5.2 Energy balance and body composition

Energy balance and body composition are crucial concepts in nutrition and athletic performance. They involve the relationship between energy intake, expenditure, and storage, which directly impact an athlete's body composition and overall health.

Understanding these principles allows athletes and coaches to manipulate energy balance for specific goals. Whether aiming for weight loss, muscle gain, or performance optimization, tailoring energy intake and expenditure is key to achieving desired outcomes in strength and conditioning.

Energy balance and its components

Definition and components of energy balance

Top images from around the web for Definition and components of energy balance

• 

  Frontiers | Low Protein Diets and Energy Balance: Mechanisms of Action on Energy Intake and ... View original

  Is this image relevant?

• 

  Energy Balance | Nutrition View original

  Is this image relevant?

• 

  Energy and Heat Balance | Anatomy and Physiology II View original

  Is this image relevant?

• 

  Frontiers | Low Protein Diets and Energy Balance: Mechanisms of Action on Energy Intake and ... View original

  Is this image relevant?

• 

  Energy Balance | Nutrition View original

  Is this image relevant?

1 of 3

Top images from around the web for Definition and components of energy balance

• 

  Frontiers | Low Protein Diets and Energy Balance: Mechanisms of Action on Energy Intake and ... View original

  Is this image relevant?

• 

  Energy Balance | Nutrition View original

  Is this image relevant?

• 

  Energy and Heat Balance | Anatomy and Physiology II View original

  Is this image relevant?

• 

  Frontiers | Low Protein Diets and Energy Balance: Mechanisms of Action on Energy Intake and ... View original

  Is this image relevant?

• 

  Energy Balance | Nutrition View original

  Is this image relevant?

1 of 3

• Energy balance is the relationship between energy intake and energy expenditure
• A positive energy balance occurs when intake exceeds expenditure, while a negative energy balance occurs when expenditure exceeds intake
• The components of energy balance include:
  • Energy intake (calories consumed through food and drink)
  • Energy expenditure (calories burned through physical activity and bodily functions)
  • Energy storage (calories stored as body fat or glycogen)

Factors contributing to energy expenditure

• Basal metabolic rate (BMR) is the minimum number of calories required to sustain vital functions at rest and is a significant component of daily energy expenditure
  • BMR accounts for approximately 60-70% of total daily energy expenditure in sedentary individuals
  • Factors influencing BMR include age, sex, body size, and body composition
• Thermic effect of food (TEF) refers to the energy expended during digestion, absorption, and metabolism of nutrients, and accounts for a small portion of daily energy expenditure
  • TEF typically represents about 10% of total daily energy expenditure
  • The magnitude of TEF varies depending on the macronutrient composition of the meal (protein has the highest TEF, followed by carbohydrates and fats)
• Non-exercise activity thermogenesis (NEAT) encompasses energy expended through daily activities other than structured exercise
  • Examples of NEAT include fidgeting, posture maintenance, and spontaneous muscle contractions
  • NEAT can vary significantly between individuals and is influenced by factors such as occupation, lifestyle, and genetics

Energy balance and body composition

Relationship between energy balance and body composition

• Body composition refers to the relative proportions of fat mass and fat-free mass (muscle, bone, organs, and water) in the body
• Energy balance directly influences body composition
  • A chronic positive energy balance leads to an increase in body fat
  • A sustained negative energy balance results in a decrease in body fat
• The degree of energy imbalance determines the rate of change in body composition
  • A larger energy surplus or deficit will result in more rapid changes compared to smaller imbalances
  • For example, a daily energy surplus of 500 calories will lead to faster weight gain than a surplus of 200 calories

Factors influencing body composition changes

• The macronutrient composition of the diet (carbohydrates, proteins, and fats) can influence body composition changes
  • Higher protein intakes are more favorable for maintaining or increasing muscle mass during periods of energy restriction
  • Adequate protein intake (1.6-2.2 g/kg/day) is recommended for athletes to support muscle protein synthesis and recovery
• Resistance training can help preserve or increase muscle mass during periods of negative energy balance
  • Engaging in regular resistance training (2-3 sessions per week) can minimize the loss of fat-free mass during weight loss
  • Resistance training provides a stimulus for muscle protein synthesis and helps maintain muscle mass and strength

Energy requirements for athletes

Estimating energy requirements

• Estimating energy requirements for athletes involves calculating their total daily energy expenditure (TDEE), which is the sum of their BMR, TEF, NEAT, and exercise energy expenditure (EEE)
• BMR can be estimated using predictive equations such as the Harris-Benedict or Mifflin-St Jeor equations, which take into account factors like age, sex, height, and weight
  • Example: For a 25-year-old male athlete (height: 180 cm, weight: 75 kg), the Mifflin-St Jeor equation estimates a BMR of approximately 1,800 calories per day
• TEF is typically estimated as 10% of TDEE, while NEAT can vary significantly between individuals and is often estimated based on lifestyle and occupation
• EEE can be calculated using metabolic equivalents (METs) for specific activities, or by measuring oxygen consumption during exercise and converting it to caloric expenditure
  • Example: Running at a pace of 10 km/h (6 METs) for 60 minutes would result in an EEE of approximately 600 calories for a 75 kg athlete

Factors influencing energy requirements

• Athletes engaging in high-volume or high-intensity training will have greater energy requirements compared to those with lower activity levels
  • Endurance athletes (runners, cyclists, swimmers) may require 2-3 times their BMR to support their training and competition demands
  • Strength and power athletes (weightlifters, sprinters) may require 1.5-2 times their BMR, depending on their training volume and intensity
• Specific energy requirements may vary based on an athlete's goals
  • Athletes aiming to increase muscle mass may require a positive energy balance (caloric surplus) to support muscle growth
  • Athletes seeking to decrease body fat may need to maintain a negative energy balance (caloric deficit) to promote fat loss

Strategies for manipulating energy balance

Strategies for weight loss and fat reduction

• To promote weight loss and fat reduction, athletes can create a moderate energy deficit by reducing caloric intake and/or increasing energy expenditure through exercise
• A safe and sustainable rate of weight loss is typically 0.5-1% of body weight per week, which equates to a daily energy deficit of 500-1000 calories
  • Example: For a 75 kg athlete, a safe weight loss rate would be 0.375-0.75 kg per week, achieved through a daily energy deficit of 500-1000 calories
• Nutrient timing can be optimized to support body composition goals
  • Consuming protein and carbohydrates before and after workouts can promote muscle protein synthesis and recovery
  • Distributing protein intake evenly throughout the day (every 3-4 hours) can help maintain muscle mass during periods of energy restriction

Strategies for muscle gain

• To support muscle gain, athletes should maintain a slight positive energy balance (caloric surplus) of approximately 10-20% above their TDEE, in combination with a high-protein diet and progressive resistance training
  • Example: For an athlete with a TDEE of 3,000 calories, a caloric surplus of 300-600 calories per day would support muscle gain
• Resistance training should be performed 3-4 times per week, focusing on progressive overload and targeting all major muscle groups
• Adequate protein intake (1.6-2.2 g/kg/day) is necessary to support muscle protein synthesis and hypertrophy

Monitoring and adjusting energy balance strategies

• Periodizing energy intake and expenditure can be effective for athletes with specific body composition goals
  • Increasing caloric intake during phases of intense training can support recovery and adaptation
  • Decreasing caloric intake during periods of reduced training or competition preparation can help optimize body composition
• Regular monitoring of body composition, using methods such as skinfold measurements, bioelectrical impedance, or dual-energy X-ray absorptiometry (DXA), can help assess progress and guide adjustments to energy balance strategies
  • Skinfold measurements involve measuring subcutaneous fat thickness at specific body sites using calipers
  • Bioelectrical impedance estimates body composition based on the resistance of body tissues to electrical current
  • DXA scans provide detailed information on body composition, including bone mineral density, lean mass, and fat mass