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Biomedical subjects

Susan B Racette

Publications and source records attributed to Susan B Racette.

18 recordsLinked to original sources
PubMed2006

Lower extremity muscle size and strength and aerobic capacity decrease with caloric restriction but not with exercise-induced weight loss.

Caloric restriction (CR) results in fat loss; however, it may also result in loss of muscle and thereby reduce strength and aerobic capacity (VO2 max). These effects may not occur with exercise-induced weight loss (EX) because of the anabolic effects of exercise on heart and skeletal muscle. We tested the hypothesis that CR reduces muscle size and strength and VO2 max, whereas EX preserves or improves these parameters. Healthy 50- to 60-yr-old men and women (body mass index of 23.5-29.9 kg/m2) were studied before and after 12 mo of weight loss by CR (n = 18) or EX (n = 16). Lean mass was assessed by dual-energy X-ray absorptiometry, thigh muscle volume by MRI, isometric and isokinetic knee flexor strength by dynamometry, and treadmill VO2 max by indirect calorimetry. Both interventions caused significant decreases in body weight (CR: -10.7 +/- 1.4%, EX: -9.5 +/- 1.5%) and lean mass (CR: -3.5 +/- 0.7%, EX: -2.2 +/- 0.8%), with no significant differences between groups. Significant decreases in thigh muscle volume (-6.9 +/- 0.8%) and composite knee flexion strength (-7.2 +/- 3%) occurred in the CR group only. Absolute VO2 max decreased significantly in the CR group (-6.8 +/- 2.3%), whereas the EX group had significant increases in both absolute (+15.5 +/- 2.4%) and relative (+28.3 +/- 3.0%) VO2 max. These data provide evidence that muscle mass and absolute physical work capacity decrease in response to 12 mo of CR but not in response to a similar weight loss induced by exercise. These findings suggest that, during EX, the body adapts to maintain or even enhance physical performance capacity.

Adaptation, Physiological↗
PubMed2006

Improvements in glucose tolerance and insulin action induced by increasing energy expenditure or decreasing energy intake: a randomized controlled trial.

BACKGROUND: Weight loss, through calorie restriction or increases in energy expenditure via exercise, improves glucose tolerance and insulin action. However, exercise-induced energy expenditure may further improve glucoregulation through mechanisms independent of weight loss. OBJECTIVE: The objective was to assess the hypothesis that weight loss through exercise-induced energy expenditure improves glucoregulation and circulating factors involved in insulin action to a greater extent than does similar weight loss through calorie restriction. DESIGN: Sedentary men and women aged 50-60 y with a body mass index (kg/m(2)) of 23.5-29.9 were randomly assigned to 1 of 2 weight-loss interventions [12 mo of exercise training (EX group; n = 18) or calorie restriction (CR group; n = 18)] or to a healthy lifestyle (HL) control group (n = 10). The insulin sensitivity index and areas under the curve for glucose and insulin were assessed with an oral-glucose-tolerance test. Adiponectin and tumor necrosis factor alpha concentrations were measured in fasting serum. Fat mass was measured by dual-energy X-ray absorptiometry. RESULTS: Yearlong energy deficits were not significantly different between the EX and CR groups, as evidenced by body weight and fat mass changes. The insulin sensitivity index increased and the glucose and insulin areas under the curve decreased in the EX and CR groups, remained unchanged in the HL group, and did not differ significantly between the EX and CR groups. Marginally significant increases in adiponectin and decreases in the ratio of tumor necrosis factor alpha to adiponectin occurred in the EX and CR groups but not in the HL group. CONCLUSIONS: Weight loss induced by exercise training or calorie restriction improves glucose tolerance and insulin action in nonobese, healthy, middle-aged men and women. However, it does not appear that exercise training-induced weight loss results in greater improvements than those that result from calorie restriction alone.

Adiponectin↗
PubMed2006

One year of caloric restriction in humans: feasibility and effects on body composition and abdominal adipose tissue.

BACKGROUND: Caloric restriction (CR) increases maximal life span in short-lived organisms, and its effects are being explored in nonhuman primates. The objectives of this study were to determine the feasibility of prolonged CR in nonobese adults and to compare the effects of CR- and exercise-induced weight loss on body composition and abdominal adiposity. METHODS: A randomized, controlled trial was conducted with 48 healthy, nonobese women and men, aged 57 +/- 1 (mean +/- standard error [SE]) years, with body mass index 27.3 +/- 0.3 kg/m2. Participants were randomly assigned to a 20% calorically-restricted diet (CR, n = 19), exercise designed to produce a similar energy deficit (EX, n = 19), or a healthy lifestyle control group (HL, n = 10) for 1 year. Assessments included weight, body composition by dual-energy x-ray absorptiometry, abdominal adipose tissue by magnetic resonance imaging, and energy intake by doubly labeled water. RESULTS: The average level of CR achieved by the CR group was 11.5 +/- 2.1%, and the EX group completed 59 +/- 6.7% of their prescribed exercise. Weight changes were greater (p <or=.0005) in the CR (-8.0 +/- 0.9 kg) and EX (-6.4 +/- 0.9) groups as compared to the HL group (-1.3 +/- 0.9 kg), corresponding to reductions of 10.7%, 8.4%, and 1.7% of baseline weights, respectively. Whole-body fat mass and visceral and subcutaneous abdominal adipose tissue decreased significantly (p <.005) and comparably in the CR and EX groups, but did not change in the HL group. CONCLUSIONS: CR for 1 year was feasible, but the level of CR achieved was less than prescribed. CR and exercise were equally effective in reducing weight and adiposity.

Abdominal Fat↗
PubMed2006

Abdominal adiposity is a stronger predictor of insulin resistance than fitness among 50-95 year olds.

OBJECTIVE: Physical inactivity and increased adiposity contribute to insulin resistance; less is known, however, about the relative contributions of these factors in older adults. The aim of this study was to determine whether cardiovascular fitness, whole-body adiposity, or abdominal adiposity is the strongest predictor of insulin resistance into old age. RESEARCH DESIGN AND METHODS: Subjects included 407 men and women aged 50-95 years (means +/- SD 69 +/- 11 years). Insulin resistance was estimated using the insulin sensitivity index (ISI) of Matsuda and DeFronzo [ISI = 10,000/square root of (fasting glucose x fasting insulin) x (mean glucose x mean insulin during an oral glucose tolerance test); lower ISI = greater insulin resistance]. Fitness was determined with a treadmill maximal oxygen consumption (Vo(2max)) test. Whole-body adiposity measures included BMI and percent fat by dual-energy X-ray absorptiometry or hydrodensitometry; abdominal adiposity was estimated by waist circumference. RESULTS: Waist circumference was the strongest independent correlate of ISI (r = -0.52, P < 0.0001), explaining 28% of the variance when controlling for sex, BMI, percent fat, and Vo(2max). BMI (r = -0.45), percent fat (r = -0.40), and Vo(2max) (r = 0.22) independently predicted ISI (all P < 0.0001); however, after controlling for waist circumference, only Vo(2max) remained significant (r = 0.13, P = 0.009). CONCLUSIONS: Adiposity and fitness continue to be significant predictors of insulin sensitivity into old age, with abdominal obesity being the most important single factor. These findings support the measurement of waist circumference to assess health risk among older adults.

Abdominal Fat↗
PubMed2005

Modest weight loss improves insulin action in obese African Americans.

OBJECTIVE: We have previously shown that short-term energy restriction followed by modest lifestyle changes improves glucose tolerance for up to 1 year in obese individuals. The purpose of the present study was to determine the mechanism by which improvements in glucose tolerance occur in obese African Americans with insulin resistance and abnormal glucose tolerance. RESEARCH DESIGN AND METHODS: Nine subjects (53 +/- 2 years; body mass index, 37 +/- 3 kg/m 2 [mean +/- SEM]) received a low-energy diet (3883 +/- 222 kJ/d) for 1 week, and then followed a modest lifestyle intervention program for up to 1 year. Body composition was estimated by hydrostatic weighing, and insulin secretion and action were assessed during a hyperglycemic clamp with superimposed arginine infusion and fat meal. Baseline and final tests were performed during weight stability. RESULTS: Significant improvements ( P < .05) were observed for body weight (-6.1 +/- 1.1 kg), body composition (-5.5 +/- 1.3 kg fat mass), fasting plasma glucose (-1.1 +/- 0.3 mmol/L), fasting insulin (-52 +/- 21 pmol/L), oral glucose tolerance, and insulin action (+24%), defined as an increase in glucose disposal rate relative to plasma insulin concentration during the hyperglycemic clamp. These improvements were independent of an acute effect of energy restriction or weight loss, because body weight was stable. CONCLUSIONS: These results suggest that the improvements in glucose tolerance with a modest lifestyle intervention were attributable to an improvement in insulin action, and provide evidence that despite persistent obesity (body mass index, 34.7 +/- 2.4 kg/m 2 ), long-term benefits can be achieved with relatively small weight loss in obese African Americans.

Black People↗
PubMed2005

Aerobic power and insulin action improve in response to endurance exercise training in healthy 77-87 yr olds.

Previous studies have demonstrated that frail octogenarians have an attenuated capacity for cardiovascular adaptations to endurance exercise training. In the present study, we determined the magnitude of cardiovascular and metabolic adaptations to high-intensity endurance exercise training in healthy, nonfrail elderly subjects. Ten subjects [8 men, 2 women, 80.3 yr (SD2.5)] completed 10-12 mo (108 exercise sessions) of a supervised endurance exercise training program consisting of 2.5 sessions/wk (SD 0.2), 58 min/session (SD 6), at an intensity of 83% (SD 5) of peak heart rate. Primary outcomes were maximal attainable aerobic power [peak aerobic capacity (Vo(2peak))]; serum lipids, oral glucose tolerance, and insulin action during a hyperglycemic clamp; body composition by dual-energy X-ray absorptiometry, and energy expenditure using doubly labeled water and indirect calorimetry. The training program resulted in an increase in Vo(2peak) of 15% (SD 7) [22.9 (SD 3.3) to 26.2 ml.kg(-1).min(-1) (SD 4.0); P < 0.0001]. Favorable lipid changes included reductions in total cholesterol (-8%; P = 0.002) and LDL cholesterol (-10%; P = 0.003), with no significant change in HDL cholesterol or triglycerides. Insulin action improved, as evidenced by a 29% increase in glucose disposal rate relative to insulin concentration during the hyperglycemic clamp. Fat mass decreased by 1.8 kg (SD 1.4) (P = 0.003); lean mass did not change. Total energy expenditure increased by 400 kcal/day because of an increase in physical activity. No change occurred in resting metabolism. In summary, healthy nonfrail octogenarians can adapt to high-intensity endurance exercise training with improvements in aerobic power, insulin action, and serum lipid and lipoprotein risk factors for coronary heart disease; however, the adaptations in aerobic power and insulin action are attenuated compared with middle-aged individuals.

Adaptation, Physiological↗
PubMed2004

Effect of obesity and insulin resistance on myocardial substrate metabolism and efficiency in young women.

BACKGROUND: Obesity is a risk factor for impaired cardiac performance, particularly in women. Animal studies suggest that alterations in myocardial fatty acid metabolism and efficiency in obesity can cause decreased cardiac performance. In the present study, we tested the hypothesis that myocardial fatty acid metabolism and efficiency are abnormal in obese women. METHODS AND RESULTS: We studied 31 young women (body mass index [BMI] 19 to 52 kg/m2); 19 were obese (BMI >30 kg/m2). Myocardial oxygen consumption (MVO2) and fatty acid uptake (MFAUp), utilization (MFAU), and oxidation (MFAO) were quantified by positron emission tomography. Cardiac work was measured by echocardiography, and efficiency was calculated as work/MVO2. BMI correlated with MVO2 (r=0.58, P=0.0006), MFAUp (r=0.42, P<0.05), and efficiency (r=-0.40, P<0.05). Insulin resistance, quantified by the glucose area under the curve (AUC) during an oral glucose tolerance test, correlated with MFAUp (r=0.55, P<0.005), MFAU (r=0.62, P<0.001), and MFAO (r=0.58, P<0.005). A multivariate, stepwise regression analysis showed that BMI was the only independent predictor of MVO2 and efficiency (P=0.0005 and P<0.05, respectively). Glucose AUC was the only independent predictor of MFAUp, MFAU, and MFAO (P<0.05, <0.005, and <0.005, respectively). CONCLUSIONS: In young women, obesity is a significant predictor of increased MVO2 and decreased efficiency, and insulin resistance is a robust predictor of MFAUp, MFAU, and MFAO. This increase in fatty acid metabolism and decrease in efficiency is concordant with observations made in experimental models of obesity. These metabolic changes may play a role in the pathogenesis of decreased cardiac performance in obese women.

Adult↗
PubMed2003

Fat-free foods supplemented with soy stanol-lecithin powder reduce cholesterol absorption and LDL cholesterol.

OBJECTIVE: The objective of this work was to show that fat-free, lecithin-formulated soy stanols lower cholesterol absorption and serum LDL cholesterol. DESIGN: Reduction in cholesterol absorption was measured in paired single-meal tests with or without formulated soy stanols (acute test), and changes in serum lipids were investigated in a 10-week, randomized, double-blind parallel trial in which formulated stanols or lecithin vehicle were given three times daily for the last 4 weeks (chronic test). SUBJECTS/SETTING: Forty-five normal or mildly hypercholesterolemic subjects were recruited for both studies. The 21 subjects (16 female, 5 male; mean age 32.5 years) in the absorption studies had the following mean lipid values: LDL cholesterol, 2.79 mmol/L and total cholesterol, 4.73 mmol/L. For the lipid reduction, 24 subjects (16 female, 8 male; mean age 50.6 years) were enrolled with mean LDL cholesterol and total cholesterol of 3.72 mmol/L and 5.66 mmol/L, respectively. INTERVENTION: Reduction in cholesterol absorption was measured using a lemonade beverage or egg whites that contained 625 mg stanols. Throughout the chronic study, subjects followed the American Heart Association Step I diet. During the 4-week treatment phase, subjects consumed daily a lemonade-flavored beverage containing either placebo or formulated soy stanols (1.9 g). MAIN OUTCOME MEASURES: Inhibition of cholesterol absorption was determined from the difference in plasma deuterated cholesterol enrichment after a test meal containing stanol-lecithin and one with lecithin vehicle only. In the chronic study, the primary endpoints were changes in LDL and total cholesterol. STATISTICAL ANALYSES PERFORMED: Paired or unpaired t tests were used to determine statistical significance. RESULTS: Stanol-lecithin reduced cholesterol absorption by 32.1% (P=.0045, n=10) and by 38.2% (P=.0022, n=11) when delivered in a lemonade-flavored beverage and in egg whites, respectively. Reduction in cholesterol absorption was strongly related to the initial level of absorbed cholesterol tracer in serum (r(s)=-0.739). Stanol-lecithin given in a beverage reduced total serum cholesterol by 10.1% (P=.0019, n=24) and LDL cholesterol by 14.3% (P=.0016, n=24). APPLICATIONS/CONCLUSIONS: Powdered soy stanol-lecithin lowers cholesterol absorption and LDL cholesterol when consumed in fat-free foods.

Adult↗
PubMed2003

Inhibition of cholesterol absorption by phytosterol-replete wheat germ compared with phytosterol-depleted wheat germ.

BACKGROUND: Low-fat vegetable foods contain phytosterols, but it is not known whether they are in biologically active forms or whether their concentrations are high enough to reduce cholesterol absorption and favorably affect lipid metabolism. OBJECTIVE: The objective was to establish whether the selective removal of phytosterols from wheat germ would increase the cholesterol absorption measured from test meals composed of wheat germ muffins. DESIGN: Wheat germ, which has a high content of phytosterols relative to total fat, was chosen as a low-fat test food. Cholesterol absorption was measured 3 times in 10 subjects. Each test meal was a muffin containing 30 mg heptadeuterated cholesterol tracer and, in random order, 80 g original wheat germ containing 328 mg phytosterols, wheat germ from which phytosterols had been selectively extracted, or extracted wheat germ reconstituted with purified phytosterols. Changes in cholesterol absorption were monitored by the measurement of tracer enrichment of plasma cholesterol 4 and 5 d after each meal with the use of negative ion mass spectrometry. RESULTS: Tracer enrichment of plasma cholesterol was 42.8% higher after consumption of phytosterol-free wheat germ than after that of the original wheat germ (0.415 +/- 0.035 compared with 0.291 +/- 0.024 micro mol tracer/mmol cholesterol; P < 0.01). Tracer enrichment of plasma cholesterol was not significantly different between the wheat germ with extracted-and-reconstituted phytosterol (0.305 +/- 0.022 micro mol tracer/mmol cholesterol) and the original wheat germ. CONCLUSION: The efficiency of cholesterol absorption from test meals was substantially lower after consumption of original wheat germ than after consumption of phytosterol-free wheat germ, which suggests that endogenous phytosterols in wheat germ and possibly in other low-fat vegetable foods may have important effects on cholesterol absorption and metabolism that are independent of major nutrients.

Absorption↗
PubMed2003

Creatine supplementation and athletic performance.

Nutritional supplements and other ergogenic aids have gained widespread use among professional, amateur, recreational, and student athletes for their potential to enhance athletic performance and provide a competitive edge. Creatine monohydrate is one of the more commonly used and potentially beneficial supplements that currently is viewed to be safe. Supplementation with oral creatine augments skeletal muscle creatine concentrations in most individuals, which has been shown to promote gains in lean body mass when used in conjunction with resistance training, to enhance power and strength, and to improve performance in intense exercise, especially during repeated bouts. Young athletes, however, must be cautious about taking creatine because its effects on growth and development are unknown and long-term safety has not been established. Variability in research study designs and small sample sizes have left many questions unanswered regarding the safety and efficacy of chronic supplementation. This is an active area of clinical investigation and the results of ongoing and future research should guide the appropriate use of creatine to enhance athletic performance among athletes of all ages.

Creatine↗
PubMed2002

Thiazolidinediones enhance insulin-mediated suppression of fatty acid flux in type 2 diabetes mellitus.

Type 2 diabetes mellitus is characterized by insulin-resistant glucose and lipid metabolism. Thiazolidinediones (TZDs) enhance insulin-mediated glucose disposal, but their effects on lipid kinetics are unknown. We evaluated the effect of the TZD troglitazone on insulin-mediated suppression of fatty acid and glycerol kinetics. Eight obese men and women (body mass index [BMI], 34.1 +/- 2.3 kg/m(2)) with insulin-requiring type 2 diabetes were studied before and after 12 weeks of troglitazone therapy (400 mg/d). Whole-body and abdominal fat masses were determined by dual-energy x-ray absorptiometry and magnetic resonance imaging, respectively. Palmitate and glycerol rates of appearance (R(a)) into plasma were evaluated during a 3-stage hyperinsulinemic euglycemic clamp, which spanned the physiologic range of plasma insulin concentrations that regulate lipolysis. Troglitazone therapy did not alter body composition. Palmitate and glycerol R(a) decreased progressively during each stage of hyperinsulinemia (P <.001). Suppression of palmitate R(a) by insulin was greater after than before troglitazone therapy (P <.001), whereas glycerol R(a) was unchanged. These results demonstrate that TZDs increase insulin-mediated suppression of fatty acid release into plasma in obese subjects with type 2 diabetes mellitus, which may contribute to their metabolic benefits. However, TZD therapy did not affect whole-body glycerol R(a), possibly because of upregulation of lipoprotein lipase action on plasma triglycerides.

Adipose Tissue↗
PubMed2002

Phytosterols that are naturally present in commercial corn oil significantly reduce cholesterol absorption in humans.

BACKGROUND: Although supplementing the diet with large quantities of phytosterols reduces cholesterol absorption and LDL-cholesterol concentrations, very little is known about the smaller amounts of phytosterols present naturally in food. Vegetable oils are the richest dietary source of phytosterols; corn oil contains 0.77% phytosterols by weight. OBJECTIVE: We tested the hypothesis that removing phytosterols from corn oil would increase cholesterol absorption when measured in single-meal tests containing corn oil as a source of fat. DESIGN: Free and esterified phytosterols were removed from corn oil on a kilogram scale by a new technique of competitive saturation adsorption to silica. Healthy subjects with a mean (+/-SEM) serum cholesterol concentration of 5.10 +/- 0.18 mmol/L received an otherwise sterol-free test breakfast on 2 occasions 2 wk apart that contained 35 mg hexadeuterated cholesterol and 30-35 g of a corn oil preparation. The plasma enrichment of tracer was measured by negative ion mass spectrometry. RESULTS: Cholesterol absorption was 38.0 +/- 10.2% higher after consumption of the sterol-free corn oil than after consumption of commercial corn oil with an identical fatty acid content (P = 0.005; n = 10). When corn oil phytosterols were added back to sterol-free corn oil at a concentration of 150 mg/test meal, cholesterol absorption was reduced by 12.1 +/- 3.7% (P = 0.03; n = 5) and by 27.9 +/- 9.1% (P = 0.01; n = 10) after inclusion of 300 mg phytosterols. CONCLUSIONS: Phytosterols comprising < 1% of commercial corn oil substantially reduced cholesterol absorption and may account for part of the cholesterol-lowering activity of corn oil previously attributed solely to unsaturated fatty acids.

Absorption↗
PubMed2002

Effects of trace components of dietary fat on cholesterol metabolism: phytosterols, oxysterols, and squalene.

The effect of dietary fats on serum cholesterol is widely assumed to be due solely to the fatty acids and cholesterol they contain. Phytosterols, sterol oxidation products, and sterol precursors such as squalene, however, are often present in dietary fats. Little is known of the physiology of these substances in natural foods and most published diet studies do not consider them at all. Supplementation of the diet with high-dose phytosterols is now recommended for prevention of heart disease, but both recent and old data strongly suggest that the lower levels of phytosterols naturally present in vegetable fats may also reduce cholesterol absorption and serum cholesterol substantially. Moreover, unmeasured phytosterols may confound otherwise well-controlled diet studies because there is an inverse correlation between phytosterol and saturated fatty acid content of vegetable fats. Sterol oxidation products, many of which are found in foods, are potent regulators of lipoprotein and cholesterol transport pathways in vitro. Squalene is a phytosterol precursor abundant in olive oil that is at least partly absorbed and then quantitatively converted to cholesterol. The effects of dietary triglyceride-derived fatty acids have not been experimentally separated from the effects of trace fat components in most clinical studies. A better understanding of the activity of sterol-related dietary components is needed to reduce variability in diet studies, accurately assess the effects of dietary fatty acids and to maximize the effectiveness of dietary treatment for hypercholesterolemia.

Cholesterol↗
PubMedDate not supplied

Bone mineral density response to caloric restriction-induced weight loss or exercise-induced weight loss: a randomized controlled trial.

BACKGROUND: Bone loss often accompanies weight loss induced by caloric restriction (CR), but whether bone loss accompanies similar weight loss induced by exercise (EX) is unknown. We tested the hypothesis that EX-induced weight loss is associated with less bone loss compared with CR-induced weight loss. METHODS: Forty-eight adults (30 women; 18 men; mean +/- SD age, 57 +/- 3 years; and mean +/- SD body mass index, 27 +/- 2 kg/m2) were randomized to 1 of 3 groups for 1 year: CR group (n = 19), regular EX group (n = 19), or a healthy lifestyle (HL) control group (n = 10). Primary outcome measure was change in hip and spine bone mineral density (BMD). Secondary outcomes were bone markers and hormones. RESULTS: Body weight decreased similarly in the CR and EX groups (10.7% +/- 6.3% [-8.2 +/- 4.8 kg] vs 8.4% +/- 6.3% [-6.7 +/- 5.6 kg]; P = .21), whereas weight did not change in the HL group (-1.2% +/- 2.5% [-0.9 +/- 2.0 kg]). Compared with the HL group, the CR group had decreases in BMD at the total hip (-2.2% +/- 3.1% vs 1.2% +/- 2.1%; P = .02) and intertrochanter (-2.1% +/- 3.4% vs 1.7 +/- 2.8%; P = .03). The CR group had a decrease in spine BMD (-2.2% +/- 3.3%; P = .009). Despite weight loss, the EX group did not demonstrate a decrease in BMD at any site. Body weight changes correlated with BMD changes in the CR (R = 0.61; P = .007) but not in the EX group. Bone turnover increased in both CR and EX groups. CONCLUSIONS: CR-induced weight loss, but not EX-induced weight loss, is associated with reductions in BMD at clinically important sites of fracture. These data suggest that EX should be an important component of a weight loss program to offset adverse effects of CR on bone.

Alkaline Phosphatase↗
PubMedDate not supplied

Effects of soy protein isolate and moderate exercise on bone turnover and bone mineral density in postmenopausal women.

OBJECTIVE: The aim of this study was to assess the independent and additive effects of soy protein isolate (SPI) and moderate-intensity exercise (EX) on bone turnover and bone mineral density (BMD). DESIGN: This study used a placebo-controlled, double-blind (soy), randomized 2 (SPI vs milk protein isolate [MPI]) x 2 (EX vs no EX) design. Sixty-one postmenopausal women were randomized, and 43 (62 +/- 5 y) completed the 9-month intervention (SPI, n = 10; MPI, n = 12; SPI + EX, n = 11; MPI + EX, n = 10). Serum C-terminal cross-linked telopeptides of type I collagen and serum bone-specific alkaline phosphatase were measured as markers of bone resorption and formation, respectively. BMD was measured by dual-energy x-ray absorptiometry. RESULTS: At 9 months, SPI reduced serum C-terminal cross-linked telopeptides (-13.3% +/- 15.3% vs -1.5% +/- 21.0%; P = 0.02) and serum bone-specific alkaline phosphatase (-4.7% +/- 14.7% vs 6.5% +/- 17.7%; P = 0.02) compared to milk protein isolate. EX attenuated the reduction in serum C-terminal cross-linked telopeptides (-1.9% +/- 21.6% vs -12.4% +/- 15.3%; P = 0.04); however, no EX effects were apparent in serum bone-specific alkaline phosphatase at 9 months (2.8% +/- 16.1% vs -1.0% +/- 18.3%; P = 0.28). Neither SPI nor EX affected BMD at any site; however, change in BMD was related to change in fat mass (r = 0.40, P < 0.05). CONCLUSIONS: In postmenopausal women (1) SPI reduces bone turnover with no impact on BMD over 9 months; (2) moderate-intensity endurance exercise training did not favorably alter bone turnover and had no impact on BMD; and (3) there were no additive effects of soy and exercise on bone turnover or BMD.

Absorptiometry, Photon↗
PubMedDate not supplied

Weight changes, exercise, and dietary patterns during freshman and sophomore years of college.

Weight gain and behavioral patterns during college may contribute to overweight and obesity in adulthood. The aims of this study were to assess weight, exercise, and dietary patterns of 764 college students (53% women, 47% men) during freshman and sophomore years. Students had their weight and height measured and completed questionnaires about their recent exercise and dietary patterns. At the beginning of freshman year, 29% of students reported not exercising, 70% ate fewer than 5 fruits and vegetables daily, and more than 50% ate fried or high-fat fast foods at least 3 times during the previous week. By the end of their sophomore year, 70% of the 290 students who were reassessed had gained weight (4.1+/-3.6 kg, p < .001), but there was no apparent association with exercise or dietary patterns. Future research is needed to assess the contributions of fat, muscle, and bone mass to observed weight gain and to determine the health implications of these findings.

Adult↗