Energy Requirements

Energy requirements are determined by a person’s resting metabolic rate, physical activity, and the thermic effect of food (Reimers, 2008). Energy is commonly measured in kilocalories (kcal or calories) (Reimers, 2008). It is difficult to calculate a person’s energy needs due to number of factors affecting it. As a rough guide for males, those that are lightly active, moderately active, and very active should consume 38kcals, 41kcals, and 50kcals per kilogram of bodyweight respectively (Reimers, 2008). For females, those that are lightly active, moderately active, and very active should consume 35kcals, 37kcals, and 44kcals per kilogram of bodyweight respectively (Reimers, 2008). It should be stated that young athletes have a greater energy requirement than adults for growth and maturation purposes (Hannon, Unnithan, and Morton, 2020).

Additionally, calories can be added or subtracted dependent on whether the goal is to gain or lose weight. For weight gain, it is recommended to consume 350-700kcal above daily energy requirements to supply the extra calories to increase lean tissue by 0.45-0.9kg per week (Reimers, 2008). For weight loss, it is recommended to reduce daily energy intake by 500-1000kcals to lose 1% (0.5-1.0kg) of bodyweight per week (Reimers, 2008). Rapid weight loss can lead to dehydration, loss of lean tissue and a reduction in vitamin and mineral status; a more gradual weight loss maximises fat loss and preserves lean tissues. (Reimers, 2008).

Carbohydrates

Carbohydrates are the predominant energy source for the body (Reimers, 2008). Carbohydrates are stored in the liver and muscles as glycogen. Glycogen is the predominant fuel source for moderate to high-intensity exercise (Close, Kasper and Morton, 2021).

Glycaemic index (GI) refers to the ability of carbohydrate foods to raise blood glucose levels (Close, Kasper and Morton, 2021). Low-GI (<55) foods are slowly digested and takes a longer time to raise blood glucose levels (Reimers, 2008; Close, Kasper and Morton, 2021). Carbohydrates should be predominantly sourced from low-GI foods because of their reduced insulin response and therefore improved ability for the body to oxidise fats, which may be suitable for those wishing to lose body mass (Close, Kasper and Morton, 2021).

Common examples of Low-GI foods:

• All bran
• Jam (high fructose)
• Whole milk
• Sprouts
• Green beans
• Kidney beans
• Quinoa
• Chapati
• Boiled or mashed sweet potato
• Egg noodles
• White spaghetti
• Wholemeal spaghetti
• Apricots (fresh or dried)
• Peanuts
• Cashew nuts
• Strawberries
• Oranges
• Apples
• Yoghurt (fat-free)
• Apple juice
• Orange juice
• Bananas

High-GI (>70) foods are rapidly digested and raise blood glucose and insulin levels (Reimers, 2008; Close, Kasper and Morton, 2021). Due to this rapid increase in blood glucose, it may be appropriate for exercisers to consume high-GI foods following exercise to maximise glycogen resynthesis and improve recovery from exercise (Close, Kasper and Morton, 2021).

Common examples of High-Gi foods:

• Bagels
• Cornflakes
• Jam (high glucose)
• White bread
• Wholemeal bread
• Couscous
• Boiled or mashed potato
• White rice
• Baguettes
• Scones
• Pretzels
• Doughnuts
• Waffles

Carbohydrates should make up 45-65% of an individual’s total daily energy intake or 5-6 grams per kilogram of body weight (g•kg^-1) per day in adults (Reimers, 2008). Close, Kasper and Morton (2021) further suggested that carbohydrate intake should be determined by training situation. For example, injured or lightly active individuals should consume less carbohydrates (<2g•kg^-1, 2-4g•kg^-1) than that of moderately active (4-6g•kg^-1) and highly active individuals (6-8g•kg^-1).

Proteins

Proteins are vital for the large range of bodily functions including structure, immunity, and regulation of bodily systems (Close, Kasper and Morton, 2021). 10% of brain tissue, 20% of the weight of the heart, skeletal muscles, liver, and glands are comprised of protein (Reimers, 2008). Proteins are made of amino acids; 9 of which are considered essential to the human body and 11 are considered non-essential (Close, Kasper and Morton, 2021). Essential amino acids cannot be synthesised by the body and as such much must be consumed in the diet, whereas non-essential proteins can be synthesised by the body (Close, Kasper and Morton, 2021).

With many protein supplements available on the market, it is also important to identify it’s influence on protein uptake. It should be stated that supplemental protein shakes are not necessary, but they are convenient (Close, Kasper and Morton, 2021). Whey protein is considered superior for muscle protein synthesis than casein or soya-based protein, due to the speed on increasing blood amino acid concentrations (Close, Kasper and Morton, 2021). However, maintaining lean mass during weight loss may not require supplementation; intake from whole foods should be prioritised (Close, Kasper and Morton, 2021).

Complete proteins refer to proteins that contain a similar amino acid pattern required by the body, whereas incomplete proteins are proteins that lack one or more essential amino acids (Reimers, 2008). Complete proteins can be found in animal products such as eggs, meat, fish, poultry, and dairy products (Reimers, 2008). When consuming incomplete proteins (e.g., grains, beans, vegetables, and gelatine), it is important to consume a wide variety of sources throughout the day, so all essential amino acids are obtained (Reimers, 2008).

Common examples of Protein foods:

• Mature cheddar cheese
• Beef steak mince (15% fat)
• Quorn
• Salmon fillet
• Beef medallion steak
• Mixed nuts
• Turkey mince (2% fat)
• Chicken breast
• Tinned tuna
• Cod fillet

There is two ways to consider the amount of protein required per day. Protein should make up 10-15% of an individual’s total daily energy intake or 0.8 grams per kilogram of body weight (g•kg^-1) per day in adults (Reimers, 2008; Close, Kasper and Morton, 2021). For athletes, there may be a need for increased requirement for protein. Specifically, for endurance and strength athletes, protein may be needed in amounts of 1.2-1.4 g•kg^-1 and 1.8-2.0 g•kg^-1 respectively per day (Reimers, 2008; Close, Kasper and Morton, 2021). For athletes that do not fit into solely into the “endurance” or “strength” categories, there is general recommendation of 1.5-2.0 g•kg^-1 per day (Reimers, 2008). For young athletes, 1.4-2.0 g•kg^-1 of protein is recommended (Hannon, Unnithan, and Morton, 2020). When aiming to lose fat mass and retain lean mass, additional protein may be required (Close, Kasper and Morton, 2021). Protein should be regularly consumed throughout the day but consuming 20-25g of high-quality protein pre- and post-exercise may maximise protein synthesis (Close, Kasper and Morton, 2021).

Fats

While there is a focus on reducing dietary fat due to few performance enhancements, a lack of fat may reduce metabolism, testosterone production and muscle development (Reimers, 2008). However, there may be performance benefits for activities that last longer than 90 minutes. Eliminating fat from diet can lead to a reduced supply of essential fatty acids (omega 3 and omega 6) and fat-soluble vitamins A, D, E and K (Close, Kasper and Morton, 2021). Fats can be saturated or unsaturated dependent on their chemical structure (Close, Kasper and Morton, 2021). Replacement of some of saturated fats with unsaturated sources have been linked with improved body composition, cardiovascular function, and low-density lipoprotein.

Common unsaturated fat foods:

• Olive, peanut, canola, sunflower, corn, soybean, and flaxseed oils
• Avocados
• Nuts
• Seeds
• Fish

Common saturated fat foods:

• Cheese
• Whole milk
• Butter
• Red meat
• Biscuits
• Fast foods

Fats are the predominant energy source for low-intensity activities. Fats should make up 20-30% of an individual’s total daily energy intake with less than 10% coming from saturated sources (Reimers, 2008). For young persons, ~35% of an individual’s total daily energy intake with less than 11% coming from saturated sources should be consumed (Hannon, Unnithan, and Morton, 2020).

Conclusion

Consideration of energy requirements and macronutrients is important for everyone, especially exercisers, to understand. The calories consumed daily determines whether a person will gain, maintain, or lose weight. Calories that are consumed can be prioritised depending on health and fitness aims by manipulating amounts of certain macronutrients and sources of those macronutrients. Everyone should adopt a “food first” approach to nutrition, with supplementations to be used when an individual struggles to reach specific macronutrient target through whole foods (Hannon, Unnithan, and Morton, 2020). It should be stated that, while this guide may apply to many individuals, any person with specific needs should consult a registered dietician or sports nutritionist.

References:

Close, G., Kasper, A., and Morton, J. (2021) ‘Nutrition for Human Performance’ in Jeffreys, I. and Moody, J. (ed), Strength and Conditioning for Sports Performance. 2^nd Edn. New York: Routledge, pp.153-190.

Hannon, M., Unnithan, V., and Morton, J. (2020) ‘Nutritional strategies to support young athletes’ in Lloyd, R. and Oliver, J. (ed), Strength and Conditioning for Young Athletes Science and Application. 2^nd Edn. New York: Routledge, pp.300-335.

Reimers, K. (2008) ‘Nutritional Factors in Health and Performance’ in Baechle, T. and Earle, R. (ed), Essentials of Strength and Conditioning. 3rd Edn. Champaign: Human Kinetics, pp.201-234.