Effects of exercise and dietary intervention on metabolic syndrome markers of inactive premenopausal women

Abstract

The effects of exercise and dietary intervention on metabolic syndrome (Mets) markers of inactive premenopausal women were investigated. In Study I, early markers of MetS were examined in young, (21.2 ± 0.3 years), healthy but unfit women (N = 66) consuming a processed food diet. A second aim was to examine the relationship between ethnic influences (European versus Chinese) and early markers of MetS (e.g., hyperinsulinemia). Study II compared the hormonal and metabolic responses to steady state exercise (SSE) and high intensity interval exercise (HIIE) in untrained young women (N = 18, 21.7 ± 0.8 years). Women were further divided into high and low fasting insulin levels to determine if hyperinsulinemia influenced hormonal and metabolic response to SSE and HIIE. Study III examined the hormonal and metabolic response to a randomized controlled intervention named the Fish oil, Exercise and Mediterranean diet (FEM) trial. The FEM trial was conducted with overweight, inactive young (23.5 ± 0.6 years) women (N = 56) for 12 weeks. Characteristics of a subset of women (N = 34, 23.5 ± 0.7 years) in the FEM trial, non-responders (NRES), who did not lose weight (≤ 1% loss in mass), were also examined. Metabolic profiles were developed based on body composition, aerobic fitness, blood markers, diet, resting metabolic rate, medical history, blood pressure, and autonomic function. Body composition was measured by skinfolds and girths, bioimpedance (Tanita, Japan), and Dual Energy X-Ray Absorptiometry. Peak oxygen uptake was assessed using an open circuit spirometer, TrueMax 2400 Metabolic Cart. Venepuncture and cannulation techniques were used for collecting blood samples that were also centrifuged and frozen for later analysis. In Study I young women who were physically unfit and consumed a processed food diet possessed high levels of fasting insulin, HOMA-IR (an insulin resistance index), and C-reactive protein (CRP). Insulin, p < .001, and HOMA-IR, p < .05, were significantly greater in Chinese Australians compared to European Australians, whereas plasma CRP levels were significantly, p < .05, lower. Significant differences, p < .05, existed between the groups with the Chinese Australians possessing lower body composition indices. However, ethnic differences still existed for insulin, HOMA-IR, and CRP after adjusting for body composition. Both groups consumed significantly high protein relative to their body mass. Thus, it appears that hyperinsulinemia is one of the earliest markers of MetS in young inactive females of both European and Asian descent who are unfit and consume a high level of dietary protein. In Study II, HIIE compared to SSE proved to be more effective at preventing an increase in insulin levels in the two hours after exercise. Resting respiratory quotient (RQ) was significantly lower, p < .05, following both HIIE and SSE, whereas plasma glycerol levels were higher, p = .06, suggesting greater lipolysis following HIIE. The women were divided by baseline fasting plasma insulin (> 9.98 µIU/ml) into high insulin (HI) and low insulin groups (LI). The fasting plasma human growth hormone levels of the HI women were significantly lower at baseline compared to that of LI women. Baseline RQ was correlated with baseline glycerol, r = - .54, p < .05. Insulin levels at one hour post HIIE was related to fasting plasma adrenocorticotropic hormone (ACTH) one hour post exercise, r = .52, p < .05. Fasting plasma leptin at one, r = .56, p < .05, and two, r = .53, p < .05, hours post exercise was associated with 2 hour post insulin levels. Interestingly, fasting ACTH was significantly elevated in the 2 hours post exercise in the HI women compared to LI. All diet data between the groups were similar and lipids were in the healthy range with no significant differences between the women possessing high or low fasting plasma insulin. Thus, young women who completed one session of short duration HIIE compared to SSE improved certain aspects of their metabolic profile (e.g., reduced insulin levels) and enhanced their fat oxidation in the immediate two-hour exercise recovery period. Following FEM (a 12-week multi-component lifestyle intervention) overweight women recorded significantly lower, p < .05, body composition (mass, fat mass, percent body fat, waist circumference), insulin, inflammation (CRP), blood pressure, and lipids. The improvements within the Mediterranean diet (Mediet) were related to the reductions in body weight, fat mass, and insulin. Consumption of saturated fats, legumes, meat, poultry, and egg were also significantly decreased, p < .05, following the trial. Adherence to the Mediet and fish oil consumption, measured through a Mediet score, was significantly increased, p < .001, and was associated with reduced levels of fat mass, r = .43, p < .05. Autonomic function (measured by power frequency analysis), aerobic fitness, and fat oxidation were all significantly, p < .05, enhanced. Therefore, an intervention incorporating fish oil consumption, HIIE, and Mediet significantly reduced body fat, fasting insulin, inflammatory markers, and some blood lipids. Interestingly, some women did not lose fat mass following the FEM intervention, despite experiencing significant reductions in insulin, inflammation, waist circumference, blood pressure, and an increase in aerobic power. The major differences between those women who lost fat and those that did not was that the non-responders possessed significantly lower, p < .05, systolic blood pressure, lower resting heart rate, and a higher resting RQ. In summary, in Study I, young, unfit women consuming a processed diet, demonstrated hyperinsulinemia and low grade inflammation. The high levels of fasting insulin suggest that these women are at a higher risk for developing MetS and type 2 diabetes. The results of Study II suggests that one bout of HIIE compared to a longer bout of SSE was more effective at preventing a rise in post-exercise insulin levels. Finally, results of Study III indicate that a 12-week lifestyle intervention, encompassing HIIE, fish oil ingestion, and a Mediet positively influenced early MetS markers (e.g., hyperinsulinemia), aerobic and anaerobic fitness, low grade inflammation, and body composition in young women.