Diet, energy and performance
Physical Education · GCSE · The School
The groups
CARBOHYDRATE is the main energy source for exercise. PROTEIN builds and repairs tissue. FAT is a concentrated energy store and carries some vitamins. VITAMINS and MINERALS enable body processes — iron for oxygen transport, calcium for bone. FIBRE aids digestion. WATER is required for nearly everything.
Hydration
Even 2% dehydration measurably reduces performance and concentration before you feel notably thirsty — thirst is a late signal, not an early one. In endurance events, losing salts matters as well as losing water, which is what electrolyte drinks address. Drinking far too much plain water is also dangerous, which is a genuinely counter-intuitive point.
Diet and the sport
An endurance athlete emphasises carbohydrate to fuel long efforts. A strength athlete emphasises protein for repair and growth. Timing matters too: carbohydrate before, protein and carbohydrate after. Answering 'eat healthily' earns nothing; naming the nutrient, the reason and the sport earns the marks.
A MARATHON RUNNER the night before a race: high carbohydrate — pasta, rice, bread — to fill glycogen stores, moderate protein, low fat and fibre so digestion is easy. A SPRINTER or weightlifter in training: adequate carbohydrate for the session, and protein spread across the day for repair and adaptation. Same nutrient groups, very different proportions, because the events demand energy over different timescales.
Energy balance, and why it is the whole answer
Most diet questions reduce to energy in against energy out. Energy in is what is eaten; energy out is basal metabolic rate plus the energy cost of activity. A balance means weight is maintained, a surplus means it is gained, a deficit means it is lost. This one frame answers questions about a marathon runner, a sumo wrestler and a sedentary adult without learning three separate accounts. Say which way the balance tips and what that means for the performer in their specific sport, rather than describing food groups again — the groups are recall, and the balance is the analysis.
Timing, not just content
The exam expects you to know that WHEN food is eaten matters as much as what. A large meal shortly before competition diverts blood to the digestive system and commonly causes discomfort, so it is usually taken two to four hours before. Carbohydrate loading in the days before an endurance event raises glycogen stores. After exercise there is a window in which refuelling and rehydrating are most effective, and protein supports the repair of the muscle damage training caused. Answers that describe an athlete's diet without ever mentioning timing are missing an easy band of marks.