Body Composition

One of the major factors of managing body composition is related to the amount of energy that a person expends. Human energy expenditure is a form of internal heat generation and the term that is used to discuss this phenomenon is Thermogenesis.

On a daily basis, the approximated division of energy consists of:

• 60-70% conducting normal tasks such as thermoregulation and breathing, pumping blood and other bodily functions. This is known as the Basal Metabolic Rate.

• 10%  for food digestion. The energy use generates heat, therefore this process is known as the Thermic Effect of Food. Different foods are easier or more difficult for the body to transfer into usable energy and thus there are variances in the amount of energy required for digestion. 

• 20-30% for undertaking movement and physical exercise. The energy use generates heat, therefore this process is known as the Thermic Effect of Exercise. The range in the percentage amount in this category takes into consideration the wide range of physical activity that different people undertake each day. Whilst all physical activity requires energy, some such as general movements like standing, walking, and fidgeting with the hands requires much less energy than high-intensity exercise routines. 

Energy intake is the food and beverages that are consumed by a person during the day. The higher the energy intake, the more 'spare energy' that the body will have, any spare energy will be stored as fat. The average adult requires approximately 8700 kilojoules (or 2080 calories) per day to maintain a healthy weight. This will vary depending on daily activity levels, age, gender, genes, and lifestyle There are various online tools and apps that can be utilised to keep track of daily kilojoule intake. Examples include MyFitnessPal and Foodswitch by Bupa. 

Achieving a balance between energy expenditure and energy intake is the key to maintaining healthy body composition. Essentially a balance is achieved if the energy that is consumed is equal to the energy that is expended. If more food is consumed that is required by the body it is stored as excess weight. Likewise, if more physical activity occurs than the body has immediate fuel for then weight loss is the result.

The following video explains how physical exercise and healthy eating effects this balancing process.

The human body is like a machine, except rather than metal and batteries it is comprised of cells, tissue, blood and other matter. The fuel that keeps our 'machine' going is energy, measured in the form of kilojoules and our bodies convert the food we consume and the beverages we drink into energy through a process known as metabolism. 

This process consists of two types of chemical reactions:

1. Catabolism - The breaking down of substances into smaller molecules, releasing of essential nutrients and creating energy.

2. Anabolism - The process by which the body utilises the energy released as part of catabolism for the growth and repair of cells.

Metabolism is occurring constantly, however, the rate or speed of the process does vary. Resting Metabolic Rate (RMR) refers to the amount of energy your body requires to function whilst at rest, it is similar to Basal Metabolic Rate (BMR) because both determine how much energy the body is consuming just to maintain homeostasis, however, it differs in the timeframe that it is typically measured. Basal Metabolic Rate is usually taken in the morning, prior to eating, when physical activity hasn't occurred in the last 24 hrs and stress levels are very low. Resting Metabolic Rate is taken at any resting period. 

Metabolism can be affected by the following factors:

• Nutrition - Eating too few kilojoules can slow the metabolism as the body attempts to conserve energy. Alternatively eating a diet that is high in processed foods, sugar, fat, and/or salt can affect metabolism, as there may be limited essential nutrients and also certain types of foods, are processed faster by the body (high glycaemic index foods) resulting in more food being consumed.

• Muscle Mass - The greater the mass of your muscles the heavier demand on the body to produce energy.

• Genetics - Certain people are predisposed to genetic conditions, such as hyperthyroidism, which cause hormone imbalances that affect metabolism.

• Physical Activity - Increased physical activity forces the body to burn energy faster.

• Body Composition and Demographic - Body size, gender, and environment can all influence metabolism.

• Age - As we get older our metabolism naturally slows and muscle mass decreases. 

• Drugs - Certain medications and drugs such as antidepressants and steroids can influence metabolism.

Humans can only withstand 10°  drops and 5° rises in body temperature. Ideal human body temperature is considered to be 36.8°C. Maintaining optimal body temperature (even when surrounding temperatures are extreme) is known as thermoregulation and it is controlled by the Hypothalamus which is located within the brain. Thermoregulation is one aspect, among others, of Homeostasis, which is the stability of an organism's internal conditions.

There are a number of ways that thermoregulation occurs, the two most common are:

• Sweating when the body temperature rises.

• Shivering when the body temperature drops.

Shivering forms part of a larger process known as Thermogenesis which literally translates to heat production. Thermogenesis was briefly discussed earlier in this topic in regards to the amount of energy that a person expends on a daily basis. In that section, the three divisions of energy were: Basal Metabolic Rate (60-70%), Digestion (10%), and Physical Activity (20-30%). 

In relation to Basal Metabolic Rate there are two forms of thermogenesis:

• Shivering - Occurs through the involuntary physical movement of skeletal muscle and does not involve body fat as a means of heat production. It is an early response to prevent conditions such as hypothermia.

• Non-Shivering - Occurs through brown adipose tissue (brown fat). This type of tissue (which is packed with iron-rich mitochondria making it brown in appearance) exists in small quantities in adult humans (babies have a higher percentage) and its primary purpose is to burn fat for the purposes of heat generation.

In addition to maintaining the basal metabolic rate, thermogenesis also plays a role in weight loss, and thus body composition. The body utilises energy, and thus creates heat (thermogenesis), to facilitate physical activity and also digest food. The body's internal regulation system is quite sensitive to changes in energy intake and expenditure (ie. dieting and exercise) and will adapt the metabolism accordingly to try and persevere energy reserves. This is known as Adaptive Thermogenesis.  

There are three types of adaptive thermogenesis:

• Exercise-associated thermogenesis (EAT) - This is the participation in sustained exercise-related physical activity such as playing sports, hiking, swimming or visiting a gym. 

• Non-exercise activity thermogenesis (NEAT) - This is the undertaking of all other types of activity such as household chores, work-related tasks like typing, and posture-related movements such as sitting, standing, and walking. 

• Diet-induced thermogenesis (DIT) - The process that occurs as a result of digesting food and can be affected by eating different types of foods or by taking certain supplements. For example, digesting carbohydrates requires less energy than protein. This process and its associated variations regarding energy required is known as the thermic effect of food.

As the body enters a state of adaptive thermogenesis it may experience changes in the following hormones:

• Leptin - A hormone which is stored within fat cells and helps to inhibit hunger and regulate energy balance. When leptin levels drop (ie. through dieting) feelings of hunger and even cravings for certain foods often occur.

• Insulin - A hormone that helps to transport glucose from food into cells where it can be used as energy. Certain foods (ie. carbohydrates) will result in higher insulin production and an over-reliance on glucose as an energy source rather than fat.  Whilst a certain amount of glucose is required for efficient energy production it must be balanced well with other types of energy sources if healthy body composition is to be maintained.

• Thyroid hormone - One key function of this hormone, among other functions, is to regulate metabolism. Low levels of thyroid hormone often result in weight gain (a condition known as hypothyroidism), in contrast, higher levels of thyroid hormone can cause a person to lose weight unexpectedly (a condition known as hyperthyroidism).

Body fat is found all over the body including in muscle tissue, under the skin, and around organs. A certain amount of fat is required by the body to protect organs, provide fuel for energy and help with hormone regulation. However, this level of essential fat is quite small as seen in the below percentage amounts, any additional fat is known as excess fat:

• 2 - 5% in men.

• 10 - 13% in women. Women have more fat due to the hormone oestrogen which reduces the ability to burn energy after eating. Increased body fat benefits women during child-bearing age as more body fat is required during pregnancy.

On the surface, it seems simple to lose weight (fat loss), reduce the number of kilojoules being consumed and also exercise more. However, the human body is a complicated organism and this is not always a straight forward process.

As mentioned earlier in this topic, the human body is quite sensitive to changes in energy expenditure. Reducing kilojoules (calories) through dieting will result in the body having less available energy to burn to undertake physical exercise and maintain the basal metabolic rate. This, in turn, means that overall movement will be less and in extreme situations, the body may go into a protective state known as 'starvation mode' in which the metabolism is slowed to preserve as much fat content as possible until energy intake is re-established. 

Many diets will result in fat loss, sometimes dramatically, however, if not properly managed they are often unsustainable as they require a constant restrictive approach to kilojoule counting, cutting out or severely restricting whole food groups, and often result in undesirable side effects and feelings of missing out (especially during social events). In many individuals, this results in a collapse of the diet after a few weeks/months and often a regain of all the lost body fat, and sometimes even more fat being applied. This is known as the Yo-Yo diet effect, and it can be quite disheartening.

This is not to say that dieting is ineffective, just that it should be undertaken with due care and under some form of professional guidance (medical or allied health professional) in addition to your expertise as a fitness professional. 

The recommended methods of reducing excess body fat levels and therefore improving body composition and hopefully improving one's body image are to eat reasonably portioned nutritionally balanced foods and undertake regular fitness activities. How clients set, work towards, and achieve their body composition goals will differ depending on their starting point, motivation levels, underlying health conditions, and the ideal physique they are aiming for.

Certain foods/drinks should definitely be reduced and only consumed sporadically (if at all), such as:

• Sugary drinks such as cordials and soft drinks.

• Junk food such as burgers, pizza, and deep-fried foods.

• Simple carbohydrates such as white bread, sugar, pasta.

• Lollies, chocolate, cake, and other high sugar content foods.

• High-salt foods.

• Highly processed foods with artificial preservatives, additives, and sweeteners.

A slow and steady approach to weight loss is recommended. This approach will prevent the body from entering 'starvation mode' and also ensure that adequate nutrients and vitamins are being consumed to allow for exercise to occur. The main physiological changes which occur as a result of undertaking regular exercise are:

• Cardiovascular endurance (physical fitness) increases.

• Muscle mass is gained (hypertrophy) resulting in greater strength. 

• Weight loss, especially when combined with healthy eating. 

Muscles require significant energy to sustain themselves and therefore the body will draw on the reserves it has available. If the individual is eating a healthy diet with limited intake of simple carbohydrates (the fastest and easiest source of energy) the body is forced to utilise its excess fat stores to attain the necessary sustenance and thus body composition improves. 

There are various methods and systems used to measure and classify body composition:

There are benefits and limitations to all of the above body composition appraisal methods. 

• Benefits - They provide a good starting point to determine if someone is overweight or obese. Whilst this may be obvious in some cases is much less apparent in borderline instances. Society has become accustomed to people looking a certain way and carrying additional weight, therefore, people are sometimes surprised to find out that they are not as healthy as they thought. Another benefit is that they allow progression to be mapped, highlighting goal benchmarks. Some of the measurement methods are extremely accurate and are used in not only fitness environments but also medical fields (ie. Somatotype classification and Bio-electrical impedance analysis).

• Limitations - Some methods only provide a rudimentary guide. Height and weight charts and also BMI calculators do not take into consideration lean body mass which in some people (ie. bodybuilders and others with lots of muscle mass) can be quite significant. It is always recommended that these appraisal methods are used in combination with other testing such as girth measurements. Some of the tests can be complicated to perform (ie. Somatotype classification and skinfold measurements) and require training on how to utilise the measurement devices. Bodyweight also fluctuates quite significantly throughout the day and also during the week depending on foods eaten and exercise performed, therefore, multiple tests may be required to determine accurate results.

There are different factors which may affect a client's weight and also their measurements and calculations which must be taken into consideration:

Body fat is the main factor affecting a client's weight. As mentioned earlier, a certain amount of fat is required by the body for protective, energy, and hormonal purposes, however, the majority of individuals have excess amounts of fat.

Lean body mass compromises bones, muscles, organs, tissue, and also water. Bones, organs, and tissue weight will not change significantly from person to person and generally do not fluctuate. However, muscle mass and water weight may affect weight measurements and calculations. 

Muscles that have commenced hypertrophy will be increasing in size and therefore overall weight. This is why some tools used for determining body composition, such as body mass index (BMI) calculators, are not effective for people with well-developed muscles.

Water makes up a significant portion of lean body mass (up to 55% of total body weight in a healthy male) and it is vital to maintaining a healthy body. However, excess water can be retained by the body and thus add to overall body weight. Water weight can be caused by:

Finally, clothing can affect someone's weight and measurement calculations. General clothing and shoes can add up to 4 kilograms of weight. Therefore, it is important that any excess or heavy clothing items are removed prior to measurements taking place and similar outfits are worn for all measurement activities. 

Fitness professionals must be aware of the signs and symptoms of unhealthy eating practices and be prepared to refer clients to appropriate medical or allied health professionals where necessary. Remember, the duty of care for fitness professionals advises against providing specific dietary advice to individuals. 

Extreme diets can result in significant rapid weight loss, which can be a major cause for concern if not properly supervised. Apart from the actual weight loss, some other signs that a person may be on an extreme diet and thus not receiving adequate energy intake include:

• Feelings of depression (may also be a sign of other unrelated conditions) - Depression or low mood is often the result of a reduction in essential vitamins and minerals such as Vitamin B, D, and Zinc.

• Constipation - The removal of fibre-rich foods such as complex carbohydrates and fruits/vegetables may result in constipation.

• Feeling cold - The body's ability to perform basic thermoregulation tasks reduces as energy intake is reduced and fat content is lowered, this results in a drop in body temperature.

• Feeling lethargic - The body will try and conserve as much energy as possible by not performing as many physical activities (both exercise-related and non-exercise activity) thus people may feel lethargic or 'flat'. 

• Hair loss - The reduction in essential vitamins, minerals, protein, and fatty acids may result in hair loss.

Appropriate medical professionals include general practitioners (GPs) who can provide specific nutritional advice, properly supervise diets, run diagnostic tests, and also treat other medical conditions which may be apparent. Appropriate allied health professionals (who may work in collaboration with a GP) include dietitians and nutritionists. These professionals can develop healthy eating plans, supervise diets, and provide accurate resources on healthy eating and nutrition.