GLOSSARY

Fat-Adapted Athlete describes metabolic adjustment to sustained higher-fat and lower-carbohydrate provision. Increased fat oxidation is one outcome and does not independently establish improved performance.

A sustained low-carbohydrate, high-fat diet can increase reliance on fat and change fuel handling. Nutritional ketosis is a related but more specific state and is not produced by every higher-fat diet. Increased fat oxidation does not establish better performance, particularly when high rates of carbohydrate-supported work are required. Some athlete studies have found impaired exercise economy or high-intensity performance. Restoring carbohydrate after fat adaptation does not guarantee immediate reversal of every effect or the advantages of both approaches.

Fat contributes to exercise energy through circulating fatty acids and intramuscular lipid stores. Greater fat availability, uptake or mobilization does not automatically mean a greater oxidation rate. Relative contribution and absolute rate are also different: the percentage can rise while total exercise demand changes. Oxidizing more fat during one session does not by itself establish greater long-term body-fat loss. Interpret the measured process, exercise intensity, diet and overall energy balance together.

Exercise uses a mixture of fuels whose proportions change with intensity, duration, training and diet. The crossover concept describes a shift toward greater carbohydrate contribution as intensity rises under specified conditions. It is a model of relative fuel use, not an on-off switch that turns fat metabolism off. The crossover point is not fixed across all individuals or protocols. Interpret substrate patterns with the actual workload and available fuel rather than a universal heart-rate zone.

Carbohydrate requirements vary with the intensity, duration and importance of the work. Daily intake relative to body mass describes a different quantity from an intake rate during exercise, which is commonly expressed per hour. A larger daily target does not mean the same amount should be consumed in every session. Match supply to the schedule, starting stores and practical tolerance, and distinguish grams eaten from grams absorbed or oxidized when discussing a fueling plan.

Exercise economy describes oxygen or energy cost at a specified task output, while mechanical efficiency relates external work to metabolic energy input under a stated convention. Gross, net and other efficiency definitions differ in how baseline costs are handled. A lower oxygen cost is not automatically the same as higher maximal aerobic capacity. Compare the same workload, conditions and calculation method, and distinguish a measured physiological change from a demonstrated improvement in race performance.

A nutritional strategy should be evaluated by the quality and relevance of evidence, the athlete's response and the feasibility of implementation. Molecular signaling, a substrate-oxidation change, a laboratory capacity test and race performance are different outcomes. Association does not establish cause, and a response in one small study need not generalize to all athletes. Define the intended benefit before changing the plan, then evaluate training quality, recovery and performance under comparable circumstances rather than judging success by novelty.