GLOSSARY

Fasting Hormonal Response is the duration- and context-dependent response to food absence.

Meals change uptake, storage, use and hormones; postabsorptive periods increase reliance on stores and endogenous supply. The transition is not an exact clock switch identical for every meal. Mixed foods and recent exercise alter patterns. Athletes should consider session goals, total daily adequacy and tolerance rather than assuming fasted or fed conditions are superior for every outcome. An acute metabolic shift does not directly establish long-term body composition or training benefit.

Overnight fasting differs from prolonged severe starvation. As restriction continues, glycogen, gluconeogenesis, fat and ketone contributions shift without eliminating all glucose and protein needs. Survival adaptation is not automatically optimal sports preparation. Severe prolonged undernutrition can also require supervised nutritional restoration, unlike ordinary pre- and post-exercise meal planning. Interpret duration and energy context rather than treating every fast as the same metabolic condition or a guaranteed route to better performance.

Insulin is secreted by pancreatic beta cells and coordinates nutrient use and storage rather than simply being a fat-making hormone. Important effects include muscle and adipose glucose uptake, suppression of hepatic glucose production and regulation of lipolysis. Not every cell needs insulin for glucose entry. Postmeal concentrations vary with meal composition, tissue sensitivity and clearance, so one insulin excursion cannot determine overall dietary quality or an athlete's nutritional needs.

Glucagon is mainly secreted by alpha cells and supports glucose availability, prominently through the liver. Its response is not simply the inverse of insulin: amino acids and meal type matter, and both can rise after protein. Direct skeletal-muscle effects should not be assumed equivalent to hepatic effects. Their ratio is context-dependent rather than a food-quality score, and changes need secretion, clearance and tissue actions considered together.

For practical use, record meal and training timing, sleep and hunger alongside actual intake and performance trends. When a marker changes, first examine measurement conditions and plausible explanations; food decisions should support adequate supply, tolerance and recovery rather than ending the assessment at one molecular signal or assuming a concentration change automatically establishes a useful intervention.

Carbohydrate, protein and fat have different digestive and signaling routes that interact in mixed meals. Protein can stimulate both insulin and glucagon; insulin is not simply an added-sugar marker. Fat and fiber can shift timing through gastric-emptying effects. Program quality depends on energy, nutrients, tolerance and fit with training rather than producing the lowest possible hormonal response after every meal or treating physiological insulin secretion as inherently undesirable.

Low energy availability means insufficient energy remains after exercise for required bodily functions; it is not synonymous with low carbohydrate or weight loss alone. Problematic exposure can affect reproductive, thyroid, bone and appetite systems with variable patterns. Restoring supply and reviewing training load are central to assessment. One normal hormone or a universal numerical cutoff cannot confirm or exclude every case, so symptoms, history and clinical evaluation must be integrated.