GLOSSARY

Glucagon Signaling translates receptor activation into cellular responses.

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.

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.

Endogenous glucose production includes glycogen breakdown and new synthesis rather than gluconeogenesis alone. Cellular production and release into blood differ because local use occurs. Contributions change with fasting and activity. Tracers and pool definitions matter; a stable blood glucose can coexist with high turnover. It does not mean fuel is unnecessary or glucose use has stopped, nor does one circulating concentration isolate hepatic versus renal contributions to supply.

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.

When glucose falls, lower insulin secretion and stronger glucose-supporting signals help preserve availability. Glucagon and catecholamines contribute rapidly, while other hormones act over different time scales. Diabetes, medication and prior hypoglycemia can alter the response. Counter-regulatory does not mean harmful: these signals form part of normal defense. Their interpretation depends on context and exercise intensity rather than assuming every rise reflects a disorder or an unfavorable sports response.

Exercise mode, intensity, duration, recruited muscle, training history and prior food influence hormonal responses. Acute changes differ from baseline adaptations after training. Higher concentration does not necessarily mean greater secretion or tissue effect, because clearance, plasma volume and receptors also matter. Performance develops through combined adaptations, so targeting a hormone peak is not sufficient for session design or supplement selection; actual recovery and performance must remain part of evaluation.