Body mass index to predict fat mass and metabolic syndrome severity: should it really be specific to sex, age and ethnicity? A NHANES study (1999-2014).

Background: Body mass index (BMI) is often criticised since it doesn't consider sex, age and ethnicity, which may affect the height scaling exponent of the equation.Aims: First, to identify specific height scaling exponents (α) based on sex, age and ethnicity. Second, to assess the performance of the current vs the proposed BMI equations (1) to predict total fat mass (TFM) and metabolic syndrome (MetS) severity and (2) to correctly identify obese individuals and those having MetS.Methods: In total, 41,403 individuals aged 20-80 years (NHANES, 1999-2014) were studied. Specific "α" were identified using the Benn formula. Various statistical approaches were performed to assess performances of the current vs the proposed-BMIs.Results: The proposed "α" varies from 1.2 to 2.5, after considering sex, age and ethnicity. BMIs calculated using the proposed "α" showed a similar capacity to predict TFM and MetS severity and to correctly identify obese individuals and those having MetS compared to the current BMI.Conclusions: Despite sex, age and ethnicity modulating the height scaling exponent of the BMI equation, using these proposed exponents in the BMI equation didn't improve the capacity to predict TFM and MetS severity, suggesting that the current BMI remains a valid clinical tool.

Long-term exercise training and soy isoflavones to improve quality of life and climacteric symptoms.

OBJECTIVE: To verify the efficacy of phytoestrogen supplementation combined with aerobic and resistance training on the improvement of climacteric symptoms and health-related quality of life (HRQoL) in postmenopausal women. METHODS: From a pool of women who had participated in a 1-year intervention study and were randomly assigned to either exercise + phytoestrogen (EX + PHY) or exercise + placebo (EX + PL), a total of 31 healthy but overweight women (mean age 59.2 ± 4.8 years, body mass index 29.1 ± 3.5 kg/m2) finished the study (EX + PHY, n = 15; EX + PL, n = 16). All the following variables were measured before, after 6 months and after 12 months of intervention: body composition (fat and lean body mass, DXA), HRQoL (SF-36 questionnaire: physical and mental component summaries and subscales; and the 10-item Perceived Stress Scale questionnaire), climacteric symptoms (Kupperman Index questionnaire). RESULTS: After 1 year of intervention, physical functioning (p = 0.003), role-emotional (p = 0.031), vitality (p = 0.007), and global health (p < 0.001) were significantly and similarly increased in both groups. Regarding climacteric symptoms, an improvement in the Kupperman index total score (p = 0.015) was observed. CONCLUSION: Our results demonstrate that adding phytoestrogens to exercise training does not provide the additive effect for HRQoL in postmenopausal and overweight women. Moreover, exercise and phytoestrogen may interfere in the improvement of climacteric symptoms in the long term.

Vasomotor symptoms and cardiometabolic risk factors in menopausal women: a MONET Group study.

INTRODUCTION: Conflicting results have been reported concerning the prevalence of cardiometabolic risk factors in women experiencing vasomotor symptoms (VMS). OBJECTIVES: To compare cardiometabolic risk factors between women with and without VMS during the menopause transition and to determine the influence of physical activity on the prevalence of VMS. METHODS: Yearly assessment of women transitioning through menopause included self-reported VMS (hot flushes and night sweats), body composition and fat distribution, fasting glucose, insulin and lipids, and physical activity levels. RESULTS: Eighty-five of the 102 premenopausal women at baseline were included (age: 49.9 ± 2.0 years; body mass index: 23.2 ± 2.2 kg/m(2)). According to linear mixed model analyses, no statistically significant differences were observed for fat mass, lean body mass, body fat distribution indices and cardiometabolic risk factors, when comparing symptomatic vs. asymptomatic women. Neither physical activity levels nor intensity were associated with the prevalence of VMS. CONCLUSION: Our results suggest that women transitioning through menopause who reported VMS did not show greater deteriorations in body composition, body fat distribution and cardiometabolic risk factors. Furthermore, physical activity levels were not associated with lower prevalence of vasomotor symptoms in the present cohort.

Muscle mass and insulin sensitivity in postmenopausal women after 6-month exercise training.

OBJECTIVE: The common belief that high muscle mass improves insulin sensitivity is controversial and even recent studies have established that larger muscle mass is associated with insulin resistance in sedentary postmenopausal women. Physical activity induces a beneficial effect in muscle size and its metabolic properties. Hence, larger muscle mass induced by exercise training should ameliorate insulin sensitivity and the negative relationship between larger muscle mass and insulin sensitivity should disappear. This study examined the induced changes in muscle mass and insulin sensitivity in postmenopausal women after 6-month exercise training along with their possible correlations. METHODS: Forty-eight sedentary, overweight-to-obese postmenopausal women followed a 6-month mixed exercise training (three sessions/week; endurance and resistance). Lean body mass (LBM) and fat mass (FM) were measured by DXA, then the muscle mass index (MMI) was calculated (MMI = LBM (kg)/height (m(2))). Fasting glucose and insulin measurements were obtained and insulin resistance (IR) was estimated by the HOMA-IR formula. RESULTS: Baseline MMI was correlated with IR (r = 0.219, p = 0.015). After intervention, significant differences were observed in body weight, FM%, MMI, and glycemia, and changes in MMI were significantly correlated with changes in IR (r = 0.345, p = 0.016). Also linear regression showed that the increase in MMI explained 28% of the deterioration in insulin sensitivity (p = 0.001). CONCLUSIONS: After 6 months of mixed training, changes in muscle mass remained correlated with changes in insulin resistance, overweight-to-obese women with large muscle gains being more insulin-resistant. This supports that muscle quality and functionality, and the loss of fat mass, should be targeted rather than muscle mass gains in postmenopausal women, especially in a context of no energy restriction.

Exercise and sleep in aging: emphasis on serotonin.

Reductions in central serotonin activity with aging might be involved in sleep-related disorders in later life. Although the beneficial effects of aerobic exercise on sleep are not new, sleep represents a complex recurring state of unconsciousness involving many lines of transmitters which remains only partly clear despite intense ongoing research. It is known that serotonin released into diencephalon and cerebrum might play a key inhibitory role to help promote sleep, likely through an active inhibition of supraspinal neural networks. Several lines of evidence support the stimulatory effects of exercise on higher serotonergic pathways. Hence, exercise has proved to elicit acute elevations in forebrain serotonin concentrations, an effect that waned upon cessation of exercise. While adequate exercise training might lead to adaptations in higher serotonergic networks (desensitization of forebrain receptors), excessive training has been linked to serious brain serotonergic maladaptations accompanied by insomnia. Dietary supplementation of tryptophan (the only serotonin precursor) is known to stimulate serotonergic activity and promote sleep, whereas acute tryptophan depletion causes deleterious effects on sleep. Regarding sleep-wake regulation, exercise has proved to accelerate resynchronization of the biological clock to new light-dark cycles following imposition of phase shifts in laboratory animals. Noteworthy, the effect of increased serotonergic transmission on wake state appears to be biphasic, i.e. promote wake and thereafter drowsiness. Therefore, it might be possible that acute aerobic exercise would act on sleep by increasing activity of ascending brain serotonergic projections, though additional work is warranted to better understand the implication of serotonin in the exercise-sleep axis.

Soy isoflavones and exercise to improve physical capacity in postmenopausal women.

AIM: In postmenopause, ovarian decline along with sedentary lifestyle could contribute to the loss of lean body mass (LBM) and muscle strength. This study aimed to verify whether exercise and isoflavones could have additive effects on muscle quality, muscle mass index, relative strength and physical capacity in overweight sedentary postmenopausal women. METHOD: We recruited 70 overweight-to-obese (body mass index 32.2±4.8 kg/m(2)) postmenopausal women (59±5 years old) to participate in a 6-month clinical study combining isoflavones (70 mg/day) and exercise (resistance and aerobic training) treatments. Subjects were divided into four groups: (1) placebo (n =15), (2) isoflavones (n =15), (3) exercise and placebo (n =20), and (4) exercise and isoflavone (n =20). Principal outcome variables included maximal muscle strength (1RM) at the leg press and the bench press, muscle mass index, muscle quality in the legs and relative strength. RESULTS: After 6 months of training, exercise produced 49% and 23% increases, respectively, in leg press and bench press 1RM (p ≤0.01). Leg relative strength and muscle quality increased by more than 50% (both p <0.01), while muscle mass index increased by 7% (p <0.05) in both exercise groups only. CONCLUSION: Exercise training can improve muscle tissue strength, function and quality in sedentary postmenopausal women. Isoflavones, irrespective of exercise, did not produce changes in these variables. From a clinical perspective, these results suggest that overweight women could reduce the risks of mobility impairments, even in the absence of weight loss, by following a sound exercise intervention that includes both resistance and aerobic training at a high intensity.

Effect of exercise training and isoflavones on hepatic steatosis in overweight postmenopausal women.

OBJECTIVES: Postmenopausal women are particularly inclined to an increased risk of developing non-alcoholic hepatic steatosis. The purpose of this study was to investigate whether adding isoflavone supplementation to exercise training could reduce the risk. METHODS: In a 6-month, double-blind, randomized, controlled trial, 54 healthy overweight-to-obese (body mass index 28-40 kg/m2) postmenopausal women were randomly assigned to one of the following groups: (1) exercise and isoflavones (Ex-Iso; n = 26), (2) exercise and placebo (Ex-Pla; n = 28). Exercise training consisted of three weekly sessions of mixed training. We examined the plasma level of specific hepatic enzymes (alanine aminotransferase, aspartate aminotransferase, γ-glutamyltransferase, and alkaline phosphatase) as a reflection of fatty liver along with the calculation of the fatty liver index. All measures were obtained at baseline and after the 6-month intervention. RESULTS: Following the intervention, a lower fatty liver index (p <0.01; 29% in Ex-Iso, 18% in Ex-Pla) and plasma γ-glutamyltransferase (p <0.01; 22% in Ex-Iso, 16% in Ex-Pla) were observed in both groups, with a higher reduction in the Ex-Iso group. On the other hand, for all other hepatic enzymes, there was no change. CONCLUSIONS: Our results show that exercise training appears to bring favorable changes in the plasma level of hepatic enzymes, possibly due to the lowering of liver fat content. While postmenopausal women can benefit from this intervention to decrease the risk of developing non-alcoholic hepatic steatosis, it seems that the addition of isoflavones to exercise training provides some additional effects to those provided by exercise alone.

Is a small muscle mass index really detrimental for insulin sensitivity in postmenopausal women of various body composition status?

OBJECTIVES: We sought to determine if a small muscle mass index (MMI) is actually detrimental for insulin sensitivity when studying a large group of postmenopausal women displaying various body composition statuses and when age and visceral fat mass (VFM) are taken into account. METHODS: A cross-sectional study was conducted in 99 healthy postmenopausal women with a BMI of 28±4 kg/m(2). Fat mass and total fat-free mass (FFM) were obtained from DXA and VFM and MMI were estimated respectively by the equation of Bertin and by: Total FFM (kg)/height (m)(2). Fasting plasma insulin and glucose were obtained to calculate QUICKI and HOMA as an insulin sensitivity index. RESULTS: Total MMI and VFM were both significantly inversely correlated with QUICKI and positively with HOMA even when adjusted for VFM. A stepwise linear regression confirmed Total MMI and VFM as independent predictors of HOMA and plasma insulin level. CONCLUSIONS: A small muscle mass might not be detrimental for the maintenance of insulin sensitivity and could even be beneficial in sedentary postmenopausal women. The impact of muscle mass loss on insulin sensitivity in older adults needs to be further investigated.

Effect of exercise combined with phytoestrogens on quality of life in postmenopausal women.

BACKGROUND: Postmenopausal women seem to favor alternative therapies such as exercise and phytoestrogens as a substitute for potentially harmful hormone replacement therapy. Based on previous research, we hypothesized that phytoestrogens combined with exercise could have a synergic effect on women's health. OBJECTIVE: To verify whether phytoestrogens enhance the response to mixed training regarding menopausal symptoms and quality of life in postmenopausal women. METHODS: From a pool of women participating in a 6-month randomized, controlled exercise study, 21 received a placebo (mean age 58.3 ± 5.4 years, body mass index 29.8 ± 5.1 kg/m(2)) and 19 received phytoestrogen supplements (mean age 60.1 ± 3.4 years; body mass index 30.3 ± 4.6 kg/m(2)). Body weight, fat mass and lean body mass (dual-energy X-ray absorptiometry) were assessed. Quality of life was estimated by the Short Form-36 (SF-36) and Perceived Stress Scale-10 (PSS-10) questionnaires, and menopausal symptoms by the Kupperman index. All measurements were performed before and after the intervention. RESULTS: Although the Kupperman index and PSS-10 remained unchanged in both groups, the SF-36 Physical Component Summary and almost all the SF-36 subscales (except for role-emotional and mental health) increased only in the exercise group taking phytoestrogens (0.001 < p < 0.04). CONCLUSION: While phytoestrogens combined with mixed exercise were not sufficient to improve menopausal symptoms, it seemed to be a better strategy than exercise alone to improve the general quality of life in postmenopausal women.

Low-volume walking HIIT: Efficient strategy to improve physical capacity and reduce the risk of cardiovascular disease in older women with type 2 diabetes.

BACKGROUND AND AIMS: To compare the effect of a low-volume walking high-intensity interval training (HIIT) to moderate-intensity continuous training (MICT) on risk of cardiovascular diseases and physical capacity in older women with type 2 diabetes (T2D). METHODS: Thirty inactive older women with T2D were randomized into either HIIT (75 min/week) or MICT (150 min/week). Cardiovascular risk profile (lipid profile; waist circumference and fat mass; resting, post-exercise and ambulatory blood pressure [BP]; VO2 peak; UKPDS score; ABC's) and physical capacity were assessed before and after a 12-week intervention. RESULTS: While resting systolic and diastolic BP (all p ≤ 0.01) were reduced, ambulatory BP (p ≥ 0.49) and lipid profile (p ≥ 0.40) remained unchanged after the intervention. Although VO2 peak increased to a similar extent in both groups (p = 0.015), the distance covered during the 6MWT (p = 0.01) and grip strength (p = 0.02) increased to a greater extend in HIIT. The UKPDS risk score decreased in both groups after the intervention (p = 0.03) and 31% of the participants reached the ABC's compared to 24% at baseline. CONCLUSION: Low-volume walking HIIT is an efficient exercise intervention for older women with T2D as it improved some CVD risk factors and physical capacity. Nevertheless, neither low-volume HIIT nor MICT is sufficient to affect ambulatory blood pressure in T2D patients.

Sarcopenia Prevalence Using Different Definitions in Older Community-Dwelling Canadians.

OBJECTIVES: Sarcopenia is a debilitating condition affecting millions of individuals worldwide and is defined with different criteria. The objective of this study was to determine the prevalence of sarcopenia in older Canadians using three internationally accepted criteria. DESIGN: Observational cohort study. SETTINGS AND PARTICIPANTS: Data from 12,592 subjects [6,314 males (50.1%), 6,278 females (49.9%)] ≥65 years old in the Canadian Longitudinal Study on Aging were included. MEASUREMENTS: Appendicular lean mass (ALM; kg) and appendicular lean mass index (ALM kg/height in m2) were collected from dual X-ray absorptiometry measurements. Physical performance was assessed using the 4-m gait speed test, and muscle strength was measured by hand dynamometry. Sarcopenia was defined according to criteria put forth by the International Working Group on Sarcopenia (IWGS), Foundation for the National Institutes of Health (FNIH) Sarcopenia Project, and revised European Working Group on Sarcopenia in Older People (EWGSOP). Positive and negative percent agreements and Cohen's kappa (κ) described the agreement among sarcopenia definitions. RESULTS: Among the evaluated criteria, gait speed ≤ 1.0 m/s (IWGS definition of slowness) was the most frequently identified deficit (56.8% males, 57.2% females). The prevalence of sarcopenia ranged from 1.4 to 5.2% in males and 1.6 to 7.2 % in females among the different definitions. Positive percent agreement values among criteria were generally low (range: 1.5 - 55.3%) and corresponded to κ indicating none to minimal agreement (0.01 - 0.23). Negative percent agreement values were ≥ 95%. CONCLUSION: Sarcopenia prevalence was relatively low in older Canadian adults and current definitions had poor agreement in diagnosing individuals as sarcopenic.

Effect of antioxidants combined to resistance training on BMD in elderly women: a pilot study.

SUMMARY: We determined the effect of antioxidants and resistance training on bone mineral density of postmenopausal women. After 6 months, we observed a significant decrease in the lumbar spine BMD of the placebo group while other groups remained stable. Antioxidants may offer protection against bone loss such as resistance training. INTRODUCTION: The purpose of this pilot study was to determine the effects of antioxidant supplements combined to resistance training on bone mineral density (BMD) in healthy elderly women. METHODS: Thirty-four postmenopausal women (66.1 +/- 3.3 years) were randomized in four groups (placebo, n = 7; antioxidants, n = 8; exercise and placebo, n = 11; and exercise and antioxidants, n = 8). The 6-month intervention consisted in antioxidant supplements (600 mg vitamin E and 1,000 mg vitamin C daily) or resistance exercise (3x/week). Femoral neck and lumbar spine BMD (DXA) and dietary intakes (3-day food record) were measured before and after the intervention. A repeated measure ANOVA and non-parametric Mann-Whitney U tests were used. RESULTS: We observed a significant decrease in the placebo group for lumbar spine BMD (pre, 1.01 +/- 0.17 g/cm(2); post, 1.00 +/- 0.16 g/cm(2); P < 0.05 respectively) while it remained stable in all other groups. No changes were observed for femoral neck BMD. CONCLUSIONS: Antioxidant vitamins may offer some protection against bone loss in the same extent as resistance exercise although combining both does not seem to produce additional effects. Our results suggest to further investigate the impact of antioxidant supplements on the prevention of osteoporosis.

Changes in muscle mass and strength after menopause.

Menopause is associated with a natural decline in estrogen, that increases visceral fat mass, decreases bone mass density, muscle mass, and strength. This review will examine the role of menopause transition and associated decrease in hormonal status with regards to those changes. We will also overview the efficiency of physical exercise and nutrition on muscle subcharacteristics. Studying changes in muscle mass associated with menopause is important, because of the high number of postmenopausal women in developed countries and the related risk of physical incapacity. Among modifiable factors, low physical activity and protein intakes are the best contributors to sarcopenia and the loss of strength in postmenopausal women. On the other hand, some biological factors, namely oxidative stress, inflammation, estrogen and other hormone deficiency are predictors of these phenomena. Interestingly, some methods have the potential to attenuate the loss of muscle mass and strength such as exercise, and supplement intake.

Six months of isoflavone supplement increases fat-free mass in obese-sarcopenic postmenopausal women: a randomized double-blind controlled trial.

OBJECTIVE: The aim of this study was to verify if six months of isoflavone supplementation could increase fat-free mass (FFM) and muscle mass index (MMI=appendicular FFM/height(2)) in obese-sarcopenic postmenopausal women. DESIGN: Double-blind randomized study. SUBJECT: Eighteen sarcopenic-obese women completed the study (12 on isoflavones and six on placebo). Body composition was measured by dual-energy X-ray absorptiometry. Subjects ingested 70 mg of isoflavones per day (44 mg of diadzein, 16 mg glycitein and 10 mg genestein) or a placebo for 24 weeks. RESULTS: The isoflavone group increased significantly appendicular (P=0.034), leg (P=0.016) FFM and MMI (P=0.037), but not the placebo group. CONCLUSION: Six months of isoflavone supplementation increased FFM and MMI in obese-sarcopenic postmenopausal women.

Dietary animal protein intake: association with muscle mass index in older women.

BACKGROUND: Aging is associated with reductions in muscle mass and strength, so-called sarcopenia, and is generally characterized using muscle mass index (MMI = FFM (kg)/height (m)2). It is believed that adequate nutrition especially regarding protein intake, can delay this progression and enhance the quality of life of elders. OBJECTIVES: We examined whether the predominant source of protein consumed (animal or vegetal) by older women was associated with MMI. DESIGN: Thirty-eight healthy, normal weight, sedentary women, aged between 57-75 years (mean age: 66 +/- 5 years old), and taking no medication that could influence metabolism were recruited. Body composition was measured by dual-energy X-ray absorptiometry; muscle protein content was measured by the use of creatinine excretion. Physical activity metabolism was obtained by the use of accelerometry, and indirect calorimetry. Finally, protein intake was measured with a 3-day dietary record. RESULTS: Significant correlations were observed between MMI and body mass index, fat-free mass, muscle protein content, total protein intake, animal protein intake, fat mass, visceral fat and daily energy expenditure. However, a stepwise regression analysis showed animal protein intake to be the only independent predictor of MMI (r2=0.19; p=0.008). CONCLUSIONS: Our results suggest that protein intake, especially from animal sources, may be associated with a better preservation of MMI. However, more research is needed to confirm our results.

Relationship between antioxidant intakes and class I sarcopenia in elderly men and women.

BACKGROUND: The effect of nutritional intake on sarcopenia has been mostly examined in class II sarcopenia, i.e. when muscle mass has sufficiently decreased to induce a loss in physical capacity. Although this provides important information regarding the treatment of sarcopenia, it may not help highlight mechanisms involved at the very beginning of its development. HYPOTHESIS: We hypothesized that class I sarcopenia is associated with differences in antioxidant intakes (vitamins A, C, E and selenium) and status in healthy, older white men and women when physical activity and protein intake are taken into account. DESIGN: Fat-free mass and total appendicular skeletal muscle mass was determined by dual-energy X-ray absorptiometry in 50 healthy, older white men (n = 16) and women (n = 34) aged 60-75 yrs. Physical activity energy expenditure (PAEE) was determined using a Caltrac accelerometer over a 3-d period. Dietary protein and antioxidant intakes were estimated from a 3-d food record and serum total antioxidant activity (TAA) was measured by a ferrylmyoglobin- ABTS assay. RESULTS: The prevalence of class I sarcopenia was 23.5 % in women and 25.0 % in men; 12 participants were thus considered sarcopenic (4 men and 8 women) and 38 participants were considered nonsarcopenic (12 men and 26 women). Our results showed that PAEE, serum albumin concentrations, TAA, and the four antioxidants intake levels were similar between groups. On the other hand, our results showed that total protein intake was significantly higher (P < 0.01) in the non-sarcopenic group than in the sarcopenic group. Also, the number of Recommended Dietary Allowances (RDAs) reached for the antioxidant nutrients and protein intakes by the non-sarcopenic group was significantly higher (P < 0.01) than in the sarcopenic group. CONCLUSIONS: Although there were no significant differences between the sarcopenic and the non-sarcopenic group when antioxidant intakes were considered individually, we observed that the number of RDAs reached for antioxidant micronutrients and protein in healthy, older white men and women was lower in sarcopenic than nonsarcopenic individuals. Our results also suggest that a higher total dietary protein intake is associated with the preservation of muscle mass loss although both groups displayed values above actual RDAs. Obviously, prospective studies are needed to determine the minimum amount of protein in the diet needed to prevent class I sarcopenia and to examine the utility of antioxidant intake to combat the age-related loss in skeletal muscle mass.

Effect of a High-Protein Energy-Restricted Diet Combined with Resistance Training on Metabolic Profile in Older Individuals with Metabolic Impairments.

Adequate protein intake and resistance training are effective strategies to maintain muscle mass, but the effect of their combination on metabolic profile during weight loss remains to be determined in older adults. The main objective of this study was to determine the effect of a 16-week high-protein caloric restriction combined with resistance training on chronic disease risk factors in obese older individuals with metabolic impairments. A total of 26 overweight adults aged between 60 and 75 years (BMI 32.4 ± 3.9 kg/m2) with at least 2 factors of the metabolic syndrome participated in this study and were randomized into two groups: 1) high-protein caloric restriction (HP; n= 12) and 2) high-protein caloric restriction combined with dynamic-resistance training (HP+RT; n=14). Caloric intake was reduced by 500 kcal/d in all participants and protein intake equated 25-30% of total calories (~1.4 g/kg/d). Exercise training consisted of 3 session/week of resistance training on pulley machines. Outcome measures included total and trunk fat mass (FM), total and appendicular lean body mass (LBM), fasting glucose level, lipid profile and blood pressure. Our results showed that total and trunk FM (all p<0.0001) as well as fasting glucose (p<0.0001), triglycerides (p=0.002) and total cholesterol (p=0.03) levels decreased similarly in both groups. However, total (p=0.04) and appendicular (p=0.02) LBM decreased in the HP group only. Our data show that high-protein energy restriction improves health profile of obese elderly at high risk of chronic disease but needs to be combined with resistance training to maintain LBM.

Muscle Mass Index and Animal Source of Dietary Protein Are Positively Associated with Insulin Resistance in Participants of the NuAge Study.

OBJECTIVES: Contribute evidence towards the complex interrelationships of body composition, insulin sensitivity and protein intake independently from adiposity in an older population. DESIGN: This is a cross-sectional analysis of an existing dataset in which a literature-supported model linking together the variables of interest is tested using path analysis. SETTING: The loss of muscle mass has been implicated in the development of insulin resistance. We propose to test associations of muscle mass with insulin sensitivity and their respective associations with animal and vegetable sources of protein intake, independently from adiposity. PARTICIPANTS: Non-diabetic participants aged 68-82 years from the NuAge study with all available measures (n=441) were included. MEASUREMENTS: A model considering age, sex, chronic diseases, physical activity; smoking and sources of protein intake influencing body composition components and insulin sensitivity was created and tested with Path Analysis for their independent associations. Muscle mass index (MMI; kg/height in m2) and % body fat were derived from DXA and BIA. Insulin resistance was estimated by the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) score and physical activity by the Physical Activity Scale for the Elderly (PASE) questionnaire. Protein intakes were obtained from three non-consecutive 24h-diet recalls. RESULTS: In the final model, direct positive associations were observed between HOMA-IR score and MMI (ß=0.42; 95%CI: 0.24; 0.6) and % body fat (ß=0.094; 95%CI: 0.07; 0.11). There were no direct associations between animal protein intake and MMI or with HOMA-IR. There was a significant direct negative association between plant protein intake and MMI (ß= -0.068; 95%CI: -0.13; -0.003) and significant indirect associations mediated through MMI and % body fat between HOMA-IR and animal protein intake (ß=0.0321; 95%CI: 0.01; 0.05), as well as plant protein intake (ß= -0.07; 95%CI: -0.1; 0.0). CONCLUSIONS: Our final model indicated that MMI and HOMA score were significantly positively associated. Protein intake sources were related to HOMA-IR score differently through MMI and % body fat, respectively.

Identification of an interactive effect of beta3- and alpha2b-adrenoceptor gene polymorphisms on fat mass in Caucasian women.

Several adrenoceptor subtypes are expressed in adipocytes, which together exert their influence on adipocyte metabolism. Therefore, we specifically examined the interactive effect of Trp64Arg (beta3) and Glu12/Glu9 (alpha2b) adrenoceptor (AR) polymorphisms on energy metabolism and body composition in healthy women with a wide range of body habitus. We genotyped 909 unrelated women (age 55 +/- 12 [mean +/- SD] years, range 19-87; body weight 88 +/- 22 kg, range 40-167; and BMI 33 +/- 8 kg/m2, range 16-64) for Trp64Arg beta3AR and Glu12/Glu9 alpha2bAR variants. We examined the independent effect of the Glu12/Glu9 alpha2bAR variant on body composition and energy balance, in a large cohort of Caucasian women (n = 909). A second goal was to examine the interaction effect of Glu12/Glu9 alpha2bAR and Trp64Arg beta3AR on the same phenotypes. The obesity-related phenotypes studied were as follows: body weight, BMI, fat mass, visceral fat, fat-free mass, resting metabolic rate (RMR), VO2max, leisure time physical activity, and daily energy intake. Body composition and body fat distribution were measured by dual-energy X-ray absorptiometry and radiographic imagery, VO2max by a treadmill test to exhaustion, and RMR by indirect calorimetry. An analysis of covariance indicated that in the entire cohort, there was no significant difference between Glu12/Glu9 alpha2bAR carriers and control subjects for any of the obesity-related phenotypes that were examined. However, we observed a significant interaction effect of the Trp64Arg and Glu12/Glu9 variants on fat mass (P = 0.009) and percent fat (P = 0.016). Age, height, body weight, BMI, fat-free mass, visceral fat, energy expenditure, respiratory quotient, physical fitness, and energy intake were not different among groups. Collectively, these findings support an interaction effect of the two adrenoceptor variants on body fatness in Caucasian women, although the physiological mechanism by which they exert this effect remains to be determined.

Contribution of abdominal adiposity to age-related differences in insulin sensitivity and plasma lipids in healthy nonobese women.

OBJECTIVE: We examined the hypothesis that an age-related increase in the compartments of visceral fat would account, in part, for the deleterious changes in insulin sensitivity and blood lipid profile in nonobese women. RESEARCH DESIGN AND METHODS: We directly assessed visceral and subcutaneous abdominal adipose tissue areas (computed tomography), glucose disposal (hyperinsulinemic-euglycemic clamp), body composition (dual energy X-ray absorptiometry), blood-lipid profile, and aerobic fitness (VO2max) in 178 nonobese women categorized into four age groups: group 1, 28 +/- 4 years, n = 88; group 2, 46 +/- 2 years, n = 38; group 3, 53 +/- 2 years, n = 31; and group 4. 67 +/- 6 years, n = 21. RESULTS: Visceral abdominal adipose tissue area increased with age (2.36 cm2 per year, P < 0.0001). We noted an age-related increase in total cholesterol (P < 0.0003), triglycerides (P < 0.0009), LDL cholesterol (P < 0.027), and the ratio of total cholesterol to HDL cholesterol (P < 0.042). However, age-related changes in insulin sensitivity exhibited a different age-related pattern. That is, insulin sensitivity, expressed on an absolute basis or indexed per kilogram of fat-free mass, was lowest in group 4 but was not significantly different among groups 1, 2, and 3. After statistical control for visceral fat, lower insulin sensitivity persisted in group 4, although differences were diminished relative to other groups. However, the effect of visceral fat on age-related changes in the blood-lipid profile was stronger. That is, differences in visceral and deep subcutaneous adipose tissue area abolished age-related differences in total cholesterol, triglycerides, and LDL cholesterol. No independent effects of VO2max or leisure-time physical activity on age-related changes in insulin sensitivity or on the blood-lipid profile were noted. CONCLUSIONS: We conclude that 1) visceral fat shows an increase with advancing age, whereas a decrease in insulin sensitivity was noted only in older women; 2) age-related differences in visceral fat explain only a modest part of the decline in insulin sensitivity in nonobese women; and 3) unfavorable changes in plasma lipids were strongly associated with the age-related increase in visceral abdominal adipose tissue.