Do Calories Really Matter When It Comes to Weight Loss?

5 min read

We’re going to start this post off with a bit of a story…

Recently, we were made aware of a video doing the rounds on social media of a famous American/British scientist spouting out that calories do not matter when it comes to weight loss.

It was slick, it was sexy with lots of whooshy sounds, fancy captions and dramatic music, clearly created to hook people into watching the full 1:52:31 long video on YouTube and rile up the weight loss and/or the fitness community peeps.

Classic marketing ploy 101…

Watch the full video with Professor Giles Yeo Here!

In 30 seconds, we were bombarded with out of context statistics ranging from the ‘fact’ that “the average person” will gain 15 kilos between the ages of 20 and 50, that a 6 calorie stick of celery somehow becomes 30 calories when cooked and that veganism is a “diet for the privileged.”

We were even left on tenterhooks when the topic of juice was brought up…

Add to that an American voiceover the likes of which only the most epic of Hollywood blockbusters would receive, it’s pretty clear why this video has so many of the health and fitness community talking.

And we want to weigh in.

BUT, before we crack on, yes, we did, in fact, watch said video - all 1 hour 52 minutes and 31 seconds of it – paying very close attention to the sections titled How to Burn Fat, Calorie Counting, Does Exercise Help Us Lose Weight? And Juice is Bad!

If drama was the aim, Professor Giles Yeo certainly has game.

In just under 2 hours he not only promoted his book “Why Calories Don’t Count: How We Got The Science of Weight Loss Wrong,” but he made the whole idea of losing weight sound, well, downright confusing.

If you’ve ever tried to lose weight, you will undoubtedly have heard of the calories in vs calories out concept.

AKA the Calorie Deficit.

In short, this concept supports the idea that if you eat fewer calories than you burn each day, you will lose weight.  Simple, right?

However, Professor Yeo does not agree with this.  He believes that the quality of the food we eat is more important for weight loss rather than its caloric content, which is where it all gets just a bit murky…

Understanding Calories in, Calories out

Calories in = the energy you get from food.  Calories out = the energy you burn.

You mainly use these calories to fuel three main bodily processes:

1.      Basic Metabolism – this is your Basal Metabolic Rate (BMR) which is the amount of energy you use when at rest and your body gets cracking on with all its essential life functions like your heart beating, breathing, hormone production etc.

As you age, your BMR naturally reduces, however people who have more muscle tissue to adipose (fat) tissue tend to maintain a higher BMR than those with high body fat.

2.      Digestion – Ironically, you use approximately 10-15% of the calories you ingest to digest the food that gives you calories!

3.      Physical movement – Any energy that’s left after all of the above will be used to fuel physical activity and movement – and that means ALL physical movement, from simply typing at your computer to lifting weights in the gym.

In order to calculate just how many calories you ought to be eating on a daily basis to fuel these functions, you need to work out your Total Daily Energy Expenditure (TDEE).  

You can do this yourself, but it’s much easier to use a TDEE calculator which will work out all the sums taking into consideration your activity level, age and lifestyle.

Why does this matter for weight loss?

You can probably tell already that the whole calorie thing can be a bit of a rabbit’s warren – yeah?  So, we’ll keep this next bit short…

When you know your TDEE and just how many calories your body needs to be able to do essential life functions, it makes it a lot easier to determine just how many calories you need to be eating to lose weight.


Well, by eating fewer calories than your TDEE, you will put yourself into a calorie deficit and your body will then use up stored energy – glycogen, fat – to meet its needs, thus leading to weight loss.

In a nutshell, eat fewer calories than your body burns = weight loss.

However, this is where things become really quite murky for there are some, really rather biased, studies that “prove” that what you eat is more important for weight loss than how much you eat.

Take The Keto Diet and Atkins, for example.  Their low-carb ethos appears to help people lose weight faster whilst eating the same number of calories as someone eating a balanced diet, but what they fail to accurately indicate is just how much of that weight loss comes from loss of water and muscle tissue.

Not fat.

Professor Yeo appears to fall into this camp.

Not all calories are created equally

Yeo argues that not all calories are created equally, and he is correct. 82 calories gained from eating 200g of carrots has more nutritional value than 256 calories gained from eating 82g of French fries in terms of micronutrients.

In theory, you could eat fast food every day and still be in a calorie deficit and end up losing weight, yet your overall health would suffer as you likely wouldn’t be meeting your other nutritional needs.

In fact, the Twinkie Diet phenomena in America proved just that.

Foods that provide you with greater vitamins, minerals and other essentials – think fruit, vegetables, whole grain sources - will have a better impact on your overall health than highly processed foods with a low nutritional value.

Nutrient rich diets, like the Mediterranean Diet, are known to reduce an individual’s risk of developing chronic diseases and obesity.  This is certainly one area where the If It Fits Your Macros model fails to take into consideration.

Which is why, here at MuscleFood, we promote a healthy, balanced diet made up of lots of nutrient dense foods for a healthy body, healthy heart, healthy lifestyle.

You’re confused? We’re confused bro…

We could fall down that rabbit’s hole all day, but it gets really twisty when looking at the science and how hormones come into play, metabolism, hunger etc so…

Yeo is right, but he is also wrong.

Yes, nutrient density matters.  Foods rich in vitamins and minerals will inevitably have a better long-term impact on your body, mind and health.  Plus, eating these foods may actually make your journey to weight loss a little easier.

BUT, at the end of the day, if you want to lose weight for good, you simply must burn more than you eat, that is a simple, true fact.

And don’t get us started on his comment that exercise is only useful for athletes to lose weight… honestly, it’s, just biased thinking.

Calorie deficits work for lasting weight loss.  What’s your opinion?

If you’d like to start your journey to weight loss but not sure where to begin, we can help with our Goal Getters plans!  Check them out and kick start your journey to a healthier you.

Ashleigh Tosh

Ashleigh Tosh

Ashleigh is a Copywriter and content creator with over 10 years experience writing for the health & fitness industry. She's currently training for her first powerlifting comp at the end of 2023!