Do Calories Matter?

January 26, 2018
Lucy Mecklenburgh

Calories are an important issue to consider with weight loss.  There we said it!  It may be fashionable to endorse certain nutritional philosophies that explain you only need to eat in a certain time frame, or a specific macronutrient split, but it’s undeniable that when it comes to losing weight, THE most important consideration is energy balance - how many calories your body takes in compared to how many it expends.  

As it is our normal human behaviour to make things very black and white or simplistic, the idea of calories being so important often gets attacked because people see this an a license to simply eat rubbish foods all day, but as long as you are in a calorie deficit they will lose weight.

Well, in some respects this is actually true.  Professor of Nutrition, Mark Haub, famously ate a junk diet known as “The Twinkie Diet” for 10 weeks.  He created a caloric deficit but only ate overly processed, sugary junk food for 10 weeks.  His results and diet plan you can read about here.

He lost 27 pounds in two months, his Body Mass Index (BMI) went from 28.8 (overweight) to 24.9 (normal).  His LDL (so called bad) cholesterol dropped by 20%, his HDL (so called good) cholesterol increased by 20%, his triglycerides dropped by 39% and his body fat dropped from 33.4 to 24.9 %.

So clearly calories matter in terms of weight loss and the real secret of success behind all diets is they create a calorie deficit.

Large obesity reports from the OECD  and the World Health organisation show that obesity is rising in every country in the world, and this is despite many countries actually eating a lot less sugar, and less fat. The issue is they are eating a lot more of everything! The key issue worldwide is that people everywhere are eating more, this combined with a less active lifestyle equals a worldwide calorie excess.  

So calories matter with weight loss, however as always it’s not quite so simple.

Firstly, working out how many calories you need to lose weight is not a definite science.  There are multiple online calorie calculators that do this for you, and we provide you with one within our 'Fitness, Food and Mindset Membership'  and 'EatWell with Lucy' programmes but please be very clear that these are always estimations, and should only ever be used as a guideline.   

Working out how many calories you are consuming is also extremely difficult and time consuming.  Calories are often printed on a packet, but the assimilation of these calories can vary from person to person.  How many calories you need to eat to lose weight, and how many calories you are actually taking in are difficult to ascertain, and even if you put all that effort to do so, it’s still ultimately just a guideline to work from, a useful guideline but one that must be flexible for you to adapt with trial and error.

We’ve made life as simple for you as possible for you with calorie estimations of our meals and daily/weekly calorie guidelines, but you must always adjust dependent on your personal results.    

The next step is creating a nutritional plan that is realistic and something you can be consistent with.  As alluded to above, the most successful determinant of whether someone loses weight or not, is not the diet they are on but whether they can comply with the diet! 

Janda explains that adherence to behavioral weight loss strategies is the most important factor for weight loss.  This is the CRITICAL part to understand in weight management because you will see people who’ve had great results on a Ketogenic Diet (which is extremely low carb) and you’ll see people who have had great results on a high carb low fat diet, and you’ll see people who’ve had great results with every diet in between from Intermittent Fasting, Paleo, Vegetarian etc etc.         

From the information above you could realistically eat three Mars Bars a day and lose weight.  Hooray 👍 you say, well maybe not so fast.  Yes, technically this could happen but remember the most important factor in any weight loss program is compliance.  This is a very simple phrase but has enormous complexity. So to state the obvious if you only ate Mars Bars for one month you’d likely become very ill, and have a range of nutrient deficiencies, it would very quickly become impossible to sustain, however you could almost say this about any food, just only eat kale for a month and you will likely run into problems with inadequate nutrition.

Here at RwL we understand that losing weight is a healthy intervention for many people with a large amount of benefits but we must also ensure the weight loss is as healthy as possible and doesn’t actually cause health problems down the line.

Your body needs a certain amount of calories to function, there are so many biological processes ongoing constantly within your body that we are not even aware of.  All of this normal functioning requires energy.  So to stay alive we need a certain amount of calories, if this is too low we can health problems, commonly nutrient deficiencies.  This is why the Mars Bar diet is not a good idea long term.

A healthy diet is simply a combination of a variety of nutrients and minerals.  The good news is you can live a long and healthy life on all of the diets mentioned above, whether you are vegan, vegetarian....whatever.  There is plenty of room within all to ensure you can live a healthy life.

Satiety is also a HUGE factor when it comes to the success and compliance of a weight loss programme.  For most people on a weight loss journey, they will be lowering there calorie intake and eating less foods overall.  It doesn’t take a rocket scientist to realise that a consequence of this is that people will get hungrier.  In a modern environment with lots of highly palatable, and high reward foods, when you are hungry, a dominant part of your brain, which PhD Stephen Guyenet refers to as your “chimp brain”  (which enjoys instant gratification and doesn’t worry about the future) will make it very difficult for a hungry person to resist foods. 


To Sum It Up....

  • Calories are important in a weight loss program

  • The most important factor in a weight loss program is compliance

  • It’s important to ensure we are still getting adequate nutrition into our bodies, which can be done in a variety of ways.

  • Satiety is important in weight loss


    The calorie balance is right at the heart of weight loss but the enormous factors that influence it are exhausting. This is why here at RwL we encourage a flexible approach to your dieting. The right diet for you is the one that you will follow. What you can follow easily may be impossible for someone else to comply too. We’ve created diet plans from a variety of common diets, ensuring that they are nutrient packed so you can work out which way of eating is best for you.

    You will need to get an idea of how many calories you should be eating, and adjust monthly based on your results.  If you hate low fat foods, then going on a low fat diet is unlikely to be for you, likewise if you cannot resist meat, then a vegetarian diet is probably not sustainable for you, but going veggie for a few days, all kept within your caloric guidelines, is perfectly fine. 

    In theory you could follow a vegan diet on a Monday, intermittent fasting on a Tuesday, vegetarian on a Wednesday, Mediterranean on a Thursday.

    It’s completely all about you, what your preference is, what you can comply too, what you feel good eating and least hungry on.  


    👉🏽 Click here to start your 7 Day free trial and to access more nutritional advice! 👈🏽

    Lucy Mecklenburgh
    Found & Fitness Guru

    Lucy founded Results with Lucy to help ladies transform their health & lives. 

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    • Hannah September 17, 2019

      I have learnt so much about the importance of calories since starting RwL, but in a really non-obsessive way :)

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