INTRODUCTION: Exercise increases insulin stimulated glucose uptake (insulin action) if expended energy (kcal) is withheld following exercise, but the effect is blunted when expended energy is replaced as carbohydrate. Restricting carbohydrate and replacing expended energy as fat maintains increased insulin action in rodents; however, this effect has not been evaluated in humans. In humans, restricting carbohydrate intake following exercise may be a useful strategy to maximize the effect of individual exercise bouts on insulin action and promote gains in metabolic health over time. Therefore, the purpose of this study was to determine if carbohydrate restriction following exercise (carbohydrate deficit) increased insulin action in sedentary, overweight adults as hypothesized. METHODS: Ten healthy, sedentary, men and women, aged 21±2 years, body fat 37.3±3.1%, and VO2peak 34.6±1.2ml×kg-1×min-1 completed three, two-day experimental conditions in random order: 1) a no-exercise baseline condition (BASE), 2) exercise followed by a high-carbohydrate meal (HIGH-CHO= 76.3±2.5% CHO), and 3) exercise followed by a low-carbohydrate meal (LOW-CHO=17.8±0.1% CHO). On DAY 1, subjects came to the laboratory (early evening) and expended 30% of total daily energy expenditure on a cycle ergometer at 70% of VO2peak. Following exercise, an isocaloric meal (HIGH-CHO or LOW-CHO) was consumed to refeed the expended energy during exercise and venous blood samples were taken to record the insulin and glucose responses to the meals. Twelve hours later (Day 2), whole-body insulin action (steady-state glucose uptake per unit insulin) was measured using a continuous infusion of glucose with stable isotope tracers. A paired t-test was used to detect differences between exercise bouts and the glucose and insulin responses to the post-exercise meals. A one-way repeated measures ANOVA was performed to evaluate the effect of experimental condition on insulin action (p<0.05, for all tests). RESULTS: Intensity (VO2peak), duration (minutes) and energy expenditure (kcal) were similar between exercise bouts. After exercise, plasma glucose and insulin concentrations were significantly higher following the HIGH-CHO meal compared to the LOW-CHO meal (p<0.001, respectively). The next morning, insulin action was similar between experimental conditions (p=0.30). Non-oxidative glucose disposal was increased during the glucose infusion in Low-CHO compared to BASE (27.2±3.2 vs. 16.9±3.5µM×kg-1×min-1, p<0.05). Carbohydrate oxidation was reduced in Low-CHO (8.6±1.3µM×kg-1×min-1) compared to High-CHO (12.2±1.2µM×kg-1×min-1), and to BASE (17.1 ± 2.2 µM×kg-1×min-1), p<0.05 respectively. Resting fat oxidation was increased in Low-CHO compared to BASE (109.8 ± 10.5 mg×min-1 vs. 80.7 ± 9.6 mg×min-1, p<0.05) and remained elevated during the glucose infusion. CONCLUSION: Limiting carbohydrate, but not energy intake after exercise (carbohydrate deficit) resulted in increased non-oxidative glucose disposal, decreased carbohydrate oxidation and increased fat oxidation during the glucose infusion, compared to baseline, indicating a favorable shift in energy metabolism. Creating a carbohydrate deficit, by withholding expended carbohydrate but not energy following exercise may be a sensible strategy to promote favorable gains in insulin action that requires further evaluation.

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Ziel dieser vorliegenden, vergleichenden Literaturarbeit ist es, den heutigen Wissensstand in Bezug auf den Kohlenhydratstoffwechsel einer Frau darzustellen. Hierbei werden die physiologischen Veränderungen des Metabolismus zu verschiedenen Zeitpunkten im Leben einer Frau, begonnen mit der Kindheit und Pubertät, über Menstruation und Schwangerschaft bis hin zur Menopause, betrachtet und es werden die Ursachen und möglichen Mechanismen aufgezeigt, die zu Abweichungen der Insulinresistenz und der Insulinsekretion und damit möglicherweise zu einer Glukoseintoleranz bzw. einem Typ-2 Diabetes mellitus führen können. Der Kohlenhydratstoffwechsel wird nicht nur bezüglich der physiologischen, sondern auch in bezug auf die iatrogen verursachten Veränderungen, d.h. unter oraler hormonaler Kontrazeption, unter Hormonersatztherapie im Klimakterium, sowie hinsichtlich bestimmter Pathologien, wie dem zur Infertilität führenden polyzystischem Ovarsyndrom oder dem Gestationsdiabetes, untersucht. Ergebnis: Es scheint eine starke Verknüpfung zwischen dem weiblichen Reproduktionssystem und dem Kohlenhydratstoffwechsel zu geben, deren Interaktion von den unterschiedlichsten Faktoren beeinflusst wird. Der Frauenarzt sollte sich bei der Verschreibung hormoneller Kontrazeptiva, der Hormonersatztherapie und im Besonderen bei der Therapie des polyzystischen Ovarsyndroms sowie bei der Untersuchung seiner Patientinnen bewusst sein, dass verschiedene Lebensphasen, wie Pubertät, Schwangerschaft und Klimakterium und die damit verknüpften Veränderungen des Reproduktionssystems und der Sexualhormone auch deutliche metabolische Veränderungen nach sich ziehen können. Besonders eine erhöhte Insulinresistenz, die mit einer gesteigerten Insulinsekretion einhergeht, muss bedacht werden. Nicht nur das Syndrom X, eine Zusammenfassung von metabolischen Abnormitäten (Dyslipidämie, Insulinresistenz, Adipositas, Hypertonie), die mit einem deutlich erhöhten Risiko kardiovaskulärer Krankheiten und besonders der Atherosklerose einhergehen, sondern die daraus folgende steigende Prävalenz von Typ-2 Diabetes mellitus und das stark vermehrte Auftreten von Adipositas verlangen nach einer fachübergreifenden Zusammenarbeit zwischen Frauenärzten und Internisten. / The aim of this comparative review is to reveal the current standard of knowledge concerning carbohydrate metabolism in women. The study demonstrates the physiological changes in metabolism at various stages in a female life, from childhood and puberty, through menstruation and pregnancy and ending with the menopause, whilst also evaluating different causes and possible mechanisms that lead to aberrance in insulin resistance and insulin secretion and thereby potentially to glucose intolerance and/or type 2 Diabetes mellitus. In addition to presenting physiological alterations in glucose metabolism, this work also analyses changes generated by iatrogenic treatment such as oral contraceptives and hormone replacement therapy, as well as those caused by different pathologies like polycystic ovary syndrome or gestational diabetes. The results indicate a strong correlation between the female reproduction system and the carbohydrate metabolism. The interaction is influenced by the many very different factors. Before prescribing oral contraceptives, hormone replacement therapy in climacteric (especially during the treatment of infertility in PCOS), or examining patients, the gynaecologist needs to be aware of the fact that different phases in life along with sex steroids and connected changes in the reproductive system, might lead to severe metabolic diversifications. Special attention should be paid to an increased insulin resistance, associated with an augmentation in insulin secretion. Not only the metabolic syndrome, the simultaneous appearance of metabolic abnormalities (dyslipidaemia, insulin resistance, adiposity, hypertonia), which holds a higher risk of cardiovascular diseases, especially arteriosclerosis, but also the consequential increased prevalence of type 2 diabetes mellitus and the highly increased prevalence of adiposity, demand for a multidisciplinary collaboration between gynaecologists and internists.