CSCS Nutrition Revision Notes: Energy Balance, Macronutrients & Body Composition

Energy Balance and the Macronutrients

Energy balance is the relationship between energy intake and energy expenditure: a sustained caloric surplus supports weight gain, a sustained deficit supports weight loss, and this remains true regardless of macronutrient composition, though composition strongly affects what kind of tissue is gained or lost and how sustainable the approach is. Carbohydrate is the body's preferred and most readily available fuel for moderate-to-high intensity exercise, stored as glycogen in muscle and liver, providing roughly 4 kcal per gram. Protein's primary roles are tissue repair, growth and enzyme/hormone synthesis rather than being a primary fuel source, also providing roughly 4 kcal per gram; general resistance-training athlete protein recommendations commonly fall in the range of 1.4-2.0 g per kg of bodyweight per day, higher than sedentary population guidelines. Fat provides roughly 9 kcal per gram, over double carbohydrate and protein, and is the dominant fuel source at rest and during low-intensity, longer-duration activity, alongside its essential roles in hormone production and fat-soluble vitamin absorption.

Nutrient Timing Around Training

Pre-exercise nutrition generally aims to provide adequate carbohydrate for fuel availability and to avoid gastrointestinal discomfort during the session, typically consumed 1-4 hours beforehand depending on meal size and individual tolerance. Post-exercise nutrition focuses on replenishing glycogen and providing protein to support muscle protein synthesis and recovery; the historical idea of a rigid 30-minute ‘anabolic window’ has been substantially walked back in more recent sports nutrition literature, with total daily protein and carbohydrate intake, and proximity of the pre-workout meal, mattering considerably more than hitting a narrow post-exercise timing target. For CSCS purposes, know both the traditional nutrient timing framework and that total daily intake is now understood to be the primary driver, with meal timing playing a secondary, though still relevant, role.

Hydration and Fluid Balance

Even mild dehydration, a fluid loss of around 2% of bodyweight, is associated with measurable decrements in both physical and cognitive performance. Athletes should begin exercise adequately hydrated, replace fluids during prolonged exercise (particularly sessions beyond 60 minutes or in hot/humid conditions), and rehydrate afterward based on fluid losses, which can be estimated from pre- and post-exercise bodyweight changes. Sports drinks containing carbohydrate and electrolytes offer an advantage over plain water for sessions beyond roughly 60 minutes or involving heavy sweat losses, since they replace lost sodium and provide fuel simultaneously; for shorter or lower-intensity sessions, water alone is generally sufficient. Hyponatraemia, dangerously low blood sodium from excessive plain water intake without adequate electrolyte replacement during very prolonged exercise, is a genuine, testable risk at the opposite extreme from dehydration.

Common Ergogenic Aids and Their Evidence Base

Creatine monohydrate has one of the strongest evidence bases of any legal ergogenic aid, supporting improvements in high-intensity, short-duration, repeated-effort performance by increasing phosphocreatine stores, with typical protocols involving either a loading phase (around 20g/day for 5-7 days) followed by a maintenance dose (around 3-5g/day), or a slower maintenance-dose-only approach without loading. Caffeine improves performance across a range of exercise types via central nervous system stimulation and reduced perceived exertion, typically dosed around 3-6 mg per kg of bodyweight 30-60 minutes pre-exercise. Beta-alanine supports muscular carnosine content, which buffers hydrogen ion accumulation, and is most relevant to sustained high-intensity efforts in the 1-4 minute range where glycolytic by-products are the primary limiter. The exam distinguishes evidence-based, legal ergogenic aids like these from banned substances, and expects you to know the mechanism of action, not just that ‘it helps performance’.

Body Composition Assessment Methods

Skinfold measurement estimates body fat percentage from subcutaneous fat thickness at standardised sites, using population-specific equations; it's practical, inexpensive and widely used in field settings but technician-dependent, requiring consistent site location and technique to be reliable across repeated measurements. Bioelectrical impedance analysis (BIA) estimates body composition from the resistance of an electrical current through body tissue, convenient and non-invasive but sensitive to hydration status, meaning results can shift meaningfully based on fluid intake, exercise timing and even time of day. Hydrostatic (underwater) weighing and air displacement plethysmography (Bod Pod) estimate body composition from body density and are considered more accurate reference methods than skinfolds or BIA, though far less practical for routine field use. DEXA (dual-energy X-ray absorptiometry) provides detailed regional body composition data including bone density and is generally regarded as a gold-standard method, but requires specialised equipment and is the least accessible option in a typical training facility. The exam expects you to match assessment method to context: field-practical vs laboratory-accurate, not just list the methods.

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