Weight Loss Programs May Have Beneficial or Adverse Effects on Fat Mass and Insulin Sensitivity in Overweight and Obese Black Women

J. Racial and Ethnic Health Disparities (2014) 1:140–147 DOI 10.1007/s40615-014-0006-6 Weight Loss Programs May Have Beneficial or Adverse Effects on Fat Mass and Insulin Sensitivity in Overweight and Obese Black Women Benjamin Leon & Bernard V. Miller III & Gloria Zalos & Amber B. Courville & Anne E. Sumner & Tiffany M. Powell-Wiley & Mary F. Walter & Myron A. Waclawiw & Richard O. Cannon III Received: 16 October 2013 / Revised: 17 December 2013 / Accepted: 2 January 2014 / Published online: 5 March 2014 # The Author(s) 2014. This article is published with open access at Springerlink.com Abstract Objective Weight loss interventions have produced little change in insulin sensitivity in black women, but mean data may obscure metabolic benefit to some and adverse effects for others. Accordingly, we analyzed insulin sensitivity relative to fat mass change following a weight loss program. Design and Methods Fifty-four black women (BMI range 25.9 to 54.7 kg/m2) completed the 6-month program that included nutrition information and worksite exercise facilities. Fat mass was measured by dual-energy X-ray absorptiometry, and insulin sensitivity index (SI) was calculated from an insulin-modified intravenous glucose tolerance test using the minimal model. Results Baseline SI (range 0.74 to 7.58 l/mU−1•min−1) was inversely associated with fat mass (r= −0.516, p<0.001), independent of age. On average, subjects lost fat mass (baseline B. Leon : G. Zalos : T. M. Powell-Wiley : R. O. Cannon III (*) Cardiovascular and Pulmonary Branch, National Heart, Lung, and Blood Institute, Building 10-CRC Room 5-3330, 10 Center Drive, Bethesda, MD 20892, USA e-mail: M. A. Waclawiw Office of Biostatistics Research, National Heart, Lung, and Blood Institute, Bethesda, MD, USA B. V. Miller III : A. E. Sumner Diabetes, Endocrinology and Obesity Branch, Clinical Center; National Institutes of Health, Bethesda, MD, USA M. F. Walter Core for Clinical Laboratory Services, Clinical Center; National Institutes of Health, Bethesda, MD, USA A. B. Courville Nutrition Department, Clinical Center; National Institutes of Health, Bethesda, MD, USA 40.8±12.4 to 39.4±12.6 kg [mean±SD], P<0.01), but 17 women (32 %) actually gained fat mass. SI for the group was unchanged (baseline 3.3±1.7 to 3.2±1.6, P=0.67). However, the tertile with greatest fat mass loss (−3.6 kg, range −10.7 to −1.7 kg) improved insulin sensitivity (SI +0.3±1.2), whereas the tertile with net fat mass gain (+0.9 kg, range −0.1 to + 3.8 kg) had reduced insulin sensitivity (SI −0.7±1.3) from baseline values (P<0.05 by ANOVA). Conclusions Black women in a weight loss program who lose fat mass may have improved insulin sensitivity, but fat mass gain with diminished sensitivity is common. Additional support for participants who fail to achieve fat mass loss early in an intervention may be required for success. Keywords Obesity . insulin sensitivity . women . race . intervention Introduction The obesity epidemic has steadily worsened as nearly 70 % of adults in the USA are at least overweight and more than onethird are obese [1, 2]. The prevalence of obesity is the highest among underrepresented minority populations, particularly blacks who have the highest age-adjusted rate of obesity nationwide [1, 2]. Additionally, blacks also have a disproportionately high prevalence of type 2 diabetes and are at greater risk of developing associated cardiovascular complications including coronary artery disease, myocardial infarction, stroke, congestive heart failure, and peripheral vascular disease [3–6]. Major contributors to the growing obesity epidemic are inactivity and excess energy intake [7]. Evidence suggests that the work place contributes to the prevalence of obesity as employees in the USA are sedentary for large portions of J. Racial and Ethnic Health Disparities (2014) 1:140–147 the workday [7, 8]. To counter the mounting obesity rates, many organizations have initiated wellness programs at the work site to achieve weight loss by encouraging exercise and reduced caloric intake [9–14]. While many of these programs have been effective in promoting weight loss and improving health measures among whites, black women have been less successful in achieving these ends [15]. Therefore, we hypothesized that an intervention at the worksite that provides women with healthful information, either through interactive group sessions or internet-based tools, as well as exercise resources in the work place would enable fat mass loss and improve insulin-mediated glucose metabolism in overweight and obese black women. Specifically, we proposed that this decrease in fat mass would improve insulin sensitivity for those women who completed the diet and exercise program. Methods and Procedures Study population Overweight (body mass index [BMI] 25 to <30 kg/m2) and obese (BMI≥30 kg/m2) nondiabetic (fasting glucose <126 mg/dL) black (by self-report) female employees of the National Institutes of Health (NIH), Bethesda, Maryland were enrolled. Participants were recruited by flyers distributed across the Bethesda campus of NIH and selfidentified as healthy without participation in structured exercise or weight loss programs and weight stable (fluctuation in weight < 5 %) over the previous 3 months. Women were excluded from participation if screening blood work revealed anemia (hemoglobin <11 g/dL), liver, kidney, or thyroid disease. Prescription medications at stable doses for at least 2 months – including hormonal preparations for thyroid dysfunction or estrogen preparations (i.e., birth control or postmenopausal hormone therapy) – were permitted, but a change in medications during the study was prespecified as an exclusion criterion from further participation due to the potential of confounding main outcome measures. The protocol was approved by the Institutional Review Board of the National Heart Lung and Blood (NHLBI) and registered in www. ClinicalTrials.gov (NCT00666172) prior to study initiation. All subjects provided informed consent. Study Design All participants were provided internet-based nutrition and exercise information created by NHLBI for employees (recent version can be found at http://apps.nhlbi. nih.gov/keepthebeat) that included recommendations from the Department of Health and Human Services and the US Department of Agriculture [16]. The web site included walking paths around the NIH Bethesda campus, sample menus, healthful lifestyle information, and tools for counting calories. Each participant was given a pedometer (Walk4Life, Plainfield, IL) with instructions to increase average daily step count by 5,000 steps over their baseline average and given 141 card-key access to private fitness rooms located in three buildings on campus, each equipped with aerobic exercise equipment (e.g., treadmill, elliptical machine, and supine bicycle). Participants were also encouraged to continue physical activity – especially walking – on nonwork days. Enroll (...truncated)