Macronutrients, Part 4: Why Fat Matters (and Why Cutting It Backfires)

In this nutrition series, we’ve already talked about calories, protein, and carbohydrates.

Now it’s time to tackle the macronutrient that’s been misunderstood, feared, and unfairly blamed for decades:

Fat.

Somewhere along the way, fat got labeled as “bad.”

Low-fat became synonymous with “healthy.”

But for athletes — and honestly, for humans — fat isn’t optional. It’s essential.

What Fat Actually Is (and Why Your Body Stores It)

Like carbohydrates, fats are made of carbon, hydrogen, and oxygen. But structurally, they behave very differently.

Carbohydrates are water-loving and stored with water.

Fat is water-repelling and extremely energy dense.

• Fat provides 9 calories per gram
• Carbs and protein provide 4 calories per gram

That means fat is your body’s most efficient way to store energy.

This is why you can go hours between meals.

It’s why you don’t need to eat every 90 minutes to survive.

It’s why even lean athletes carry tens of thousands of calories of stored energy.

Fat is your long-burn fuel.

Different Fats, Different Jobs

Fats are made up of fatty acids — long chains of carbon atoms. Some are short, some are long, and some are very long. These chains usually travel together in groups called triglycerides.

Where it gets interesting is how these chains are structured.

Saturated vs. Unsaturated Fats (The Simple Version)

Think of a fatty acid chain like a long table:

• Saturated fat = every seat is filled
  • Straight, stable, orderly
  • Solid at room temp (butter, tallow, coconut oil)
• Unsaturated fat = some seats are empty
  • Creates bends or “kinks”
  • Liquid at room temp (olive oil, avocado oil)

One kink = monounsaturated

Multiple kinks = polyunsaturated

Those bends matter — because they make fats more fragile.

Why Some Fats Break Down (and Cause Problems)

The more “kinks” a fat has, the easier it is for oxygen to sneak in and cause damage. This process is called oxidation.

When fats oxidize:

• They become unstable
• They create inflammatory byproducts
• They can damage surrounding cells

Polyunsaturated fats — especially when extracted from seeds and industrially processed — are the most fragile. Heat, light, and air accelerate the damage.

This doesn’t mean all unsaturated fats are bad. It means processing matters.

Whole foods protect fats. Factories don’t.

A Word on Trans Fats (Just Avoid Them)

Trans fats were created through hydrogenation — a process originally developed for industrial lubricants, not food.

Food manufacturers used it to:

• Make cheap oils solid
• Extend shelf life
• Replace butter and lard

The result? Margarine, shortening, and a chemistry experiment that went very wrong.

Trans fats:

• Disrupt cell membranes
• Increase inflammation
• Significantly raise heart disease risk

They’re now banned in many places — but they still sneak into ultra-processed foods and imported products.

If you see “hydrogenated” or “partially hydrogenated” oils on a label, put it back.

What Fat Is Actually Used For

Fat isn’t just stored energy.

It plays massive roles in:

• Building cell membranes
• Producing hormones (testosterone, estrogen, cortisol, vitamin D)
• Supporting brain and nervous system function
• Absorbing vitamins A, D, E, and K
• Protecting organs and insulating the body

Cut fat too low and these systems start to suffer — quietly at first, then loudly.

Essential Fatty Acids (The Ones You Must Eat)

Some fats are essential, meaning your body cannot make them.

There are two:

• Omega-6 (linoleic acid)
• Omega-3 (alpha-linolenic acid)

They support:

• Cell membrane integrity
• Brain and nervous system function
• Immune response
• Inflammation regulation

Deficiency is rare — but possible when fat intake is extremely low or absorption is impaired.

And while you only need a small amount to prevent deficiency, very low-fat diets create other problems.

What Happens When Fat Intake Is Too Low

This is where things start to fall apart.

1️⃣ Hormones Take a Hit

Fat and cholesterol are raw materials for hormones.

Too little fat can lead to:

• Low testosterone or estrogen
• Poor stress tolerance
• Fatigue
• Mood changes
• Irregular cycles

2️⃣ Vitamins Don’t Absorb Well

Vitamins A, D, E, and K require fat.

Low fat → poor absorption → subtle deficiencies that show up as:

• Weak bones
• Low immunity
• Poor recovery
• Easy bruising
• Vision issues

3️⃣ Cells and Nerves Suffer

Even “non-essential” fats help maintain:

• Cell membrane health
• Nerve signaling
• Muscle contraction
• Recovery from training

4️⃣ Hunger Goes Through the Roof

Fat slows digestion and keeps you full.

Too little fat often leads to:

• Blood sugar swings
• Constant hunger
• Over-reliance on refined carbs
• Feeling unsatisfied no matter how much you eat

5️⃣ Inflammation Can Increase (Ironically)

Low-fat diets are often high in refined carbs and omega-6 seed oils — which can actually increase inflammation, not reduce it.

The Big Picture

Fat isn’t the enemy.

It’s a tool.

Carbohydrates are your high-octane fuel.

Protein builds and repairs.

Fat provides structure, hormones, and long-lasting energy.

Like every macronutrient, quality and context matter.

Choose fats from real, minimally processed foods:

• Eggs
• Meat
• Fish
• Full-fat dairy
• Avocados
• Olives
• Nuts and seeds
• Natural oils used gently

Avoid industrial experiments pretending to be food.

Your body is incredibly complex — and it needs all three macronutrients working together to thrive.

Understand fat. Use it wisely.

Next up, we’ll tie this all together so you can actually apply it without overthinking.

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