My last two posts have been on protein and carbohydrate. So this week we’re going to look at the last macronutrient: Fat. Now “fat” gets a bad rep and I’ve absolutely no doubt that you’ve been told that “fat is bad for you” at least once. But then you hear about people following high-fat diets and losing weight and how does that work? And it’s all just a bit weird and confusing right? The truth is actually quite simple: fat is essential for your body and your health, and the key is understanding what kinds of fat to eat, how much, and what fat does for the body.

So today, let’s clear up the confusion about fat as a macronutrient. Whether you’re looking to lose weight, build muscle, or simply eat healthier, understanding fat can help you make smarter food choices and feel better in your body.

What Is Fat, Exactly?

As I said above, fat is one of the three main macronutrients, alongside carbohydrates and protein. Macronutrients are the nutrients we need in large amounts to provide our bodies with energy. Without going into too much of a chemistry lesson, fats are made up of fatty acids, which are chains of chemicals. The nature of the chain decides the properties (type) of fat – for example if it’s a liquid or a solid at room temperature. The body needs fatty acids for many of its critical functions, and while it can manufacture most of them from other foods, there are a few that we can only get by eating fat. So there’s our first reason for including fat in a balanced diet.

Fat is the most energy-dense of the three macronutrients, providing 9 calories per gram, compared to 4 calories per gram for both carbs and protein.

From a biological standpoint, fat plays a number of crucial roles:

• It serves as a long-term energy source
• It helps with hormone production
• It aids in the absorption of fat-soluble vitamins (A, D, E, and K)
• It insulates and protects our organs
• It forms part of every cell membrane in your body

So, while fat often gets a bad rap, your body literally cannot function properly without it!

The Different Types of Fat

On that note, then, here’s a quick breakdown of the different types of fat and how they affect your body.

1. Unsaturated Fats

Unsaturated fats are generally considered heart-healthy and anti-inflammatory. They come in two types:

• Monounsaturated fats – Found in olive oil, avocados, and certain nuts like almonds and peanuts.
• Polyunsaturated fats – Found in fatty fish (like salmon and mackerel), walnuts, flaxseeds, chia seeds, and sunflower oil.

Omega-3 and omega-6 fatty acids are polyunsaturated fats. Omega-3s are especially beneficial for heart and brain health, while omega-6s, though essential, should be balanced with omega-3 intake to avoid promoting inflammation.

2. Saturated Fats

Saturated fat has long been blamed for heart disease and other issues. However the picture is a bit more nuanced than we used to think (of course). While excessive intake can raise LDL cholesterol (low-density lipoprotein – “bad” cholesterol), saturated fats are found naturally in some foods that comes from animal sources, like some meat and dairy, and recent research suggests that moderate consumption of saturated fats from whole food sources like eggs, cheese, and coconut oil may not be as harmful as once thought—especially in the context of an otherwise balanced diet. The UK Government suggests women should not eat more than 20g of saturated fat per day, and 30g for men.

A look at the type of foods containing saturated fats maybe gives a wee clue about the fact that we should keep saturated fats to a minimum though:

• Fatty cuts of meat
• Sausages and pies
• Butter and lard
• Cheese, cream and ice cream
• Biscuits, cakes and pastries

The key with saturated fat is moderation and context. It’s better to get it from real, minimally processed foods rather than ultra-processed ones. And as always, if you have issues with high cholesterol make sure to speak to your doctor, and get advice on your diet from a professional who knows your specific circumstances.

3. Trans Fats

While I’ve spent this post saying nice things about fat and how it is important for your body to function, there is always an exception. Artificial trans fats, often listed as “partially hydrogenated vegetable oils” on labels, are that exception, and you should try to avoid these as best you can. They raise LDL cholesterol, lower HDL cholesterol (High-density lipoprotein – “good” cholesterol), and increase inflammation. They’re found in some processed baked goods, fried foods, and margarine spreads.

Many countries have banned or restricted trans fats, and most of the supermarkets in the UK have removed trans fats from their own-label food — but they can still show up in some packaged foods, so it’s worth checking the label. UK Government guidelines suggest adults should not consume more than 5g of trans fats per day.

Why Your Body Needs Fat

We talked about this briefly before, but let’s look a wee bit closer at some of the reasons why fat is not just beneficial—but essential.

1. Hormonal Health

Fat is vital for hormone production and regulation. This is especially important for people who are active or working out regularly. Hormones like testosterone, estrogen, and cortisol are synthesized from cholesterol and fatty acids. If you don’t get enough fat, your hormonal balance can suffer, which can affect everything from mood and energy levels to muscle recovery and sleep quality.

2. Vitamin Absorption

As I mentioned earlier, some vitamins are fat-soluble—meaning they need dietary fat in order to be absorbed by the body. Without enough fat, you could eat plenty of foods rich in vitamins A, D, E, and K, but your body wouldn’t be able to use them efficiently. These vitamins are important for things like immune function, bone health, and healthy eyes and skin.

3. Brain Function

Your brain is about 60% fat. Essential fatty acids like omega-3s are crucial for cognitive function, memory, and even mental health. Deficiencies in healthy fats have been linked to depression, anxiety, and brain fog.

4. Satiety and Satisfaction

Fat also plays a role in how full and satisfied you feel after eating. Meals that include healthy fats tend to keep you fuller longer, which can help prevent overeating and make sticking to your nutrition goals easier. That’s why I always encourage clients not to fear fat—instead, learn to include it in healthy amounts and from good sources.

How Much Fat Should You Eat?

I’ve listed the UK guidelines for Saturated and Trans fat above, but the total amount of fat you need depends on your sex, body size, activity level, and overall goals. Here are some general guidelines:

• Fat should make up around 20–35% of your daily calorie intake.
• For someone consuming 1800 calories per day, that’s about 360-630 calories worth of fat per day.
• At 9 calories per gram, that works out as 40-70g of fat per day

If you’re on a lower-carb or ketogenic diet, your fat intake might be higher. On the other hand, if you’re eating more carbs for performance or endurance training, your fat intake might be on the lower end of that range.

As a personal trainer, I often recommend clients aim for a balanced approach, including healthy fats at most meals. You don’t need to count every gram unless you’re working with specific goals—but having a general idea of the amount and type of fat you’re eating helps.

Good Sources of Healthy Fats

Here are some excellent whole-food sources of healthy fats to incorporate into your diet:

• Avocados

Packed with monounsaturated fats, fiber, and potassium. Great in salads, smoothies, or on toast.

• Fatty Fish

Salmon, mackerel, sardines, and trout are high in omega-3s, which support heart and brain health.

• Nuts and Seeds

Almonds, walnuts, chia seeds, flaxseeds, and sunflower seeds provide healthy fats, protein, and micronutrients. Great for snacks or toppings.

• Olive Oil

A staple of the Mediterranean diet, olive oil is rich in monounsaturated fats and antioxidants. Use it for salad dressings or drizzling over roasted veggies.

• Full-Fat Dairy

Full-fat yogurt, cheese, and milk can be part of a balanced diet and provide both saturated and unsaturated fats.

• Eggs

Egg yolks contain healthy fats, vitamins, and choline—important for brain health. Yes, the yolk. Eat the whole thing, not just egg whites.

Common Myths About Fat – Busted

Let’s wrap up by busting a few lingering myths about fat:

❌ Myth #1: Eating Fat Makes You Fat

Nope! Excess calories lead to fat gain—not fat itself. In fact, healthy fats can help regulate appetite and support fat loss when included in a balanced diet.

❌ Myth #2: Low-Fat Diets Are Healthier

That’s a very sweeping statement. While some people might do well on, or need a low-fat diet for medical reasons, everyone is different. Cutting out all fat can lead to vitamin deficiencies, hormone imbalances, and cravings. IMHO balance is better than restriction.

❌ Myth #3: All Saturated Fats Are Bad

Saturated fat from whole foods like eggs or grass-fed dairy isn’t the same as the fat found in ultra-processed junk. Context matters, amount matters, and your own personal circumstances matter.

Final Thoughts

If you’ve been avoiding fat because you thought it was the enemy, it’s time to rethink that relationship. Fat is a powerful, essential macronutrient that supports your hormones, brain, metabolism, and overall health.

Hopefully you now understand the difference that embracing healthy fats can make—not just physically, but mentally and emotionally, too. When you fuel your body with the right kinds of fat, you’ll feel more energised, satisfied, and in tune with your goals. But type and amount matters. So hopefully you’ve got a bit more of an understanding about fat and can see it’s not an enemy to avoid at all costs.

As always, this is general information, and if you have a concern about your diet or a medical issue (like high cholesterol) please get it checked out.

If you want help building a balanced, realistic nutrition plan that includes the right fats for your body and goals, I’m here to support you. Let’s make food work with you, not against you.