Body Composition 101

The human body is one of the most physiologically complex and wondrous structures known to man, consisting of various compartments that change with aging, development, growth and physical activity. Since Hippocrates attributed health to an appropriate balance of four body fluids the study of the constituent parts of the body has fascinated scientists, medics, dieters and athletes alike. Measurement of body size allows for the determination of the physical dimensions of the body whereas body composition is a technical term used to describe various components that make up body weight, namely fat-mass and fat-free mass. The latter (known also as the non-fat component) plays its role in the structural and functional component of the human body and consists in proportions of water (72%), protein (21%) and bone minerals (7%). The fat compartment of the body comprises water (20%) and adipose tissue (80%) and can vary considerably between individuals. That is, this ‘physiologically complex and wondrous structure’ is made up predominantly of water!



Monitoring changes in aging, development, growth, and physical activity enables health professionals to gain a greater understanding of one’s nutritional status, physical fitness, and disease risk. From a health standpoint, adiposity (body fatness) is correlated with a number of metabolic and cardiovascular diseases, such as type II diabetes and hypertension. On the flip side, extremely low body weight (typically ascribed by a low body fat) is linked to diseases associated with undernutrition i.e. anorexia nervosa, and diseases associated with poor musculoskeletal status i.e. osteoporosis (1). Recommended body fat percentage (BFP) varies from country to country, organisation to organisation, but the general consensus is that a normal BFP’s for women is ~20% and men is ~13-17%.

From an athletic perspective, body composition forms an essential component of success and is now considered a meaningful evaluation tool used in sports science support. When assessing body composition from an athletic standpoint it is essential that the demands of the sport are taken into consideration. For example, having a high body fat is often seen as advantageous for combat sports where fat provides an important protective buffer from physical contact. In rugby for example, increased weight and body mass is historically associated with success; a comment supported by Olds et al. (2001; 2) who revealed the final ranking in the 1999 World Cup showed significant correlations with the average mass of the squads. On the contrary, aesthetic pressure to possess low levels of body fat is often observed in sports such as gymnastics, whereas in sports such as swimming, increased levels of fat are purported to aid buoyancy and thus, an increase in fat mass can impair exercise performance. There are also advantages and disadvantages related to being a particular body size. Taller people tend to be better at sports in which reaching a high level above the ground is required, such as basketball and volleyball. Shorter people tend to be better at sports that require a rotation of the body around an axis, such as gymnastics.



A number of different techniques can estimate body composition: Bioelectric impedance (a test you may have used during your induction at the gym), hydrodensitometry (a test based on the displacement of water), skin-fold measurements, and dual-energy x-ray absorptiometry (DXA – the same technology used to measure bone mineral density). DXA is (at present) considered the gold-standard measurement of body composition due to its purported ability to measure fat to within 2 percent accuracy. The real gold standard is MRI and CT; however these are very expensive and often inaccessible.



Before I delve any deeper, I think it necessary to point out that when seeking to manipulate your body composition the primary goal should be to improve health and wellbeing – health is EVERYTHING. The secondary goal of improving body composition will often differ from person to person i.e. one person may wish to improve physical performance, another may wish to look better from an aesthetic perspective, or indeed it may be a combination of both.

For the purpose of this article, I would like to focus on improving the body composition of those who would like to reduce weight (body fat). Now, losing weight is often seen as a very complicated and confusing process which ‘works for some but not for others’ and ‘only works for a short period of time’ etc. In reality, it is often the individual which makes the process more difficult than it needs to be. The process of losing weight is actually quite simple and is centred around my first tip:



When your energy intake equals the energy expenditure you will be in energy balance.
When you eat less than you burn, you are in a negative energy balance and as a result you will lose weight.
When you eat more than you expend, you are in positive energy balance – and in this case you will gain weight.

If you are seeking to lose weight, the key principle for you to focus on is number 2. There are three ways in which you can induce a negative energy balance:

Reduce your energy intake
Increase your energy expenditure
A combination of both

A reduction in energy intake is widely recognised as the most important factor affecting weight loss amount and rate, although please do not use this is an excuse not to do any exercise! So surely this is just a simple game of maths – eat less calories than you burn and you will lose weight? Well, in short yes but this must be done in the right way that is beneficial to your health and is enjoyable and sustainable. This links me nicely to my second tip for weight loss…



One pound of fat contains 3,500 calories. Therefore, a negative energy balance of 500 kcal per day should result in the loss of 1 pound of fat per week. It is well recognised that this is a safe and effective negative energy balance that shouldn’t leave you feeling too hungry and can assist you in losing weight in a healthy and effective manner (3). Going below 1000 calories per day is not advised because it is hard to get adequate daily nutrients and this is linked to a number of metabolic and cardiovascular diseases. What’s more, you will probably be left very hungry which may compromise your level of adherence (particularly in the long term). In the first couple of weeks you may wish to start off with a gradual energy reduction of 10% or 20% to prevent yourself from feeling too hungry. The key here is to get the most from your calories by consuming the most nutrient dense and healthy foods!



Cut out refined sugars and processed foods. These tend to be energy-dense and anything but nutrient-dense! Refined sugars and processed foods are linked to a myriad of chronic diseases of which include obesity and type II diabetes. They often leave you feeling more hungry than you were before you ate and craving for food again within an hour or two after a meal (have you ever had irrepressible urges for a sweet desert after eating meal at your favourite fast food restaurant?!) Replace with low energy-density foods which are nutrient-dense and in general, possess a low-glycaemic index (GI). Construct your meals around protein sources (see below) and vegetables then add in your main carbohydrate source(s).
Excellent sources of carbohydrate include: grains (basmati and jasmine rice), oats, quinoa, kamut and buckwheat. These can be cooked and used like rice for side dishes, pilaf, soups or stews



Currently, the RDA of protein for normal healthy adults is 0.8 g/kg body mass per day, which for a 70 kg person works out to be 84 g of protein per day. However, research suggests that increasing your daily protein intake to ~1.2 g/kg (for a normally active healthy individual) can positively influence body composition by aiding weight loss (for review see 4). But how does protein assist with weight loss? Well, the power of protein is somewhat remarkable. Protein has been shown to assist with satiety and reduce voluntary food intake. High-protein foods also use more energy (when compared with carbohydrate and fat) to digest, metabolise and have been shown to reduce body fat while maintaining lean/muscle mass – which is precisely the effect you are looking for! (For more info on the power of high protein diets click here)

Excellent sources of protein include: fish, fowl, red and lean meat, whey, dairy and beans.



The misconception that fat is bad for you is slowly being phased out of many contemporary dietary regimes and rightly so. Fat is an important nutrient in the diet with a host of purposeful roles, including that of immune function, reproduction, insulation, protection, and absorption of vitamins A, D, E and K. One of the reasons fat gets a bad rap is because it is energy-dense, meaning that it contains a large number of calories per gram compared to carbohydrate and protein (9 vs. 4 vs. 4) and this can influence our feeling of fullness when on a calorie restricted diet. Excessive fat intake is also linked to a number of cardiovascular and metabolic diseases; however, contemporary research is now showing that it is in fact refined carbohydrates which are the real enemy when it comes to the prevalence of chronic disease. You should aim to reduce fat intake to ~15% of your total daily energy intake – this should help you to reduce your total daily calories while maintaining satiety. These should be sourced from healthy fats:
Healthy fats can be found from:

  •    Olive and canola oils
  •     Unsalted nuts
  •     Seeds
  •     Olives
  •     Eggs (with yolk!)
  •     Cold-water fish such as herring, mackerel, tuna, salmon and sardines
  •     Red meat – often and unfairly labelled as ‘the enemy.’ Red meat (when consumed in moderation) has an excellent fatty acid profile – high in oleic acid and is also a great source of B vitamins, CLA, protein, iron, zinc, selenium and antioxidants such as ubiquinone.
  •     If vegetarian, purslane and algae are fantastic sources of omega 3

Unhealthy fats can be found from:

  •     Chips
  •     Crackers
  •     Margarine
  •     Donuts
  •     Cakes and cookies etc.



Water makes up about 72% of your body and is required for all bar none of its processes. What’s more, dehydration can cause hunger i.e. sometimes when you feel hungry it isn’t because your body needs food it’s because it’s craving water. Research shows that consumption of water, before or during meals, helps individuals manage their body weight by increasing satiety (feeling of fullness) and/or reducing food intake. Take for instance a recent study by Stookey et al. (2010; 5) who found that increasing self-reported daily water consumption by ≥1 L in overweight women was associated with increased weight loss of ∼2 kg, during a 12-month dietary intervention, compared with women who consumed <1 L water daily. In another study, researchers found both normal-weight and overweight/obese middle-aged and older adults ingested less energy during an ad libitum meal, when given a 500 mL water preload, 30 min prior to the meal (versus a no-preload meal condition; 6).
The amount of water a person needs to drink to remain hydrated varies depending on a number of factors, including size, the temperature and how active they are. As a general guideline, people should drink about 1.2-1.5 litres of water per day, consumed at regular intervals throughout the day.


Concluding Thoughts

It is important to look after your body to ensure good health and well-being. By understanding the fundamental principles of body composition, particularly the ways in which it can be manipulated via both diet and exercise you are putting yourself at the forefront of achieving the most of what your body has to offer. What is also important to understand is that nobody is perfect and that being overly stringent with your diet and exercise regime can be hazardous to health. Eat well, exercise regularly, enjoy what you’re doing and don’t be afraid to have the occasional carb re-feed or lazy day in bed!



1. Gibson, A., Mermier, C., Wilmerding, V., & McKinnon, M. (2009). Body fat estimation in Collegiate athletes: An update. Athletic Therapy Today, 14, 13-16.
2. Olds, T. (2001). The evolution of Physique in male rugby union players in the twentieth century. Journal of Sports Science, 19, 253-262.
3. Burke, L., & Deakin, V. (2010). Clinical Sports Nutrition. North Ryde, NSW; McGraw Hill.
4. Westerterp-Platenga, M. S., Lemmens, S. G., & Westerterp, K. R. (2012). Dietary protein – its role in satiety, energetics, weight loss and health. British Journal of Nutrition, 108, 105-112.
5. Stookey, J. D., Constant, F., Popkin, B.M., et al. (2008). Drinking water is associated with weight loss in overweight dieting women independent of diet and activity. Obesity, 16, 2481–2488.
6. Van Walleghen, E. L., Orr, J. S., Gentile, C. L., et al. (2007). Pre-meal water consumption reduces meal energy intake in older but not younger subjects. Obesity, 15, 93–99.



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