Athletes often need to change body composition by gaining muscle, losing fat, or doing both. A good starting point is to estimate your daily calorie needs. This estimate depends on factors such as genetics, current body composition, training program, and age.

Key components of energy requirements:

1. Basal metabolic rate (BMR): Accounts for 65-70% of daily energy expenditure.
2. Physical activity energy expenditure: Highly variable and increases as training volume and intensity increase.
3. Thermic effect of food: Energy used to digest, absorb, and store 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 many sports may need to reduce body fat to improve performance in speed- and endurance-based events or to meet weight-class requirements. Weight management may also provide a psychological advantage.

Even though there are many diet plans, there isn’t a single “best” diet for all athletes. Research shows that both low-carbohydrate and low-fat diets can work, as long as 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 using 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 can increase satiety and thermogenesis.
• Increased fat oxidation, particularly in active individuals.

However, long-term adherence can be challenging. Athletes should balance carbohydrate intake carefully to avoid declines in training quality and performance.

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.