Fat Burning: The Cold, Hard Truth

Fat burning. Whether you're trying to shift a few pounds or you're a lean racing snake chasing performance, this is where science, food, and training all collide.

And after 30 years of writing, coaching, and answering the question ‘How do I burn fat?’, I’ll give it to you straight.

If you remember just one thing from this article, let it be this:

Eating a low-fat diet and training too hard = less fat burning, more fat gain.

I know, shock horror. We’ve been sold “low-fat” everything. Supermarkets have made it look healthy. You’ve heard elite athletes eat bucketloads of carbs, so that must be the way to lose fat, too, right? And of course, no pain, no gain. Well, wrong. On all counts.

Let’s get stuck into what actually works.

1. Fat is your friend: Eat at least 1/3 of your calories from quality fats

Essential Fatty Acids (EFAs) are called essential for a reason. You need good fats to fuel your body, support hormone function, and fire up your metabolism.

Back in 2003, a group of scientists conducted a study^[1]. They gave one group of athletes a high-fat diet (60% of calories from fat) and another group a low-fat diet (22% of calories from fat). After just two days, the high-fat group were burning 70% more fat during exercise. The low-fat group? Their bodies were burning through carbs instead.

Other studies have shown that fit runners put on a lower-fat diet reduced their fitness and endurance^[2], and it has been suggested that very low-fat diets could “compromise health and performance”^[3].

Low-fat diets don’t just reduce fat burning, they can blunt endurance and compromise performance. I’ve seen triathletes spending thousands on bikes, tech, and supplements, only to discover their data shows they are very, very poor fat burners

Lesson: Ditch the supermarket “low-fat” nonsense and start eating like someone who wants to burn fat, not store it.

2. Exercise easy and often: Long is where fat burning lives

Fat is a slow-burning fuel. It doesn’t jump in straight away, so short, hard sessions don’t tap into it much.

You’re burning around 60 calories per hour just reading this. Go for an easy jog and you’ll burn 400–800 (that’s about 100-190 watts, respectively, for your cyclists).

That’s a 6–12x increase. The trick? Keep it easy. Nose breathing is a good guide. If you’re puffing and panting, you’re into carb-burning territory.

Sure, intensity has its place, but if fat burning is the goal, then steady-state, longer duration sessions (think 90 minutes to 2+ hours) are gold dust. No need to cane yourself. Just get out regularly, enjoy it, and go long when you can.

Reality check: That 45-minute “fat-burning” spin class? You might burn 15–20 grams of fat, tops. Most of it’s sweat and noise.

3. Lift heavy: Resistance training is your secret weapon

Want to burn more fat at rest? Then build some muscle. Muscle is metabolically active, it burns more calories just sitting there than fat ever will.

You must make hard strength training a weekly habit. But let’s be clear: we’re not talking about endless sets of 15 reps with lightweight dumbbells. You need proper resistance. Pick a weight that challenges you for 8-10 reps.

If you can do more, go heavier. Train hard, rest well, and don’t follow cardio with more cardio.

It’s simple: muscle = engine. Fat = fuel. Build the engine, and it burns more fuel.

Bonus: You won’t bulk up unless you try really, really hard. You will get functionally stronger, leaner, and more resilient.

4. Manage carbs: Match your carb intake to your training and prioritise protein

Think of your diet as the building blocks for tomorrow’s body. Quality in = quality out.

For most people, the sweet spot is something like 30% fats, 40% carbs (from proper foods, not sugar bombs), and 30% protein. That gives you good fuel, good repair, and stable energy.

Yes, endurance athletes training 10+ hours a week might need more carbs, sometimes a lot more. I’ve coached riders who take in 1,200 calories during a 3-hour bike ride.

Some elite athlete data shows they can consume over 1kg (yes, 1000g) of carbohydrate per day during heavy training^[4], which breaks the dietary government guidelines for the populous but elites (or super keen amateurs doing over 10 hours rigorous training) need premium fuel and a lot of it.

But if you’re exercising under an hour a day and still smashing high-carb snacks and low-fat meals, you’re just keeping yourself on the fat-storage hamster wheel.

Top tip: Check out the glycaemic index. Apples = good. Mars bars = not so good. Couscous sits somewhere in the middle. Simple swaps, big impact.

5. Want to burn more fat? Here's your cheat sheet:

• Go slow

  If you’re mouth-breathing, you’re going too hard. Dial it back.

• Go long

  Save time for a proper hike, bike ride or long swim session.

• Train fasted (occasionally)

  Morning sessions before breakfast can help. Just don’t overdo it.

• Calm down

  You’re not in a race. Cruise at your pace. Don’t compete with the person next to you in the gym.

• Lift weights

  Strength training changes your body, metabolism, and long-term health.

• Avoid unnecessary products

  If you train less than 6 hours a week, you don’t need recovery shakes, pre-workout drinks and post-cardio bars. Fruit and water are fine.

6. How to sabotage your fat burning (a checklist to avoid)

1. Believing low-fat means healthy

2. Doing short, intense cardio, inconsistently

3. Falling for “all-in-one” trendy drinks

4. Skipping strength training for "toning"

5. Avoiding good fats because they’re high calorie

6. Letting food choices be dictated by convenience

7. Believing the hype, not the science

So, What’s the Real Fat-Burning Formula?

There’s no magic food, no perfect workout class, no overpriced protein bar that melts fat off your body. It’s about:

• Eating real food with good fats, steady carbs, and enough protein

• Moving regularly, especially steady, longer efforts

• Lifting heavy things once or twice a week

• Staying consistent, being patient, and not falling for quick fixes

That’s how you become a better fat burner. That’s how you shift stubborn weight. And more importantly, that’s how you build a body that works with you, not against you.

Final word: Be a Cynic

There are hundreds of products designed to keep you stuck – stuck craving sugar, stuck in cycles of weight gain, stuck believing the next trend is the solution. Don’t buy into it.

You are what you eat, drink, and do. Take ownership, question the hype, and trust what works.

Joe Beer has been in endurance sport since the 1980s — from 10Ks and Ironmans to ultra runs and London to Paris charity cycles. He’s coached thousands of athletes (from newbies to elites), written for national magazines, published books, and regularly shares straight-talking advice on his podcast.

He lives the lifestyle: aerobic training, strength work, and the occasional competition — always learning, always testing, always helping others do better.