% of calories. That’s about 11-13 grams / day. Other organizations recommend < 10% of calories from saturated fat (or 22-26 grams / day) for a 2000 calorie diet. There is no immediate health consequences to having more saturated fat than this. Like many nutrition guidelines, we use these numbers as reference points, not rules. If someone is really far above the mark chronically, it can contribute to changes in cholesterol production.

Saturated fats are primarily found in higher percentages in animal products (meat, dairy) and some tropical plants (coconut, palm oil). 

Polyunsaturated and Monounsaturated fat

Unsaturated fats tend to get lumped together when it comes to recommendations. Ideally these fats should make up the majority of the types of fat eaten and our bodies prefer if we eat a variety of sources. 

These are primarily found in plant and fish sources of fat. 

Trans fat

Trans fat or “partially hydrogenated oils” are rough on cholesterol production. It’s best to limit as much as possible.  Generally, trans fat was found in many snack food products (cakes, cookies, crackers, chips, peanut butter) and fried foods. Much of the trans fat has been removed from the food supply in the United States, so there’s less need to be hypervigilant around this.

Where are the types of fat found? 

Most foods with dietary fat are a combination of saturated and unsaturated fats. The percentage of saturated and unsaturated fat varies. It’s best if most of the fat we eat is primarily unsaturated but it’s impossible (and unnecessary) to strictly avoid saturated fats.

Composition of common fat sources. Source: Nutrition Action Newsletter

What should I eat? 

I don’t recommend anyone start trying to count the number of grams of fat they eat each day. Additionally, just because a food is higher in saturated fat does NOT mean it needs to be avoided! The “best” choices depend on eating preferences and styles. 

In general the goals are to:

1. Avoid trans fat
2. Limit  / be reasonable saturated fat
3. Enjoy more unsaturated fats

It’s about balancing your overall food choices. Here are some of the most common food questions I get in clinic. 

What about “seed oils?”

This is a topic coming up more in the early 2020s. Some folks claim that “seed oils” should be avoided due to their link to inflammation within the body. Some go so far as to call them “toxic.” Like many claims, there is a hint of science here but a lot of misconception. Seed oils are known to be higher in omega-6’s (a type of polyunsaturated fat). While there is a degree to which they can cause inflammation, they are also a type of essential fat that the body needs. Not all inflammation is “bad.” What we want is to also give the body tools that are “anti-inflammatory” to create a balance.  As you can see from the image above, some fats do have a higher percentage from omega 6’s, but none are 100% one type of fat. “Seed oils” take the brunt of the blame, but it really is ok to have them in reasonable amounts. Things may get more tricky if seed oils make up most of the fat in your diet.  If you want to dig in more, here’s some research. 

Should I have butter or margarine? 

It depends on your overall diet. 1 T of regular butter comes in at 7 grams of saturated fat (1/2 of what you need in a day). However, if you don’t eat much total saturated fat (and don’t eat much butter), there’s nothing wrong with regular butter. However, if you love putting that butter flavor on everything and/or want to keep other high fat animal products in your life, you may consider switching to a trans fat free plant based margarine. 

What is the best kind of nut?

There are benefits to every nut. From a type of fat perspective, almonds and walnuts have higher amounts of unsaturated fats – particularly omega 3s. However, they’re also more expensive making them not accessible to everyone. Don’t be too quit to rule out peanuts as a great source of fat. 

What kind of milk / yogurt should I get? 

Whole fat dairy is rarely a deal breaker for a healthy diet, unless you’re drinking truly excessive amounts. Additionally, having fat in milk allows your body to absorb more vitamin D (and calcium!). 

What should I know about meat? 

All meat has saturated fat. The leaner the meat, the less saturated fat it has. In general from highest to lowest saturated fat: 

• High fat deli meats (hot dogs, bacon, sausage, pastrami, salami, brats, bologna)
• “Red” meat (cuts of beef)
• “Pink” meats (pork, goat)
• “White” meat (chicken, turkey, white fish)

Just because something has more saturated fat, doesn’t make it off limits. Our bodies can tolerate more saturated fat in a day. What matters most is the balance over time. 

What about coconut oil? 

Pop culture diets treat coconut oil like a super food. While it has some benefits and unique properties, “more” isn’t better. Nor is it wise to make it your only source of fat. Coconut oil is high in saturated fat. But the chemistry / bond is different than the saturated fat found in animal products. The research is not clear whether or not that means we metabolize it differently. In general, if you want to use it, keep the amount small. 
Want more information? Check out this article on Today’s Dietitian. 

Moral of the story…

Dietary fat is essential for the body and does so much for our health. It’s best if we get most of our fat from plants and fish but that doesn’t mean we need to avoid fat from animals – just don’t go overboard.