If you, like so many of my clients, have a goal of losing excess body fat, optimising energy levels and feeling your best self then calorie counting alone won't get you there. In this article I want to take a step back and explain the science of calories so that you can take a step forward and appreciate that they are not the 'be all and end all' of sound nutrition. In achieving a goal of losing excess body fat and optimising energy in actual fact your goal is teaching your body how to 'burn fat for fuel'.
What is a Calorie?
A calorie is a measure/unit of energy - the energy stored in the chemical bonds of food. It is defined as the amount of heat required at a pressure of one atmosphere to raise the temperature of one gram of water one degree Celsius. You may sometimes notice kilojoules being used as the measure of energy, in which case 1 calorie is equivalent to 4.19 kilojoules. Our metabolism is simply trying to capture the metabolisable energy within the food that we eat. More on metabolism to come.
Are all Calories Treated Equally?
Let's be clear, regardless of the calories' source, it's ultimately still just a calorie:
One gram of fat contains 9 calories
One gram of alcohol contains 7 calories
One gram of protein contains 4 calories
One gram of carbohydrate contains 4 calories
There are however differences in how the various sources of calories influence metabolism and hormones. This is where you need to pay attention, because there are a few key metabolic and hormonal differences to be aware of.
Protein has the highest thermic effect of food (TEF) of all calorie sources. TEF is the amount of energy required to extract calories from the food. In consuming 100g protein 20-30% of that energy will be expended simply trying to digest the protein. Meaning that eating protein contributes more to total daily energy expenditure (TDEE) in comparison to fats and carbohydrate.
Protein is also the most satiating macronutrient which means eating adequate amounts should help to fend off cravings for poorer quality food choices.
The non-fibre component of carbohydrate elicites a greater blood glucose response than fats and protein. When blood glucose is high the body responds with insulin. Insulin is a hormone and its' role is to keep blood glucose levels safe. In its' presence the body will prioritise the use of carbohydrate (glucose, stored as glycogen) as a fuel source and promote the storage of fat.
Food quality matters. High fibre, complex carbohydrates (e.g. potato with the skin on or legumes) will elicit less of a blood glucose response than highly processed carbohydrate sources (e.g. white bread, sweetened beverages and confectionary). Refer back to point 3.
The Flaws in Tracking Calories in Pursuit of Fat Burning
As you now know, the calorie's source alters hormones and metabolism - two key factors in supporting fat burning. A high carbohydrate, low fat and low protein diet will promote high insulin and fat storage. In contrast, a diet lower in carbohydrate and conversely higher in protein and fats will promote greater energy expenditure (through TEF), more opportunity for fat burning and less cravings.
There are also documented flaws in one's ability to track calorie intake and expenditure. Research shows that people are generally really bad at measuring and estimating how much they eat. The prevalence of underreporting in large nutritional surveys ranges from18 - 70%. So, you could eat to a calorie target and potentially overshoot that target by 18 - 70% or, eat to feel satisfied and nourished in turn giving your body what it actually needs. There also has to be allowanced for inaccuracies in the reported calorie content of foods - the FDA and other agencies have to allow for at least a 15 - 20% margin of error.
On the other side of the energy balance equation, the accuracy of energy expenditure (EE) predictions from wearable devices is incredibly poor. A 2017 study indicated that devices can produce error rates of between 23 - 93%, hardly making the figures worth tracking let-alone worth using as a means for justifying energy intake.
The truth when it comes to supporting fat burning ability is that it requires metabolic health and flexibility. Neither of which will be achieved by eating to a calorie value at the exception of all else. It requires strategy and lifestyle change. What's more, until metabolic health and flexibility are achieved long term fat loss can't be expected.
If you have found this insightful then you will love my upcoming Masterclass: Burn Fat For Fuel. Incorporating my undergraduate degree in Exercise Science and Nutrition, 14 years industry experience and 6 years clinical experience, I’ve written this Masterclass to help you understand how to lose and burn body fat safely, healthily and from a sound base of evidence. I share lots more detail on eating to support stress, inflammation, hormonal imbalance, and nutritional status. We’ll also look at the testing required to help you uncover the blind spots around your fat burning ability.
Will you join me? You can watch the Masterclass live on December 5th, 7.30pm AEDT or catch up via the recording.
Macdiarmid J, Blundell J. Assessing dietary intake: Who, what and why of under-reporting. Nutr Res Rev. 1998;11(2):231-253. DOI: 10.1079/NRR19980017
Nishino K, Sakurai M, Takeshita Y, Takamura T. Consuming Carbohydrates after Meat or Vegetables Lowers Postprandial Excursions of Glucose and Insulin in Nondiabetic Subjects. J Nutr Sci Vitaminol (Tokyo). 2018;64(5):316-320. DOI: 10.3390/jpm7020003