The humble calorie, a measurement of the amount of heat energy required to raise the temperature of one gram of water by one degree Celsius, and the unit by which weight gain or loss is determined. Everybody is aware of it and the practice of calorie counting is employed the world over by those monitoring their weight, but just how accurate is it and ultimately does it help us control our weight?

Weight loss/gain is governed by what is known as energy balance, or simply put calories in verses calories out. If more calories are consumed than utilised then weight goes up as energy is stored in the body, with the reverse being true when calories out is higher than taken in whereby weight loss will occur. When put this way it makes the task of manipulating body weight seem easy, simply track calories in and out and adjust according to the desired outcome. If we ignore the myriad of other factors surrounding our food intake such as pleasure, social and availability influences, then this is indeed all that is required, but just how easy is it to do?

Let’s start with calculating our daily calorie intake. Assuming that we do not have access to expensive lab equipment, then our intake will be calculated using food labels and tracking devices such as MyFitnessPal and the like. A basic enough principle, simply write down everything that you eat and then add up the calories to give you your total daily intake. However, already we can see a number of issues present themselves at this early stage. First, this method assumes that we will in fact record everything that we consume, but with the best will in the world this is not always the case and unless we weigh everything, amounts will be purely estimated. Add to this the amount of mindless eating that we do (grabbing a biscuit as we pass the packet or that sweet taken from a work colleague), the liquid calories that are often neglected and the sauces, condiments and cooking oils used but not noted, and already we can see that this list may not be the most accurate. The labels on foods and listings on our nutrition apps cannot be precise for the food that we are eating since to say an apple contains 80 calories may represent an average, but cannot be accurate for each apple sold/consumed. The same goes for any foodstuff, since regardless of the level of processing, no two foods of the same type will contain the same number of calories. Then we have the cooking method which may affect calories and the combination of foods within a meal which will play a part in the rate and amount of absorption. The amount of nutrients absorbed is dependant on the individual’s general health and gut flora, and it must be remembered that we eat meals, not individual foods and this, along with how it is prepared will result in different levels of absorption and speed of transit through the digestive system.

So much for accurately tracking what we consume!

Then onto the other side of the energy balance equation, energy (or calories) out. Again, without expensive techniques, this is nigh on impossible to gauge with any level of accuracy and so is more often than not calculated using mathematical formula or the activity trackers which are now so common. Calculations such as the Harris-Benedict method take the BMR (Basal Metabolic Rate) and multiply this by a factor denoting a persons’ activity level to give an idea of daily energy expenditure, with the activity classed as light, moderate, heavy, etc and so this in itself is very subjective and open to misinterpretation; most people overestimate the effort they are putting in. What one person may class as heavy, another may deem moderate and hence this multiplying factor can be very inaccurate. So perhaps the activity trackers are a better method, but again, problems present themselves using this technique. If we gloss over the general inaccuracy of these devices (a heart strap will give a more accurate reading than one worn on the wrist), the use of heart rate to assess energy utilisation is in itself flawed unless steady state exercise is undertaken as many activities such as lifting weights include many instances when no work is being undertaken whist heart rate is still high, hence giving a false high reading.

So, should we bother tracking our calories or are we just wasting our time due to the factors listed? Whilst it can be useful to keep an eye on our calorie balance, the inaccuracies of the methods we can use make this difficult to do with any level of precision, so the answer may be just to be more aware of our input/output and make adjustments depending on how our bodies react. Trackers are great for recording our diet and exercise, can be incredibly motivational and so are definitely worthwhile for those looking to monitor their daily behaviours, but please don’t rely on their data as anything more than a method for adjusting intake and giving a rough idea of calories consumed. Enjoy your food, consume a varied diet and adjust calories dependant on your goals, but be aware that calorie counting is not an exact science when undertaken outside of laboratory conditions. Tracking food and activity rather than actual calories may prove to be an easier overall method, and although it is important to be aware of which foods are high or low in calories this generalisation can be more beneficial than the exact figures involved. Don’t fear calories, they provide the energy we need to survive after all, but be aware of how they effect your body composition and that the methods we use to track them on a daily basis lack any true accuracy.

Stay fit, healthy and happy!


I am a fully qualified Personal Trainer with over 22 years’ experience. Find out more about my specific training and qualifications or book a personal training session.

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