The Ultimate Guide to Dietary Fat

The ultimate evidence based guide to dietary fat for women's health, sports performance and weight loss.
The ultimate evidence based guide to dietary fat for women's health, sports performance and weight loss.

Fat might be the most misunderstood food group. Many people are confused about how fatty foods affects their health whilst other people are scared to eat them at all. With the countless number of sensational headlines regarding our favourite breakfast meats, buttery spreads or condiments, it’s no surprise that we are bewildered about the fat in our diets. If you are looking for clarity on dietary fat for health, sports performance and weight loss than this article is for you. This guide to dietary fat discusses the most common questions with explanations that are back by science so that you can make informed decision about your diet.

What is Dietary Fat?

Dietary fat is one of three macronutrient we need in our diets in large amounts, alongside protein and carbohydrates. Each gram of fat contains 9 calories, making it the most energy dense macronutrient. The body uses dietary fat in several ways; as fuel for energy, for digestion of vitamins and supporting hormone production.

Fat has been demonised for the past few decades. Many people believe that fat is bad for your health or that eating fat will make you fat – but it’s not that simple! Fat is not inherently unhealthy or fattening. As with the other macronutrient like protein and carbohydrates any excess of calories from fat will lead to weight gain. With that being said, dietary fat is the macronutrient most easily turned into body fat when we overeat calories. This is because it requires less energy to digest dietary fat but also because our bodies will prioritise using carbohydrate for energy over fat. Furthermore dietary fat can be easily over consumed as it is more energy dense and less satiating than high fibre or high protein foods.

Fats are made up of repeating fatty acid units or fatty acid chains. There are two types of fatty acids: saturated fatty acids or unsaturated fatty acids. The determinant of whether a fat is saturated or unsaturated, is the number of double carbon bonds.

Saturated Fats

Saturated fats (SFs) are fats which are solid at room temperature such as coconut oil, dairy products or meat. However this is not always the case for example milk & cream contain saturated fat but are not liquid at room temperature. Saturated fats contain no double carbon bonds in any of it’s fatty acid chains. As a result saturated fats tend to be harder to digest than unsaturated fat. The lack of double carbon bond also mean they are more stable and store better than unsaturated fats.

Example of saturated fat:

  • Egg yolks
  • Dairy: milk, cream, butter and cheese
  • Coconut and palm oil
  • Fatty meats: beef, lamb, pork and some chicken products
  • Lard

Are saturated fats bad for your health?

It’s been hotly debated within the scientific community whether or not saturated fats are bad for your health. Although some studies and meta-analysis support the opinion that saturated fat can be included in a healthy balanced diet. Other studies conclude that too much saturated fat in a diet is unhealthy, particularly to heart health. Although saturated fat increases heart disease risk factors, there is currently not enough evidence to support that saturated fat inherently causes heart disease. Saturated fat intake in isolation can not be viewed as a sole indicator of a healthy diet. Therefore the best way to reduce risk of heart disease is by improving the quality of your overall diet and not by simply restricting one macronutrient.

Unsaturated Fats

These types of fat are generally healthy fats which are protective of the heart (with the exception of trans fats). Typically these fats are liquid at room temperature in oil form however they are also occur in solid food too. Unsaturated Fats contain one or more double carbon bonds. This group of fats can be further broken down into Monounsaturated Fats (one double carbon bond) and Polyunsaturated Fats (two to six double carbon bonds).

Monounsaturated Fats

Monounsaturated fatty acids (MUFAs) are healthy fats. These fatty acids have a single double carbon bond, making them easier to digest than saturated fats. Studies have shown that diets rich in MUFAs have positive effects on insulin sensitivity and prevalence of diabetes. The Mediterranean diet is high in MUFAs, the main source of fat in this diet is olive oil. Multiple studies have shown that the Mediterranean diet helps to prevent and manage heart disease and type 2 diabetes. Monounsaturated unsaturated fats may also aid in reducing inflammation and risk of cancer.

Examples of monounsaturated fats:

  • Olive oil
  • Vegetable oils
  • Avocados
  • Nuts & nut butter
  • Seeds

Polyunsaturated Fats

Polyunsaturated fats (PUFAs) are another type of healthy fat. These fatty acids have two to six double carbon bonds, making them the easiest to digest. PUFAs typically come from plant sources and oily fish. Essential fatty acids such as Omega-3 and Omega-6 fatty acids are types of PUFAs. These fatty acids can not be made by our body so we need to get them from our food. People tend to be deficient in Omega-3 fatty acids but often get enough Omega-6 fats from their diets. Meta analyses have shown that replacing saturated fats with polyunsaturated fats is associated with a lower risk of heart disease. PUFAs can also help lower bad cholesterol.

Example of polyunsaturated fats:

  • Fatty fish: salmon, sardines, tuna, trout, mackerel and herring
  • Flaxseeds, sesame seeds and sunflower seeds
  • Walnuts, pinenuts
  • Corn, flax, soybean and safflower oil

Trans Fat

Whilst the other unsaturated fats are generally healthful (when eaten in moderation in a balanced diet), artificial trans fats are unhealthy unsaturated fat which should be avoided. Artificial trans fat have been shown to negatively impact health. In studies they have been linked to increased heart disease risk factors, increased inflammation and bad cholesterol – more so than any other macronutrient.

Examples of food which may contain trans fat:

  • Deep fried fast foods: french fries, chips, doughnuts
  • Margarine and vegetable shortening
  • Baked goods: cakes, cookies and pastries
  • Processed snack food

What are the benefits of eating fat?

Strong immune system

Supporting the immune system & reducing inflammation

Dietary fat particularly polyunsaturated fat contribute to immune and inflammation function. Essential fatty acids are required for growth and maintenance of immune cells. It’s important to note that, both type of fat intake and total fat intake both influence the activity of immune cells (as some studies have found reduction in total fat have been also shown to enhance immune response). In studies high Omega-3 intakes are also associated with reduced inflammation.

Some fats are good for your heart

Studies have shown that swapping saturated fats and/or refined carbohydrates with polyunsaturated fats lower risks of heart disease. Diets including high intakes of monounsaturated fat also prevent and manage heart disease and type 2 diabetes.

Supporting the absorption of vitamins

Fat soluble vitamins

Fat is required for the digestion, absorption and transport of fat soluble vitamins; vitamins A, D, E & K. It’s essential to consume fatty food so that your not deficient in these micronutrients. These vitamins are key in several key body function such as brain function, bone maintenance and immunity.

Supporting hormonal balance

Hormones are formed from fat and cholesterol and therefore a lack of fat has an adverse effect on hormone production and hormonal balance. Cholesterol is key in the production of our sex hormones; progesterone, estrogen and testosterone. Healthy fats also help maintain balance of hormone involved in appetite, metabolism and satiety.

Fat is an efficient energy source

The energy density of fat and our bodies ability to store fat, makes fat the most energy efficient macronutrient. Fat can be used as fuel by our bodies when we need extra energy. Fat is a key energy source low to moderate intensity or endurance exercise as our bodies can only store limited amount of carbohydrate for energy.

How much fat should I be eating?

The number of calories and subsequently fat you need is dependent on a number of factors, such as your weight, body composition, goals and training amount & style. However, with regards to setting up your total calorie and macronutrient goals, it is key to prioritise protein intake (more on protein here).

After you’ve figure out the amount calories as well as protein you need, you can essentially split the remainder of calories between dietary fat & carbohydrates. General guidance is to have between 20-35% of daily total calorie from dietary fat. Aim to get for no more than 10% of total calories from saturated fats. Ensure your total fat intake is no less than 20% of calories as extremely low levels of fats can lead to hormonal issues.

What kind of fats should I be eating?

Prioritise eating healthy polyunsaturated and monounsaturated fats as these fats are good for your heart. Eat saturated fat in moderation and try to avoid eating trans fats. Whilst unsaturated fats are healthful, they are still calorically dense so be mindful about the amount you eat.

Do low fat diets work for fat loss?

Low Carb vs Low Fat Diets

Studies find that both low fat and low carb diets can work for weight loss (where calorie intake is below maintenance levels). Whilst reducing fat can be an effective strategy to lose fat, a lot of low fat products contain unhealthy highly refined carbohydrate instead. If you are going on low fat diet, avoid eating highly processed low fat food and try to eat more lean whole food sources.

Adherence, sustainability and success of any diet is dependent on your lifestyle, personality, preference and preparedness. Low fat diets are just one of many weight loss strategy which some people may benefit from. However, it also possible to eat fat in moderation as part of a caloric deficit and lose weight.

Keto diet, high fat diet

What about high fat diets such as the keto diet?

The Keto or Ketogenic diet is a high fat, very low carbohydrate diet. The aim of the Keto diet is to reach a state of ketosis where body fat is being used as fuel. The Keto diet is primarily made up of food like fatty meats & fishes, full-fat dairy, oils, nuts & seeds and non-starchy vegetables. Carbohydrates are typically limited to less than 50 gram a day and moderate amounts of protein are consumed. In studies the keto diet has been proven to assist in weight loss and improve health markers. It’s also been used medically to aid in the treatment of various condition such as seizures, multiple sclerosis and Parkinson’s.

If you are going to increase the amount of fat you eat, then it’s key to ensure that you’re eating the majority of fat from good quality sources. Prioritise eating heart healthy unsaturated fat and unprocessed fatty foods. Include nuts, seeds, green leafy and non-starchy vegetables in your meal plans and consider supplementing with vitamins and minerals to prevent nutrient deficiencies.

Should I supplement Omega-3 or fish oils?

Omega-3 Supplements

Whilst it’s preferential to get omega-3 from your diet, supplements may be beneficial to individuals who may not get enough essential fatty acids from their food. If you’re already including 2 or more serving of fatty fish a week in your diet than it may not be necessary to supplement with omega-3 or fish oils. However, if you don’t eat fish consider taking a omega-3 or fish oil supplement. For individuals with fish allergies or on a plant-based diet there are also algae-based supplements which can boost your omega-3 intake.

Nayomi Pennant
I’m an utter foodie who is passionate about wellbeing, health & fitness. I created Her Food and Fitness to share delicious nutritious recipes & feasible fun fitness advice for women. My mission is to provide women with food and fitness advice on how to lose fat, build lean muscle and stay healthy.