Exercise physiology diet & nutrition 2.1.2 Energy Balance & Optimal Weight Learning Objective: To understand optimal weight for performance including energy balance, energy intake and expenditure.

ENERGY INTAKE = ENERGY EXPENDITURE  CONSTANT BODY WEIGHT Energy Balance The food we eat is the energy supply for our body to work. How many calories (kcal) we need per day is dependent on our level of activity, age, height and weight. If the amount of energy we consume in our diet is equal to the energy we expend through our daily tasks and activity, body weight will remain constant. ENERGY INTAKE = ENERGY EXPENDITURE  CONSTANT BODY WEIGHT Energy Intake

Kilojoules, kilocalories and calories No need to make notes on this, it’s just for your interest: Kilojoules, kilocalories and calories can cause confusion. A calorie is the amount of energy needed to heat one gram of water by one degree celcius. A kilocalorie is technically 1000 calories but the two terms have come to be used interchangeably and therefore effectively mean the same thing. A kilojoule is just another unit of measurement for energy. 1 kilocalorie = 4.2 kilojoules. You don’t need to know any of this, I just thought it was interesting.

Positive Energy Balance If an individual has an energy intake (from their diet) greater than their energy expenditure (from the activity level), they will have a “positive” energy balance. They will essentially have unused energy left over at the end of the day. ENERGY INTAKE > ENERGY EXPENDITURE  INCREASED BODY WEIGHT Excess carbohydrates from food is stored as glycogen for later use. Once glycogen stores are filled, remaining carbohydrates and excess fat intake are stored as fat around major organs, underneath the skin and in skeletal muscle.

Negative Energy Balance Individuals looking to control their body weight (possibly after a period of weight gain) will need to shift the energy balance so that energy output is greater than energy intake. ENERGY INTAKE < ENERGY EXPENDITURE  DECREASED BODY WEIGHT This is most successful through a combination of decreased intake from food and increased expenditure from physical activity.

Basal Metabolic Rate BMR is the minimum amount of energy required to keep our body functioning. The Harris-Benedict Equation (below) is used to estimate BMR using height (cm), weight (kg), and age (years), men: kcal/day = (13.75 x Wt) + (5 x Ht) - (6.76 x Age) + 66 women: kcal/day = (9.56 x Wt) + (1.85 x Ht) - (4.68 x Age) + 655 TASK: Calculate your estimated Basal Metabolic Rate! REMEMBER: This is only the amount needed to maintain basic bodily functions! Any activity above resting would require additional energy intake to maintain the energy balance.

Basal Metabolic Rate + Activity Level Once you have your BMR you can estimate your required energy intake using the following calculations.

Calorie Intake Recommended daily calorie intake (for the general population) is 2000kcal for females and 2500kcal for males. We would need to reduce our kcal intake by 500kcal a day to lose between 0.5 a 1kg a week. Diet and physical activity are the key components to weight loss or gain. Which type of physical activity is best for weight loss? Long duration, low intensity exercise will burn fat. Strength training will not burn fat directly but the increased BMR as a result of greater muscle mass will lead to fat being used more when at rest. Diet v Exercise for weight loss

Energy Usage

ELT Note the food you eat over the course of the day tomorrow. To begin with this can be noted in the notes on your phone etc (something easily accessible for you to update throughout the day). Then, go to NHS calorie counter and use the search tool to complete a table of your energy intake throughout the day. Bigger meals will have to be broken down into their ingredients. For example spaghetti bolognese into spaghetti, minced beef, tomatoes, onions etc. FOOD PORTION KCAL MUESLI 100G 355 MILK 1 CUP 135

Body Fat This is example data for body fat percentages of trained and untrained individuals in different age groups.

Visual representation of body fat percentages

Is food X fattening? Could you become fat on a diet of foods which contained 0% fat? All foods have the potential to be fattening. If you take in more energy than you need then the excess energy will eventually be stored as fat.

Optimal Body Weight Place activities along the spectrum as a representation of the optimal weight to be successful in that sport. Low body weight High body weight Rugby Football High jump Gymnastics Boxing Sumo wrestling Netball Tennis Hockey

Individuals have to first reach optimal weight and then try to maintain it. To reach optimal weight for their sport some individuals might need to lose weight. This is achieved by a Negative Energy Balance… Energy intake < Energy expenditure Others might have to gain weight to reach optimal weight for their sport. This is achieved by a Positive Energy Balance… Energy intake > Energy expenditure Once optimal weight has been reached, it is maintained by a neutral energy balance… Energy intake = Energy expenditure Nutrition Gareth Bale

Using a team game as an example, explain why two positions may have different optimal weights. (4) Points need to be linked to reasons: For example: In Rugby forwards need to be heavier than backs to allow more force production in the scrum Backs need to be lighter in weight therefore than a forward, to be able to sprint at faster speeds. Points need to be linked to the explanation. Allow any two suitable examples from one team game to support points – they must be two contrasting examples.