Amy M. Goss

Effects of diet macronutrient composition on body composition and fat distribution during weight maintenance and weight loss

Qualitative aspects of diet may affect body composition and propensity for weight gain or loss. We tested the hypothesis that consumption of a relatively low glycemic load (GL) diet would reduce total and visceral adipose tissue under both eucaloric and hypocaloric conditions.

Favourable metabolic effects of a eucaloric lower‐carbohydrate diet in women with PCOS

Diet‐induced reduction in circulating insulin may be an attractive nonpharmacological treatment for women with polycystic ovary syndrome (PCOS) among whom elevated insulin may exacerbate symptoms by stimulating testosterone synthesis. This study was designed to determine whether a modest reduction in dietary carbohydrate (CHO) content affects β‐cell responsiveness, serum testosterone concentration and insulin sensitivity in women with PCOS.

Effects of a eucaloric reduced-carbohydrate diet on body composition and fat distribution in women with PCOS☆

OBJECTIVE To determine if consumption of a reduced-carbohydrate (CHO) diet would result in preferential loss of adipose tissue under eucaloric conditions, and whether changes in adiposity were associated with changes in postprandial insulin concentration. METHODS In a crossover-diet intervention, 30 women with PCOS consumed a reduced-CHO diet (41:19:40% energy from CHO:protein:fat) for 8 weeks and a standard diet (55:18:27) for 8 weeks. Body composition by DXA and fat distribution by CT were assessed at baseline and following each diet phase. Insulin AUC was obtained from a solid meal test (SMT) during each diet phase. RESULTS Participants lost 3.7% and 2.2% total fat following the reduced-CHO diet and STD diet, resp. (p<0.05 for difference between diets). The reduced-CHO diet induced a decrease in subcutaneous-abdominal, intra-abdominal, and thigh-intermuscular adipose tissue (-7.1%, -4.6%, and -11.5%, resp.), and the STD diet induced a decrease in total lean mass. Loss of fat mass following the reduced CHO diet arm was associated with lower insulin AUC (p<0.05) during the SMT. CONCLUSIONS In women with PCOS, consumption of a diet lower in CHO resulted in preferential loss of fat mass from metabolically harmful adipose depots, whereas a diet high in CHO appeared to promote repartitioning of lean mass to fat mass.

Insulin sensitivity is associated with thigh adipose tissue distribution in healthy postmenopausal women.

OBJECTIVE Evidence suggests intermuscular adipose tissue (IMAT) may be linked to insulin resistance, whereas thigh subcutaneous adipose tissue (SAT) may be related favorably with indices of metabolic health. However, whether adipose tissue depots of the thigh are differentially related to insulin sensitivity independent of total adiposity and other adipose tissue depots has not been determined. The objective of this study was to identify independent associations of the subcompartments of adipose tissue of the thigh with insulin sensitivity among 97 healthy early postmenopausal women. MATERIALS AND METHODS Computed tomography (CT) scans of the mid-thigh were used to assess Thigh-SAT, Thigh perimuscular adipose tissue (PMAT), and Thigh-IMAT. CT scans at the L4-L5 intervertebral space were used to assess intra-abdominal adipose tissue (IAAT) and Abdominal-SAT. Total body fat was measured by dual-energy X-ray absorptiometry (DXA). The insulin sensitivity index (S(I)) was assessed by using a frequently sampled intravenous glucose tolerance test with minimal model analysis. RESULTS Results indicated S(I) was positively associated with Thigh-SAT independent of total fat mass and other adipose tissue compartments. Among all women combined, S(I) was inversely associated with Thigh-IMAT independent of total fat mass. However, the relationship between S(I) and Thigh-IMAT was independent of IAAT only among women with high levels of Thigh-IMAT and IAAT. CONCLUSIONS This is the first study to demonstrate independent, opposing relationships of Thigh-SAT and Thigh-IMAT with insulin sensitivity in healthy postmenopausal women. Further research is needed to determine if these associations are causal in nature.

Longitudinal associations of the endocrine environment on fat partitioning in postmenopausal women

Among postmenopausal women, declining estrogen may facilitate fat partitioning from the periphery to the intra‐abdominal space. Furthermore, it has been suggested that excess androgens contribute to a central fat distribution pattern in women. The objective of this longitudinal study was to identify independent associations of the hormone milieu with fat distribution in postmenopausal women. Fifty‐three healthy postmenopausal women, either using or not using hormone replacement therapy (HRT) were evaluated at baseline and 2 years. The main outcomes were intra‐abdominal adipose tissue (IAAT), subcutaneous abdominal adipose tissue, and total thigh fat analyzed by computed tomography scanning and leg fat and total body fat mass measured by dual‐energy X‐ray absorptiometry. Serum estradiol, estrone, estrone sulfate, total testosterone, free testosterone, androstenedione, dehydroepiandrosterone sulfate), sex hormone‐binding globulin (SHBG), and cortisol were assessed. On average, in all women combined, IAAT increased by 10% (10.5 cm2) over 2 years (P < 0.05). Among HRT users, estradiol was inversely associated with, and estrone was positively associated with, 2‐year gain in IAAT. Among HRT nonusers, free testosterone was inversely associated with, and SHBG was positively associated with, 2‐year gain in IAAT. These results suggest that in postmenopausal women using HRT, greater circulating estradiol may play an integral role in limiting lipid deposition to the intra‐abdominal cavity, a depot associated with metabolically detrimental attributes. However, a high proportion of weak estrogens may promote fat partitioning to the intra‐abdominal cavity over time. Furthermore, among postmenopausal women not using HRT, greater circulating free testosterone may limit IAAT accrual.

Calorie restriction in overweight older adults: Do benefits exceed potential risks?

The evidence regarding recommendations of calorie restriction as part of a comprehensive lifestyle intervention to promote weight loss in obese older adults has remained equivocal for more than a decade. The older adult population is the fastest growing segment of the US population and a greater proportion of them are entering old age obese. These older adults require treatments based on solid evidence. Therefore the purpose of this review is three-fold: 1) to provide a more current status of the knowledge regarding recommendations of calorie restriction as part of a comprehensive lifestyle intervention to promote weight loss in obese older adults, 2) to determine what benefits and/or risks calorie restriction adds to exercise interventions in obese older adults, and 3) to consider not only outcomes related to changes in body composition, bone health, cardiometabolic disease risk, markers of inflammation, and physical function, but, also patient-centered outcomes that evaluate changes in cognitive status, quality of life, out-of-pocket costs, and mortality. Seven randomized controlled trials were identified that examined calorie restriction while controlling for exercise intervention effects. Overall, the studies found that calorie restriction combined with exercise is effective for weight loss. Evidence was mixed regarding other outcomes. The risk-benefit ratio regarding calorie restriction in older adults remains uncertain. Greater long-term follow-up is necessary, and complementary effectiveness studies are needed to identify strategies currently used by obese older adults in community settings.

Effects of Calorie Restriction in Obese Older Adults: The CROSSROADS Randomized Controlled Trial.

Background We lack a comprehensive assessment of the risks and benefits of calorie restriction in older adults at high risk for cardiometabolic disease. Calorie restriction may reduce visceral adipose tissue (VAT) but also have negative effects on lean mass and quality of life. Methods We conducted a 52-week, randomized controlled trial involving 164 older adults with obesity taking at least one medication for hyperlipidemia, hypertension, or diabetes. Interventions included an exercise intervention alone (Exercise), or with diet modification and body weight maintenance (Maintenance), or with diet modification and energy restriction (Weight Loss). The primary outcome was change in VAT at 12 months. Secondary outcomes included cardiometabolic risk factors, functional status, and quality of life. Results A total of 148 participants had measured weight at 12 months. Despite loss of -1.6% ± 0.3% body fat and 4.1% ± 0.7% initial body weight, Weight Loss did not have statistically greater loss of VAT (-192.6 ± 185.2 cm3) or lean mass (-0.4 ± 0.3 kg) compared with Exercise (VAT = -21.9 ± 173.7 cm3; lean mass = 0.3 ± 0.3 kg). Quality of life improved in all groups with no differences between groups. No significant changes in physical function were observed. Weight Loss had significantly greater improvements in blood glucose (-8.3 ± 3.6 mg/dL, p < .05) and HDL-cholesterol (5.3 ± 1.9, p < .01) compared with Exercise. There were no group differences in the frequency of adverse events. Conclusions While moderate calorie restriction did not significantly decrease VAT in older adults at high risk for cardiometabolic disease, it did reduce total body fat and cardiometabolic risk factors without significantly more adverse events and lean mass loss.

Peri-muscular adipose tissue may play a unique role in determining insulin sensitivity/resistance in women with polycystic ovary syndrome

STUDY QUESTION Do the determinants of insulin sensitivity/resistance differ in women with and without polycystic ovary syndrome (PCOS)? SUMMARY ANSWER Peri-muscular thigh adipose tissue is uniquely associated with insulin sensitivity/resistance in women with PCOS, whereas adiponectin and thigh subcutaneous adipose are the main correlates of insulin sensitivity/resistance in women without PCOS. WHAT IS KNOWN ALREADY In subject populations without PCOS, insulin sensitivity/resistance is determined by body fat distribution and circulating concentrations of hormones and pro-inflammatory mediators. Specifically, visceral (intra-abdominal) adipose tissue mass is adversely associated with insulin sensitivity, whereas thigh subcutaneous adipose appears protective against metabolic disease. Adiponectin is an insulin-sensitizing hormone produced by healthy subcutaneous adipose that may mediate the protective effect of thigh subcutaneous adipose. Testosterone, which is elevated in PCOS, may have an adverse effect on insulin sensitivity/resistance. STUDY DESIGN, SIZE, DURATION Cross-sectional study of 30 women with PCOS and 38 women without PCOS; data were collected between 2007 and 2011. PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were group-matched for obesity, as reflected in BMI (Mean ± SD; PCOS: 31.8 ± 6.0 kg/m2; without PCOS: 31.5 ± 5.0 kg/m2). The whole-body insulin sensitivity index (WBISI) was assessed using a mixed-meal tolerance test; Homeostasis Model Assessment-Insulin resistance (HOMA-IR) was determined from fasting insulin and glucose values. Adipose tissue distribution was determined by computed tomography (CT) scan. Partial correlation analysis, adjusting for total fat mass, was used to identify correlates of WBISI and HOMA-IR within each group of women from measures of body composition, body fat distribution, reproductive-endocrine hormones and adipokines/cytokines. Stepwise multiple linear regression analysis was used to identify the variables that best predicted WBISI and HOMA-IR. MAIN RESULTS AND THE ROLE OF CHANCE Among women with PCOS, both WBISI and HOMA-IR were best predicted by peri-muscular adipose tissue cross-sectional area. Among women without PCOS, both WBISI and HOMA-IR were best predicted by adiponectin and thigh subcutaneous adipose tissue. LIMITATIONS, REASONS FOR CAUTION Small sample size, group matching for BMI and age, and the use of surrogate measures of insulin sensitivity/resistance. WIDER IMPLICATIONS OF THE FINDINGS Because insulin resistance is the root cause of obesity and comorbidities in PCOS, determining its cause could lead to potential therapies. Present results suggest that peri-muscular adipose tissue may play a unique role in determining insulin sensitivity/resistance in women with PCOS. Interventions such as restriction of dietary carbohydrates that have been shown to selectively reduce fatty infiltration of skeletal muscle may decrease the risk for type 2 diabetes in women with PCOS. STUDY FUNDING/COMPETING INTEREST(S) The study was supported by National Institutes of Health grants R01HD054960, R01DK67538, P30DK56336, P60DK079626, M014RR00032 and UL1RR025777. The authors have no conflicts of interest. TRIAL REGISTRATION NUMBER NCT00726908.

Calorie Restriction in Overweight Seniors: Response of Older Adults to a Dieting Study: The CROSSROADS Randomized Controlled Clinical Trial

We conducted a study designed to evaluate whether the benefits of intentional weight loss exceed the potential risks in a group of community-dwelling obese older adults who were at increased risk for cardiometabolic disease. The CROSSROADS trial used a prospective randomized controlled design to compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition and adipose tissue deposition (Specific Aim #1: To compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition, namely visceral adipose tissue), cardiometabolic disease risk (Specific Aim #2: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on cardiometabolic disease risk), and functional status and quality of life (Specific Aim #3: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on functional status and quality of life). Participants were randomly assigned to one of three groups: Exercise Only (Control) Intervention, Exercise + Diet Quality + Weight Maintenance Intervention, or Exercise + Diet Quality + Weight Loss Intervention. CROSSROADS utilized a lifestyle intervention approach consisting of exercise, dietary, and behavioral components. The development and implementation of the CROSSROADS protocol, including a description of the methodology, detailing specific elements of the lifestyle intervention, assurances of treatment fidelity, and participant retention; outcome measures and adverse event monitoring; as well as unique data management features of the trial results, are presented in this article.

Oral Supplementation with Beta-Hydroxy-Beta-Methylbutyrate, Arginine, and Glutamine Improves Lean Body Mass in Healthy Older Adults

ABSTRACT Oral intake of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine may ameliorate muscle loss by stimulating protein synthesis and decreasing protein degradation while simultaneously decreasing inflammation. Previous studies provide evidence for improvement in body composition with dietary supplementation of these ingredients among patients with muscle-wasting diseases. The objectives of this study were to examine the effects of this amino acid mixture on lean body mass, muscle volume, and physical function among healthy older adults. Thirty-one community-dwelling men and women, aged 65–89 years, were randomized to either two oral doses of the amino acid supplement (totaling 3 g HMB, 14 g arginine, 14 g glutamine) or placebo daily for six months. At baseline and month six, lean body mass was measured by air displacement plethysmography, dual-energy X-ray absorptiometry (DXA), and four-compartment model. Muscle volume of quadriceps was quantified by magnetic resonance imaging (MRI), and participants performed a battery of tests to assess physical function. As compared to the placebo group, the treatment group exhibited improvement in a timed stair climb (p =.016) as well as significant increases in lean body mass by all methods of assessment (p <.05). Regional analysis by DXA revealed increased arm lean mass in the supplement group only (p =.035). However, no change was observed in MRI-derived quadriceps volume. Dietary supplementation with HMB, arginine, and glutamine improved total body lean mass among a small sample of healthy older adults. Further research is indicated to elucidate mechanisms of action and to determine whether supplementation may benefit frail elders. Registered under ClinicalTrials.gov identifier no. NCT01057082.