Why the calorie equation doesn't work

When I was studying nutrition, we were told to use the following formula for weight loss, which you may recognise as the “Calorie Equation”.

How it works:

Step 1: Work out your BMR (Basal metabolic rate) using the Harris Benedict Equation

Step 2: Multiply this by an activity factor – for example 1.2 for sedentary, 1.6 for moderate activity, etc. to get your total daily energy expenditure.

Step 3: Set a deficit, e.g., for 1kg weight loss/week, currently recommendations are to reduce calories by 500cal/per day.

Step 4: Set the macro nutrients – current mainstream recommendations are: 45-65% carbs, 15-25% protein, 20-35% fat. (Higher carb, low protein, lower fat)

The end.

However, I realised there was something wrong about this equation during my trialthlon and body building days. For 5 years I was training 3-4 hours a day, eating litter over 1200 calories, just to maintain my weight and I constantly felt like I was “hanging in there”.

I then did the opposite to enter a body building competition and was eventually being able to consume 2000 calories doing zero cardio and losing body fat. According to the BMR equation, this shouldn’t have been possible. And that was a big wake up call for me.

Ever since this experience I have been passionate about answering the question -how can the calorie equation be so wrong?

I’ve learned through my own personal experience, research and working with clients over the last few years that we are much more complexed than an equation.

In this post I want to share with you 5 key factors that effect the accuracy of the calorie equation, to hopefully bring to light why you, or someone else you know may not be getting results on calorie counting alone.

1. Physiological adaptations to exercise

Adaptions to strength training (Lean mass) – The higher your lean mass is, the greater your BMR is likely to be. This is why I am a big promoter of incorporating some strength based exercise session into your week. A greater lean mass also improves your carbohydrate tolerance and insulin sensitivity (i.e. you can eat more carbs)

Adaptions to cadio training- When it comes to endurance training such as running/cycling/swimming, you get more efficient the more you exercise. For example, you can run the same distance and burn LESS calories. If you start doing ALOT of this type of training, your resting metabolism will also decrease as your body tried to reserve energy.

This can be good and bad….Good if you are an athlete and trying to optimise performance. But not so good if you are relying on cadio for weight loss. Bottom line here is, DO NOT rely on cadio for weight loss. I fell into this trap with triathlon training, and trust me, not even with 4 hours of training did i get to a happy place with me body. Quite the opposite.

2. Physiological adaptations to diet

To a point, when your calorie intake increases or decreases, your metabolism increases or decreases with it. This is a homeostatic mechanism your body has to help you to maintain a stable body weight long term (yes, your body wants you to stay the same weight).

The good news, is that you can use this to your advantage and build your metabolism up by increasing your intake (carbohydrates in particular), which then makes weight loss/maintenance easier long term.

The bad news, is that if you keep restricting your intake, your basal metabolic rate will continue to decrease, making it A LOT harder to lose weight/maintain long term.

3. Hormone imbalances:

Thyroid function – If you have developed an over or under-active thyroid due to things like stress, nutrient deficiencies (carbs, iodine, selenium), and over exercising, this will increase or decrease your resting energy expenditure. Those with an under-active thyroid often find it difficult to lose weight.

Liver function – your liver recycles hormones such as estrogen (key fat storage hormone) and is your energy production site. If your liver is being loaded with too much alcohol, processed foods, caffeine to name a few, this can impair your energy metabolism, estrogen recycling and hence, the ability to break down body fat. (Look after your liver!)

HPA Axis – Stress hormones can put a total halt on fat loss, regardless of your calorie intake. When you are stressed, your body starts using glucose instead of fat stores as its main fuel source. In other words, it down regulates fat metabolism.

4. Gut composition – The type of bacteria in your gut can affect the amount of energy you can extract from food as well as insulin sensitivity. Some recent studies have shown that the gut of an over weight individual yields more short chain fatty acids from indigestible food, which can then be stored as fat if not used by the gut cells.

5. A calorie is not a calorie – Researchers have come up with an estimate that: 1g of carbohydrate = 4calories, 1g Protein =4 calories, and 1g Fat = 9 calories. But these values are not set in concrete. It is important to understand that: A. These values have been rounded – 1g of carbohydrate can be anything from ~3.8-4.3 calories per gram. B. Depending on the source of the calories, there is going to be a different caloric effect on the body. For example… Some foods require more energy from the body to be broken down such as protein and fibre.

So in summary,

Based on this range of factors, you have the potential to provide a very inaccurate estimate of your true daily energy needs. I WISH I had this knowledge back when I was triathlon training. It would of given me so much more piece of mind to know that I wasn’t broken, I was just working against my biology instead of with it.

But on the other hand, by going through this myself it has enabled me to understand and help a lot of clients with the similar issues. And that has been incredibly rewarding. Its not just about the weight loss, its also HOW you get there.

So I hope this helps you understand a bit more about your body, and why a calorie restricted plan may have stopped working for you.

If you need help with exploring any of these issues, please don’t hesitate to make contact.

Kim xx