With regard to both the need for recovery and the optimisation of body composition, it is necessary to know not only how much energy the body consumes during training, but also how much energy it consumes independently of it. More specifically, with regard to recovery, knowing one’s energy expenditure is essential in order to best plan the optimal dietary strategy to replenish reserves; with regard to body composition, on the other hand, nutrition provides the body with energy such that, when related in its quantity to energy requirements, it can generate a mutation in body composition in one particular direction rather than another. Moreover, most people are familiar with the maxim (which, as we shall see, is not always true) that the more you eat, the fatter you get and vice versa.
Hints of bioenergetics
As is well known, the human body needs energy to stay alive. This energy is measured in calories, also called kilocalories (kcal). The body needs them for various purposes:
- basal metabolism: these are all those chemical reactions that the body must constantly carry out for the sole purpose of staying alive. These reactions serve to keep the heart beating, to allow lung respiration, or to perform more subtle, less obvious, but nevertheless equally important tasks for survival (e.g. cell respiration). Between 60 and 75 per cent of the total energy available to the body is used for basal metabolism.
- Physical activity: this refers to all voluntary movements one makes, from moving a pen over a piece of paper to sign a signature, to typing on a computer keyboard, to carrying shopping bags, to lifting barbells and dumbbells at the gym. Between 15 and 30 per cent of available energy is consumed in physical activity.
- Diet-induced thermogenesis (DIT): the simple act of eating leads to burning energy. A part of the energy that is acquired from food is in fact spent by the body on digestion, absorption and assimilation of food (i.e. by those processes whereby food is ‘broken down’, released into the bloodstream and incorporated into the cells).
- Maintaining particular physiological states: the most classic example of a particular physiological state is pregnancy. A pregnant woman, in fact, must feed not only to nourish herself, but also to nourish the foetus. The energy requirements of pregnant women, therefore, all other things being equal, are greater than those of those who are not pregnant.
- Thermogenesis induced by other causes: there are special situations that can increase cellular metabolic activity. One example is the intake of certain substances, such as caffeine.
The energy the body needs to perform these tasks, of course, comes from the food consumed. Each food contains a particular amount of calories. By manipulating diet (and exercise), it is possible to influence the body’s energy balance.
The importance of basal caloric intake and how to measure it
Some nutrition gurus claim that you don’t need to count calories and that what really counts to be successful in a body composition optimisation programme, as far as nutrition is concerned, is the quality of the food you eat. As for me, I firmly believe that, when it comes to nutrition for athletic purposes or, more generally, healthy eating, the quality of food is more important than the quantity, but this does not mean that calories count for nothing. This precept seems to be an extreme of the idea that quality comes before quantity. If thermodynamics is not an opinion, indeed, calories certainly count. Establishing an individual’s actual calorie requirements, however, is no mean feat.
The food diary
The technique that I find most effective in identifying one’s calorie requirements is that of the food diary. It involves, quite simply, keeping a note for at least a week of everything you eat and the exact quantity of each food, without neglecting any of the ingredients that make up your recipes (I recommend paying particular attention to seasonings. There is often a mistaken tendency to overlook them). Adding up the total calories of each meal (indicated, usually, on the food packages per 100g of them or, in the case of products not wrapped by the manufacturer, on the Internet) and calculating a daily arithmetic average will give the average amount of calories consumed daily during the observation period. It is necessary to take your body weight both immediately before and immediately after this time and, if this has remained unchanged, the amount of calories consumed is equal to your requirements. Otherwise, if the weight has decreased, it means that the calories consumed are less than the body needs, and if it has increased, they are in excess. If the weight has not remained the same (small changes, in the order of a couple of hundred grams are not relevant), then you will have to try to change something, proceeding by trial and error until you have found the optimal amount (possibly without varying the food you have consumed previously) of calories to introduce to keep your body weight constant. Let’s look at an example: let’s assume, for simplicity’s sake, that Mario Rossi consumes only three foods over the course of a week. Let us then assume that these foods have the following calorie content:
- food A: 150kcal per 100g
- food B: 300kcal per 100g
- food C: 500kcal per 100g
Suppose that in the space of a week, he consumed:
- 5300g of food A
- 1805g of food B
- 825g of food C
Now, to calculate how many calories you have introduced with your food, start by dividing by 100 the amount of calories that 100g of each food provides. This will give you the amount of calories that 1g of food provides:
- food A = 150 : 100 = 1.5kcal/g
- food B = 300 : 100 = 3kcal/g
- food C = 500 : 100 = 5kcal/g
Then multiply the result of the above operation by the amount of food introduced. This will give the amount of calories supplied during the observation period for each food:
- food A = 1.5 × 5300 = 7950kcal
- food B = 3 × 1805 = 5415kcal
- food C = 5 × 825 = 4125kcal
Now you have to add up the calories contributed by each food:
Total calories = 7950 + 5415 + 4125
Total calories ≈ 17500
Finally, one must divide the total calories consumed during the observation period by the number of days it consists of. The result will be the average calorie content consumed over the course of a day:
Average daily calories = 17500 : 7
Average daily calories = 2500
If, at the end of the observation period, an increase in weight is found, Mario Rossi must carry out a new observation interval of the same duration as the one just ended, always consuming, as far as possible, only foods A, B and C, but in smaller quantities. If, on the other hand, he finds a reduction in weight, he will have to consume more. Finally, if, as is to be hoped, he does not notice any appreciable change in body weight, then the average daily calorie intake identified is that equal to his requirements.
Estimates
If you find it difficult to use the food diary method, perhaps because you are aware that the calorie intake to which you are accustomed is quite different from your actual needs, you can resort to estimates. There are various mathematical formulae that take into account a variety of anthropometric (body) measurements that can provide an estimate of calorie requirements. Most of them are quite reliable, so much so that they provide similar indications, but, and this is something to always bear in mind, they are still estimates. And while I believe it is not possible to get a precise and truthful idea of an individual’s real calorie requirements even with the food diary method, this is particularly true when it comes to estimates. On the other hand, estimates, when they are well done, are also very useful. Below, therefore, are some ways of estimating calorie requirements.
Estimation of calorie requirements relative to basal metabolism
We have seen that the body needs calories for various purposes. The calories needed for DIT and cause-induced thermogenesis (previously referred to as ‘other causes’) can be considered negligible for our purposes. I also take it for granted that the reader is not a pregnant woman (otherwise, some dietary indications given in this work may not be valid). That leaves, then, the calories due to basal metabolism and those due to physical activity. Now, of the two, those related to basal metabolism can be estimated more reliably. We will therefore now show two mathematical formulae by means of which it is possible to estimate calorie requirements relative to basal metabolism alone (to which, then, those relative to physical activity must be added).
The Katch and McArdle equation
In order to calculate the caloric requirement relative to basal metabolism with this formula, we need the amount of lean mass, expressed in kilograms and easily deduced by having available information on body weight and the percentage of fat mass (which can be obtained as seen above). Before proceeding with the calculation of calorie requirements relative to basal metabolism, therefore, the weight of lean mass must be calculated. First calculate the weight of fat mass as follows:
FM = Fat mass percentage × Body weight in kilograms : 100
FM stands for Fat Mass, in this case expressed in kilos. The value obtained from this calculation must then be subtracted from the body weight:
FFM = Body Weight – Fat Mass Weight (kg)
FFM stands for Fat Free Mass, also expressed in kilograms. The result of this operation is the weight, in kilograms, of the lean mass. For example, suppose you want to calculate the weight of the lean mass of an athlete weighing 70 kilograms, with a fat mass of 12%:
FM = 12 × 70 : 100
FM = 8.4kg
8.4 kg is the total weight of body fat. Then proceed to calculate the lean mass:
FFM = 70 – 8.4
FFM = 61.6kg
61.6kg is the total weight of his lean mass.
Once the weight of the lean mass has been obtained, the calorie requirements relative to the basal metabolism can be calculated using the Katch and McArdle formula:
Basal metabolism requirement = 370 + 21.6 × Amount of lean mass (kg)
Continuing with the example from before, the calorie requirement relative to basal metabolism is:
Basal metabolism requirement = 370 + 21.6 × 61.6
Basal metabolism requirement ≈ 1700kcal
The calorie requirement relative to the basal metabolism of the analysed athlete is 1700kcal.
The Mifflin equation
An alternative method for estimating calorie requirements related solely to basal metabolism is the Mifflin equation. The parameters to be entered are:
- body weight;
- stature;
- age.
The equation differs according to the sex of the athlete. For women:
Requirement = 161 + 10 × Body weight (kg) + 6.25 × Height (cm) – 5 × Age (years)
Example: Assume you want to estimate the calorie requirements relative to the basal metabolism of a 30-year-old woman, 165 cm tall and weighing 64 kg.
Basal metabolism requirement = 161 + 10 × 64 + 6.25 × 165 – 5 × 30
Basal metabolism requirement = 161 + 640 + 1031 – 150
Basal metabolism requirement = 1682kcal
The calorie requirement to maintain the basal metabolism is 1682kcal. For men, on the other hand, the formula to be used, which is very similar to the previous one, is as follows:
Needs = 5 + 10 × Body weight (kg) + 6.25 × Height (cm) – 5 × Age (years)
Let us see the same example as before, assuming, however, that the data entered in the formula refer to a man instead of a woman:
Basal metabolism requirement = 5 + 10 × 64 + 6.25 × 165 – 5 × 30
Basal metabolism requirement = 1526kcal
The two methods compared
Personally, I consider the first method (Katch and McArdle) to be more reliable than the second, since it is also based on the percentage of lean mass, which is in itself indicative of age and sex. The second, however, has in its favour the greater immediacy of calculation and the need for more usual anthropometric data to be collected. Consider also the hypothesis of calculating calorie requirements relative to basal metabolism with both methods and then making an arithmetical average of the two results.
The level of physical activity (PAL)
We have seen that while the calories required for basal metabolism are relatively easy to estimate effectively, it may be rather difficult to obtain a true estimate of the calories required for physical activity. This is particularly true for athletes practising disciplines with varying metabolic demands, where some training sessions require a very different calorie expenditure than other sessions. A method will be proposed here to obtain as accurate an estimate as possible of the calorie requirements from physical activity.
The Schofield method
In reality, the amount of calories required for physical activity will not be estimated directly here. Instead, coefficients will be identified, depending on the work done, the type of sport practised and the frequency with which it is practised, which, when multiplied with the calories needed for the basal metabolism, will give a measure of the overall calorie requirement. Together, these parameters are called PAL (Physical Activity Level). Schofield proposes the following levels of physical activity:
- very light: people who have a very light PAL do sedentary work. They spend most of their time sitting in front of a desk or in a car and do not engage in any sports that require a caloric surplus;
- light: when Schofield thought of this PAL, he had in mind the lifestyle of the average student, i.e. the one who spends most of his time sitting and studying, but who walks or cycles, perhaps to class, once or twice a day. This ‘average student’, for Schofield, also plays some sport, albeit very lightly and no more than once or twice a week;
- moderate: those with moderate PAL participate in sports on average about three times a week or walk for several hours every day;
- heavy: heavy PAL is typical of those who engage in physically demanding sports for at least six hours a week, perhaps with competitive ambitions, but at an amateur level;
- very heavy: Very heavy PAL is typical of professional athletes who train several hours every day and of those who perform physically demanding work (e.g. labourer).
Now, since these are qualitative assessments, they can only be decidedly less rigorous and some people may find it difficult to choose the PAL that best suits their condition. One suggestion to reduce the awkwardness of such a condition a little would be to consider mostly metabolically demanding workouts (endurance training), ignoring pure technique workouts altogether, and taking little account of high-intensity workouts (strength, power and speed). For example, if you do mostly metabolically undemanding technical training and add two jogging sessions per week, each lasting 30 minutes, you can consider your PAL as ‘light’. If, on the other hand, instead of the technical sessions one does weightlifting for strength (e.g. in the style of powerlifting), then one can attribute one’s PAL as ‘moderate’. As far as ‘heavy’ and ‘very heavy’ PALs are concerned, I believe that these are only to be reserved for athletes (and workers) who have to carry a decidedly high metabolic load, such as amateur long-distance runners, professional long-distance runners (to whom I would attribute a ‘heavy’ PAL) or professional cross-country skiers (a ‘very heavy’ PAL). As already mentioned, Schofield associates a numerical coefficient with each of these PALs:
| Sex | PAL | Coefficient |
| Men | Lightweight | 1,3 |
| Lightweight | 1,6 | |
| Moderate | 1,7 | |
| Heavy | 2,1 | |
| Very heavy | 2,4 | |
| Women | Lightweight | 1,3 |
| Lightweight | 1,5 | |
| Moderate | 1,6 | |
| Heavy | 1,9 | |
| Very heavy | 2,2 |
How to calculate total calorie requirements
As already mentioned, once you have found the numerical coefficient that you consider most suitable for you, all you have to do is multiply it by the previously estimated basal metabolism requirement and you will have an estimate of your overall calorie requirement:
Total calorie requirement = Basal metabolic requirement × PAL coefficient
Example: Assume, in line with one of the previous examples, that the calorie requirement relative to basal metabolism is 1526kcal, that the athlete to be analysed is a man and that his PAL is heavy. The Schofield coefficient relating to the heavy PAL for men is 2.1. We will therefore have:
Total calorie requirement = 1526 × 2.1
Total calorie requirement ≈ 3200kcal