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Calories, Kilojoules, Joules, Kilocalories…

The fitness industry is full of confusing terms, particularly when it comes to energy intake and output. Please note, calories are not the be-all, end-all when it comes to weight loss. It is possible to lose weight without counting calories.

Calories (Cal) and kilojoules (kJ) are simply a unit of measurement.

· 1 calorie = 4.2 kilojoule

· 4.2 kilojoules = 1 calorie

In Australia, kilojoules are the standard unit to measure the energy in food, based on one gram of a macronutrient:

· Carbohydrate = 17kJ/ g or 4 Cal

· Protein = 17kJ/ g or 4 Cal

· Fat = 38kJ/ g or 9 Cal

· Alcohol = 29kJ/ g or 7 Cal

In other words, for each gram of macronutrient, a specific amount of energy is provided to the body. Fats are more energy dense (more energy per gram) compared to carbohydrates and protein, which are less energy dense.

When these macronutrients are consumed in the diet through food, it provides the body with dietary energy. It is important to consume food for energy as it is required for a range of body functions:

· Movement and physical activity

· Growth and regeneration of body tissues (muscle, bone, blood, connective tissue, hair, skin, nails)

· Organ function

· Body temperature maintenance

· Muscle function and growth

Energy intake and calorie requirements

Energy expenditure relates to the total amount of energy required to maintain body function and the energy cost of physical activity. Even rest, sleep, talking and digestion cost the body in energy. The energy required for the body to function is known as the Basal Metabolic Rate (BMR). Age, gender, physical activity level, health status, weight, and height all contribute to an individual’s BMR. On average, female have a BMR of 5900kJ/day, and males 7100kJ/day to support normal body function. Everyone requires different energy intakes, dependent on their physical activity levels and body composition goals.

Individual energy requirements can be determined using the Eat for Health Government resource:

Deficit, Maintenance, Surplus

Common terms used in the fitness, calorie deficit, maintenance and surplus refer to the amount of energy intake based on body composition goals. Independent of calorie consumption, sufficient micro- and macro-nutrient intake should be ensured to promote health and wellbeing and reduce the risk of developing chronic diseases.

· Calorie deficit is consuming an energy intake below what the body requires, and if done correctly can lead to weight loss. It is recommended to keep calorie deficit phases short-term to reduce potential health risks.*

· Calorie maintenance is the energy intake required to maintain all body functions and weight.

· Calorie surplus is consuming a higher energy intake to increase weight and/or muscle mass.

Calories and fat loss

It is important to know, 1kg of fat is made up of 7700 calories (32,340 kJ). In theory, to lose 1kg of fat, a calorie deficit of 7700 calories (over a reasonable period) is required. 0.5 - 1kg of weight loss per week is a sustainable calorie deficit*. However, there are many other factors to consider when it comes to weight loss.

Calories and protein

Remember, for every gram of protein consumed, the energy intake is 4 calories (16 kJ). This makes it impossible to get a ‘no’ or ‘lower calorie’ protein powder. The fewest amount of calories a protein powder can contain is those that come from the protein itself.

For example, a 30g serve of protein powder that contains 100% protein would be 120 calories (4 cal x 30g). However, protein powder itself can never contain 100% protein. Naturally, carbohydrates and fats exist in protein powder at a very small percentage (generally 1-5%). For reference, our WPI protein powder consists of 80% protein, 5% carbohydrate and 5% fat (remaining is moisture content), adding up to 108 Cal per 30g serve .

When protein is consumed following a workout, the calories get incorporated into the muscle. This suggests that rather turning into fat, protein is utilised by the body to build and repair muscle.

*It is important to note, long-term or very restrictive calorie deficits can affect metabolism rates. If energy intake is of concern, please talk to a health professional.


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