Why Low-Fat Diets Can Hurt Performance and Recovery

G'day mate!

I'm still blown away that we finally have someone who broke the sub-2 hour marathon mark in a sanctioned race. Running a 4:26 mile for 26 miles. Crazy. I did a 2 hour bike effort on Sunday and realised this bloke ran around London in less time.

It got me thinking about what it takes to sustain that output—the training, the recovery, the fuel. And one of the biggest levers athletes at every level get wrong? Fat. The low-fat era left a mark people are still living with, quietly wrecking performance and recovery in ways most don't connect.

In this week’s newsletter (4 min read): 
🧠 Why fat is essential for hormone production & what happens when you cut it too low
⚡ How low dietary fat tanks energy, blunts adaptation, and kills performance
🥑 The fats worth prioritizing—and the practical way to think about them

If you have a mate still eating low-fat yogurt wondering why they're always tired, send them THIS link.

Fat Isn't the Enemy

The low-fat movement came from real research and real fear. What we weren't told is that when manufacturers pulled the fat, they replaced it with sugar. We traded one problem for a much bigger one and called it healthy.

Think of it like a sports team. Carbs are your star striker. Protein is your defender. Fat is the entire back office — physio, sports scientist, recovery staff. Not on the scoresheet, but pull them out and the whole operation falls apart.

What fat actually does:

• Produces testosterone, estrogen, and cortisol

• Makes up 60% of your brain structure

• Lets you absorb vitamins A, D, E, and K

• Fuels zone 2 training and long runs

When fat drops too low alongside insufficient calories, cortisol rises. For athletes in heavy training, that's a double hit. You're never fully recovering. Just accumulating the deficit.

The Performance Tax You Didn't Know You Were Paying

I was a product of the media on this one. For years I was flipping containers looking for the lowest fat number. Low-fat yogurt, reduced-fat everything. I thought I was doing it right.

What I couldn't figure out was why, despite training consistently, I was struggling to build muscle and my sessions felt flat.

What happens when fat is too low:

You burn through glycogen faster. Fat is your primary fuel at low-to-moderate intensities. Chronically low fat makes your body over-reliant on carbs. You fade in the back half of sessions.

Muscle building gets blunted. Fat is the substrate for testosterone. Cut it too low and you're asking your body to build tissue while rationing the materials.

Before you add more volume, check what your fat intake actually looks like across a week. Do not be afraid of fat mate, just make sure to be eating the foods containing ‘quality’ fat.

Fat and Recovery

Deliberately eating more quality fat is one of the most significant shifts I've made — and right now my lean muscle mass is the highest it's ever been.

Part of that is calorie density. Fat delivers 9 calories per gram versus 4 for protein and carbs. When you're training hard, it's the most efficient way to hit your energy needs without eating enormous volumes.

Why fat changed my recovery:

Inflammation control: Omega-3s regulate the inflammatory response after training. Without enough, you're sore longer, stiff longer, and the next session starts before the last one's closed. My output is hitting the strongest numbers I've ever seen — and a big part of that is my ability to back up sessions. Fat has been a real factor there.

Sleep quality: Testosterone and growth hormone — the hormones that actually rebuild you — depend on adequate fat. Low fat means you're getting the hours but not the depth.

The Fats Worth Prioritizing

In my opinion we need to stop framing “good fat vs bad fat.” It's which fats are doing active work, and which are filler.

Fats worth building your diet around:

• Fatty fish (salmon, sardines, mackerel)

• Extra virgin olive oil (daily, not just for cooking)

• Avocado and avocado oil

• Quality beef and eggs (grass-fed where you can)

• Walnuts and flaxseed

Target: 25–35% of daily calories from fat. In a heavy training block, lean toward the upper end.

Recipe: Epic Spicy Salmon Sheet Pan

Omega-3-packed salmon with a spicy marinade, roasted vegetables, and olive oil—quality fats that fight inflammation and fuel recovery.

RECIPE HERE →

Cals: ~480 · Fat: 32g · Protein: 38g · Carbs: 8g

Final Thoughts

Let me just repeat I was that person who avoided fat, but now I always look for the quality sources i need in my day. I spent years working against myself without knowing it. Eating quality fat intentionally is one of the highest-leverage changes I've made—and the results speak for themselves.

I can understand that the term 'quality' can be really broad. This is why we built Alma, as your nutrition coach, so can log your foods, it can tell you if you are hitting the right quality and provide you with information on what you specifically need. It is kind of like me on your pocket. So if you need a nutrition coach, use code ALMA 50 download Alma today for 50% off!

Eat quality fat. Eat enough of it.

Quick Notes

🏃Headed to Pittsburgh this week with BPN for the marathon — hope to see you legends out there!

🥣 Really cool to see so many Overnight oats being created from the recent video

🍏 New on Alma: you can now upload your blood work directly. Connect it with something like Hone and your nutrition coach gets a whole lot more personal. Know your deficiencies, fix them.

#EatGoodFeelGood

— DC