The 80:20 Rule – Is it really 80% diet, 20% exercise?

I get lots of clients ask me – which is more important – diet or exercise, and is it really 80% diet and 20% exercise?

Well, yes and no.

Essentially the 80:20 rule comes from the fact that in order to lose body fat you need to take in less calories than you burn.  Roughly 500 grams of body fat (1/2 kg) consists of 3,500 calories. So to lose 500 grams of body fat in a week you need to burn 500 calories each day beyond those calories you consume to keep your body functioning. So, if your daily number of calories you should consume based on your body composition is 2,000 calories, you need to burn 2,500 each day in order to lose body fat.

BUT, here’s the thing…

It not only takes a lot of effort to burn 500 calories in a workout (at least a 45 minute run, depending on your pace), but it is also really hard to eliminate 500 calories from your diet!

So instead, focusing on both a healthy diet and exercise is essential, which means you don’t have to make dramatic changes within both areas at all.  For example, you could eliminate 500 calories by burning 250 calories in a fitness class and then cut another 250 calories just by skipping your nightly bowl of ice cream.

And here’s another thing that I have spoken about before….

It’s not just about the calories you consume but the types of calories you consume or the macronutrients you eat (proteins, carbs and fats).  See my previous blog on this:

What the hell are Macros??

Many of us have told ourselves at one point or another when we have eaten or drank something unhealthy that “It’s okay, I’ll just do a massive workout session and burn it off.”  However, unfortunately, you cannot “out-exercise” your diet if what you have consumed is made up of higher saturated fats and simple, sugary carbohydrates which take longer for the body to break down and simply convert into body fat. 

So the point of all this is that we all need calories to survive and not eating enough calories can actually be detrimental to our fitness goals.  But, the food choices you make are definitely going to determine your weight, which is why a healthy diet is so important.

But, in my opinion, although a healthy diet is important, you don’t need to focus exactly on an 80:20 ratio to lose weight. Both diet and exercise are absolutely necessary for a strong, healthy, body.  This is because losing weight from diet alone is going to result in a frail body, lower immune system and higher risk of disease, as our bones and muscles deteriorate as we age if we don’t use them!   On the other hand, weight loss via diet and exercise is going to result in a significantly stronger, healthier body, and amongst other things, will strengthen your heart, bone density and immune system and ward off disease.

Therefore, the bottom line – both go hand in hand!  And not focusing on your diet the majority of the time is certainly going to undo any hard work that you may have put in during exercise!  You know how hard you work out when you do get to a class, so don’t let this hard work go by the wayside by making poor food choices!

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