Athletes often need to modify body composition by gaining muscle, losing fat, or both. The first step is estimating caloric needs using factors such as genetics, body composition, training program, and age.
Key components of energy requirements:
- Basal metabolic rate (BMR): Accounts for 65-70% of daily energy expenditure.
- Physical activity energy expenditure: Highly variable and increases with training volume and intensity.
- Thermic effect of food: Energy used for digestion, absorption, and storage of food (~10-15% of total expenditure).
Weight gain strategies
Athletes can gain weight by:
- Eating more calories, increasing meal frequency, and prioritizing calorie-dense foods.
- Ensuring sufficient protein intake (1.5-2.0 g/kg body weight) to support lean mass gains.
- Overfeeding studies suggest high-protein diets lead to more lean mass gains, whereas low-protein diets lead to excess fat gain.
- Creatine monohydrate supplementation can further support lean body mass increases.
Practical recommendations:
- Increase meal frequency and add snacks between meals.
- Choose nutrient-dense foods with higher protein and calorie content.
- Monitor intake and adjust based on weight changes.
Estimated daily calorie needs for athletes
| Activity Level
|
Male (kcal/lb)
|
Female (kcal/lb)
|
| Light (e.g., walking, low-intensity tasks)
|
17 kcal/lb
|
16 kcal/lb
|
| Moderate (e.g., running, weight training, skiing)
|
19 kcal/lb
|
17 kcal/lb
|
| Heavy (e.g., intense training, basketball, soccer)
|
23 kcal/lb
|
20 kcal/lb
|
Weight (fat) loss
Athletes in various sports may need to reduce body fat to enhance performance in
speed, endurance, or weight-class-based competitions. Managing weight can also
provide a psychological advantage.
Despite the abundance of diet plans, there is no single “best” diet for all athletes.
Research shows that both low-carbohydrate and low-fat diets can be effective,
provided total calorie intake is reduced below maintenance needs.
Key findings on weight loss diets:
- Total calorie intake and adherence are the most important factors for
successful fat loss.
- Initial weight loss is often rapid due to water loss, particularly in low-
carbohydrate diets.
- Protein intake should be maintained to preserve muscle mass. Some
sources suggest higher intakes 1.8–2.7 g/kg body weight per day, particularly
during energy deficits. For exam purposes, the recommended range is
1.0–1.7 g/kg body weight per day.
- A moderate energy deficit (~500 kcal/day) is recommended for sustainable
fat loss.
- Behavioral therapy and social support can improve long-term weight
management success.
Overweight and obesity
Overweight and obesity are classified based on body mass index (BMI):
- Overweight: BMI of 25-29.9 kg/m²
- Obesity: BMI of ≥30 kg/m²
Health risks associated with obesity:
- Increased risk of hypertension, cardiovascular disease, type 2 diabetes, osteoarthritis, sleep apnea, and certain cancers.
The causes of obesity are complex and multifactorial, involving genetic, environmental, social, and behavioral factors. Treatments may include:
- Dietary therapy
- Increased physical activity
- Behavior modification
- Pharmacotherapy or surgery (in severe cases)
A realistic goal for overweight or obese individuals is to lose 10% of their initial weight within six months.
Low-carbohydrate diets
Low-carbohydrate diets are popular for short-term weight loss due to:
- Rapid water weight loss when glycogen stores are depleted.
- Higher protein intake, which increases satiety and thermogenesis.
- Increased fat oxidation, particularly in active individuals.
However, long-term adherence can be challenging. Athletes should carefully balance carbohydrate intake to avoid performance declines.
Calculating BMI
BMI estimation formulas:
- Metric formula: BMI = weight (kg) ÷ height (m)²
- Imperial formula: BMI = weight (lb) ÷ height (in)² × 703
Classification of adult BMI and associated disease risk
| Classification
|
BMI (kg/m²)
|
Disease risk
|
| Underweight
|
<18.5
|
Low*
|
| Normal weight
|
18.5-24.9
|
Average
|
| Overweight
|
25-29.9
|
Increased
|
| Obesity I
|
30-34.9
|
High
|
| Obesity II
|
35-39.9
|
Very high
|
| Extreme obesity III
|
≥40
|
Extremely high
|
*BMI may overestimate body fat in athletes with high muscle mass and underestimate it in older individuals.
Rapid weight loss
Rapid weight loss (RWL) is defined as losing weight faster than what is achievable through caloric restriction alone.
Common RWL methods:
- Fasting
- Dehydration (diuretics, sauna, excessive clothing)
- Self-induced vomiting or laxative abuse
- Extreme calorie restriction
Risks of rapid weight loss:
- Loss of lean body mass
- Fatigue and mood swings
- Dehydration, dizziness, and suppressed immune function
- Electrolyte imbalances, kidney failure, and in severe cases, death
Coaches and strength professionals should recognize signs of disordered weight loss behaviors and refer athletes for appropriate care.
