GLOSSARY

PI3K–Akt Pathway is an important branch of insulin and growth signaling.

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.

Muscle contraction can increase GLUT4 trafficking and glucose uptake through partly insulin-independent routes. Circulating insulin may decline during activity while muscle glucose use rises, so lower insulin does not universally imply lower glucose use. Recovery can also change sensitivity. Exercise type, surrounding meals and glucose-lowering medication alter interpretation; physiological changes in healthy exercise should not be transferred directly to medication management or disease without individualized clinical context.

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.

Whole-body, liver, muscle and adipose insulin sensitivity are not one interchangeable measurement. Suppression of glucose production matters in liver, stimulation of uptake in muscle and suppression of lipolysis in adipose tissue. Resistance can differ between tissues and coexist with compensatory secretion. One fasting test without method and context cannot map the entire condition, and a postexercise change is not automatically evidence of disease or a need to eliminate carbohydrate.

Proinsulin processing produces insulin and C-peptide. C-peptide helps assess endogenous secretion but has different clearance from insulin, so concentrations and ratios need clinical context. Early and sustained secretion phases depend on stimulus and test method. One value cannot establish total beta-cell reserve, sensitivity across every tissue or medication need. Interpretation must distinguish secretion, precursor processing and removal rather than treating their biomarkers as identical measurements.

Blood glucose reflects food entry, endogenous production and tissue removal under coordinated insulin, glucagon and other neural and hormonal signals. A transient meal response is not the same as persistent impaired glucose tolerance; sampling method and timing matter. Measuring glucose is not directly measuring all energy available to muscle. Glycogen, exercise intensity and other fuels also enter sports interpretation, so one curve cannot by itself rate every meal or establish a diagnosis.

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.