Diet or exercise: which matters more?

On the internet, from clients and in the media, I keep hearing the same thing: "diet is 80% of success, training is 20%!" Or the other way: "training is 70% and diet 30%!" Let's look at what training and food actually do to your body. Maybe one day I will live to see these myths die. They come from not understanding how the body works.

Short answer: Both matter the same. Only together do they move you forward physically, and one without the other does not work. Training gives the body the signal to build muscle. Food gives it the energy and nutrients to rebuild that muscle. If you forced me to pick one for muscle growth alone, training would win.

What training does

Training, if it is set up and done properly, tells the body it has to adapt to new conditions. It has to get ready for the next load so it handles it better, or without trouble.

Very simply, this is a signal for the body to invest a lot of energy into muscle protein synthesis: building muscle, plus the energy that process costs. Without the stimulus from training, the body has no reason to waste that energy.

Strength training has one more upside on top of giving the body a reason to make muscles bigger and stronger. It burns energy: on the muscle work during the session, and on the muscle protein synthesis afterwards. That process is very expensive in energy. So you need enough macro and micronutrients in your food to pay for it. Keeping that muscle while you diet is in build muscle in a calorie deficit.

What food does

Your food affects hormones, the managers of the human body. They run muscle protein synthesis, fat loss, health, how you feel, hunger and more.

Food also gives the body energy, macro and micronutrients, so the muscles have something to rebuild from and grow with. Always tied to the stimulus from training, though.

Food always balances out training and stress.

Training, on the other hand, can offset a higher food intake. The food then gets used instead of being stored as fat. I am simplifying a lot here, of course.

So even if you train, your muscles will not grow if you do not eat properly. They will have nothing to grow from. Protein is the first place to start: how much protein you need.

So which is "more" important?

Neither is more or less important. They are equally important, and only together do they let you move forward physically (or go backwards). One without the other does not work. Yin and yang.

If I had to be really strict about what matters "more" for muscle growth, I would say training. Train hard enough and your muscles will grow even without perfect food, just not optimally. Eat perfectly but skip training, and your muscles will not grow.

But the same goes the other way. If you ate truly nothing, which is the fair comparison to "not training at all", you would not get far either.

Frequently asked questions

Will my muscles grow if I train but do not eat well?

If you train hard enough, your muscles will grow even without perfect food, just not optimally. But if you do not eat properly, they will have nothing to grow from.

Will my muscles grow from good food alone, without training?

No. Eat perfectly but skip training and your muscles will not grow. Training is the signal that gives the body a reason to invest energy into building muscle.

What exactly does food do for your body?

It affects the hormones that run muscle protein synthesis, fat loss, health, how you feel and hunger. It gives you energy, macro and micronutrients so the muscles have something to rebuild from, and it balances out training and stress.

Sources, so you can check:

1) The article cites no studies. It explains the roles of training (the signal for muscle protein synthesis) and food (energy, macro and micronutrients, hormones) in plain terms.

Martin Barna

Online nutrition and fitness coach. Since 2013 I have helped 600+ people lose fat and keep the result. Science, not crash diets.

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This article is for information only. It is not medical advice. If you have a health condition, talk to your doctor.