Krista Casazza

Myths, Presumptions, and Facts about Obesity

BACKGROUND Many beliefs about obesity persist in the absence of supporting scientific evidence (presumptions); some persist despite contradicting evidence (myths). The promulgation of unsupported beliefs may yield poorly informed policy decisions, inaccurate clinical and public health recommendations, and an unproductive allocation of research resources and may divert attention away from useful, evidence-based information. METHODS Using Internet searches of popular media and scientific literature, we identified, reviewed, and classified obesity-related myths and presumptions. We also examined facts that are well supported by evidence, with an emphasis on those that have practical implications for public health, policy, or clinical recommendations. RESULTS We identified seven obesity-related myths concerning the effects of small sustained increases in energy intake or expenditure, establishment of realistic goals for weight loss, rapid weight loss, weight-loss readiness, physical-education classes, breast-feeding, and energy expended during sexual activity. We also identified six presumptions about the purported effects of regularly eating breakfast, early childhood experiences, eating fruits and vegetables, weight cycling, snacking, and the built (i.e., human-made) environment. Finally, we identified nine evidence-supported facts that are relevant for the formulation of sound public health, policy, or clinical recommendations. CONCLUSIONS False and scientifically unsupported beliefs about obesity are pervasive in both scientific literature and the popular press. (Funded by the National Institutes of Health.).

Effect of Dietary Adherence with or without Exercise on Weight Loss: A Mechanistic Approach to a Global Problem

CONTEXT Weight loss using low-calorie diets produces variable results, presumably due to a wide range of energy deficits and low-dietary adherence. OBJECTIVE Our objective was to quantify the relationship between dietary adherence, weight loss, and severity of caloric restriction. DESIGN AND SETTING Participants were randomized to diet only, diet-endurance training, or diet-resistance training until body mass index (BMI) was less than 25 kg/m(2). PARTICIPANTS Healthy overweight (BMI 27-30) premenopausal women (n = 141) were included in the study. INTERVENTIONS An 800-kcal/d(-1) diet was provided, and the exercise groups were engaged in three sessions per week. MAIN OUTCOMES Dietary adherence, calculated from total energy expenditure determined by doubly labeled water measurements and dual-energy x-ray absorptiometry body composition changes, and degree of caloric restriction were determined. RESULTS All groups had similar weight loss (approximately 12.1 +/- 2.5 kg) and length of time to reach target BMI (approximately 158 +/- 70 d). Caloric restriction averaged 59 +/- 9%, and adherence to diet was 73 +/- 34%. Adherence to diet was inversely associated to days to reach target BMI (r = -0.687; P < 0.01) and caloric restriction (r = -0.349; P < 0.01). Association between adherence to diet and percent weight lost as fat was positive for the diet-endurance training (r = 0.364; P < 0.05) but negatively correlated for the diet-only group (r = -0.387; P < 0.05). CONCLUSIONS Dietary adherence is strongly associated with rates of weight loss and adversely affected by the severity of caloric restriction. Weight loss programs should consider moderate caloric restriction relative to estimates of energy requirements, rather than generic low-calorie diets.

Differential Influence of Diet and Physical Activity on Components of Metabolic Syndrome in a Multiethnic Sample of Children

BACKGROUND Treatment of the metabolic syndrome in adults is generally approached with diet and physical activity. The influence of diet and physical activity on cardiometabolic outcomes in children has not been clearly established. OBJECTIVE The main objective of this study was to test the hypothesis that the distribution of energy from fat and carbohydrate in addition to limited time spent engaging in physical activity would contribute to the prevalence of the metabolic syndrome and its components in a multiethnic pediatric population. DESIGN Observational, cross-sectional study. Diet was assessed by two 24-hour recalls, physical activity by accelerometry, body composition by dual-energy absorptiometry, and glucose and lipid levels using fasting sera. MAIN OUTCOME MEASURES Presence of metabolic syndrome and its components. SUBJECTS 202 African-American (n=79), white (n=68), or Hispanic (n=55) healthy children aged 7 to 12 years. STATISTICAL ANALYSIS The contribution of diet and physical activity to the metabolic syndrome and its components were assessed by logistic regression and multiple linear regression analyses. RESULTS Prevalence of the metabolic syndrome in the total sample was 8.4%, with Hispanics more likely than whites and African Americans to meet the criteria. A greater intake of energy from carbohydrate was related to a greater waist circumference and higher concentrations of triglyceride and glucose particularly apparent within the African-American sample (P<0.05). Fat intake was associated with a lower waist circumference (P<0.05) and with lower concentrations of triglyceride (P<0.05) and glucose (P<0.001) in the total sample. Greater moderate/hard physical activity was associated with higher high-density lipoprotein cholesterol concentrations in whites (P<0.05). Increased sedentary behavior was related to greater glucose concentration in whites and Hispanics (P<0.05 for both). CONCLUSIONS Diet composition was more closely related to the components of the metabolic syndrome than was physical activity, with carbohydrate intake being adversely related to waist circumference, triglyceride levels, and glucose levels. Furthermore, relationships among diet and metabolic syndrome outcomes were stronger among African-American children, suggesting that nutrition interventions in this group may be particularly beneficial.

Parental feeding practices and socioeconomic status are associated with child adiposity in a multi-ethnic sample of children

Parental feeding practices have been associated with childrens weight status, but results have been inconsistent across populations. Research is needed to elucidate the relationship between parental feeding practices and adiposity in diverse populations. The present study tested if: (1) parental feeding practices differed by race/ethnicity, (2) parental pressure to eat and parental restriction were associated with adiposity levels, and (3) to investigate the relationship between parental feeding practices and/or child adiposity with socioeconomic status (SES). Structural equations modeling was conducted to test the model in 267 children aged 7-12 years self-identified as African American (AA), European American (EA), or Hispanic American (HA) from economically diverse backgrounds. Dual energy X-ray absorptiometry and computed tomography scanning were used to determine body composition and abdominal fat distribution, respectively. Parental restriction was a significant predictor of child adiposity while parental pressure to eat had an inverse relationship with child adiposity. HA parents reported significantly higher levels of restriction and pressure to eat, whereas EA parents reported the lowest. SES was positively associated with child adiposity and inversely related to parental restriction and pressure to eat. Thus, parental feeding practices differ across racial/ethnic groups and SES and may contribute to population differences in child adiposity.

Do neighbourhoods matter? Neighbourhood disorder and long-term trends in serum cortisol levels

Background Characteristics associated with low socioeconomic status neighbourhoods may put children at risk for unique chronic stressors that affect cortisol levels. This research sought to explore whether neighbourhood stressor exposure affected serum cortisol levels among children. Methods A total of 148 African and European-American children with an average age of 8.28 years participated in a longitudinal study evaluating ethnic differences in body composition and disease risk. Five waves of data were included in analyses. Mixed modelling was used to explore neighbourhood stressors, which was a composite index of five items for zip code level poverty and physical disorder, and serum cortisol outcomes for the full sample, by race/ethnicity and gender. Adjustments were made for individual level correlates age, pubertal status, gender and total fat mass. Results Neighborhood disorder was predictive of lower serum cortisol levels among African-American children (p<0.05), such that higher neighbourhood stressor exposure resulted in lower serum cortisol over time compared with individuals in socially ordered neighbourhoods. Neighbourhood disorder was marginally significant and predictive of higher serum cortisol among European-American children (p<0.10). Transition to a higher pubertal status, nested in age was also predictive of lower serum cortisol levels (p<0.01) among European-American children. Conclusion Children who are exposed to negative socioenvironmental climates over time are more likely to have altered serum cortisol levels. This may be an adaptive mechanism to cope with stress; however, disrupted cortisol levels may have negative effects on general physical and mental health.

Weighing the Evidence of Common Beliefs in Obesity Research

Obesity is a topic on which many views are strongly held in the absence of scientific evidence to support those views, and some views are strongly held despite evidence to contradict those views. We refer to the former as “presumptions” and the latter as “myths.” Here, we present nine myths and 10 presumptions surrounding the effects of rapid weight loss; setting realistic goals in weight loss therapy; stage of change or readiness to lose weight; physical education classes; breastfeeding; daily self-weighing; genetic contribution to obesity; the “Freshman 15”; food deserts; regularly eating (versus skipping) breakfast; eating close to bedtime; eating more fruits and vegetables; weight cycling (i.e., yo-yo dieting); snacking; built environment; reducing screen time in childhood obesity; portion size; participation in family mealtime; and drinking water as a means of weight loss. For each of these, we describe the belief and present evidence that the belief is widely held or stated, reasons to support the conjecture that the belief might be true, evidence to directly support or refute the belief, and findings from randomized controlled trials, if available. We conclude with a discussion of the implications of these determinations, conjecture on why so many myths and presumptions exist, and suggestions for limiting the spread of these and other unsubstantiated beliefs about the obesity domain.

Associations of Fibroblast Growth Factor-23 with Markers of Inflammation, Insulin Resistance and Obesity in Adults

Introduction Elevated fibroblast growth factor-23 (FGF23) is an established marker of cardiovascular disease. The underlying reason(s) for the rise accompanying cardiovascular health decline are unclear. Prior studies have shown that FGF23 concentrations are associated with markers of inflammation and insulin resistance but they have been limited by a focus on persons with chronic kidney disease (CKD) and lack of race and sex diversity. The objective of this study was to examine the associations of FGF23 and markers of inflammation, insulin resistance, and anthropometrics in a large cohort of community-dwelling adults. Methods Associations of FGF23 with markers of inflammation [interleukin-6 (IL-6), IL-10, high sensitivity-CRP (hsCRP)], insulin utilization [resistin, adiponectin, homeostatic model assessment of insulin resistance (HOMA-IR)] and anthropometrics [BMI and waist circumference (WC)] were examined cross-sectionally in a 1,040 participants randomly selected from the Reason for Geographic and Racial Differences in Stroke (REGARDS) Study, a national study of black and white adults ≥45 years. Effect modification by race and CKD status was tested, and stratified models were analyzed accordingly. Results Median FGF23 concentration was 69.6 RU/ml (IQR: 53.2, 102.7). Higher quartiles of FGF23 were associated with higher mean concentrations of IL-6, IL-10, hsCRP and resistin (P trend<0.001 for all). There were no significant differences in HOMA-IR, adiponectin concentrations, BMI, or WC across FGF23 quartiles in the crude analyses. CKD significantly modified the relationships between FGF23 and inflammatory markers, HOMA-IR, BMI and WC (P ≤ 0.01 for all). In linear regression models adjusted for sociodemographic and clinical variables, FGF23 was positively associated with IL-6, hsCRP, IL-10, HOMA-IR, BMI and WC in individuals without CKD, but not among individuals with CKD. Additionally, FGF23 was positively associated with resistin irrespective of CKD status. Conclusions Elevated FGF23 concentrations may be considered a biomarker for decline in metabolic function among individuals with normal kidney function.

Associations among Insulin, Estrogen, and Fat Mass Gain over the Pubertal Transition in African-American and European-American Girls

CONTEXT Age at menarche (AgeM) is earlier in African-American (AA) than in European-American (EA) girls. Neither the physiological cause nor the health implications of this difference are known. OBJECTIVE We tested the hypotheses that higher insulin among AA vs. EA precipitates an earlier elevation of estradiol (E2), an associated earlier AgeM, and greater gain in body fat. SETTING The study was conducted at a university research laboratory and General Clinical Research Center. PARTICIPANTS Subjects were 137 girls (57 AA and 80 EA) aged 7-15 yr. DESIGN The study had a longitudinal design. Annual evaluations were conducted for body composition by dual-energy X-ray absorptiometry, acute insulin response to glucose (AIRg) by iv glucose tolerance test, and reproductive-endocrine profile. MAIN OUTCOME MEASURES Multiple linear regression modeling and mixed model analyses were used to identify independent predictors of AgeM and E2 concentration at menarche. RESULTS AgeM was significantly earlier in AA vs. EA (10.8 vs. 11.6 yr). Neither E2 nor insulin was a significant independent predictor of AgeM. AIRg was a significant predictor of E2 concentration. AA had higher E2 than EA (P < 0.01), and girls with higher AIRg had higher E2. Total fat increased with age in both EA and AA. However, among EA, the increase in fat mass was similar both before and after menarche (9.4%/yr before vs. 10.0%/yr after), whereas among AA, fat deposition nearly doubled after menarche (8.4%/yr before vs. 14.9%/yr after). CONCLUSION Results did not support a direct cause-and-effect relationship between higher insulin, higher E2, and earlier AgeM in AA girls. However, the data suggested that higher insulin was associated with higher E2. Furthermore, reproductive maturation appeared to be associated with an acceleration of fat deposition among AA girls.

Neighborhood-Level Disadvantage Is Associated with Reduced Dietary Quality in Children

Research has linked neighborhood socioeconomic status to differential dietary quality among adults. However, the relationship between neighborhoods and childrens diet remains understudied. The aim of this research was to examine whether neighborhood disadvantage (eg, socioeconomic status, social and physical disorder) affected dietary quality among children. Data for this cross-sectional study were gathered between June 2005 and December 2008. Research participants included 182 children aged 7 to 12 years who were Hispanic (26%), white (28%), and African American (45%). Dietary intake was gathered via two 24-hour recalls and analyzed using the Nutrition Data System for Research. Descriptive statistics and analyses of variance were conducted to determine whether there were significant differences in dietary intakes by quartile grouping of neighborhood disadvantage. Multivariate linear regression analyses were used to determine whether neighborhood disadvantage (as a continuous measure) was associated with dietary quality. Overall, there were no significant differences in total caloric intake; however, children in disadvantaged neighborhoods consumed a greater percentage of calories from fat (P=0.039), trans fat (P=0.018), and had a higher sodium intake (P=0.01). The results suggest that neighborhood factors may contribute to dietary quality among children. Future interventions should assess mechanisms to improve the availability of healthful foods, while taking into account neighborhood-level conditions.

Impact of weight cycling on risk of morbidity and mortality.

Unintentional weight gain is commonly observed in adult humans, often provoking intentional weight loss attempts followed by unintentional weight regain. This episodic variation in body weight over a period of time has been referred to as ‘weight cycling’. Over the last two decades, weight cycling has been associated with a number of morbid health conditions and increased mortality. This article provides a comprehensive evaluation of recent weight‐cycling evidence, looks to understand design differences between studies and study outcomes, assesses the need for further research on particular health outcomes, and proposes alternative methodologies that will bridge the needs and capabilities of research. Searches were conducted per PRISMA guidelines. Articles on weight cycling in the literature were initially identified using search strings in PubMed. Eligibility assessment of the remaining articles was performed independently by three reviewers to identify publications that presented direct evidence. Twenty human studies (in addition to seven animal studies) were selected and retained; 12 accounted for the intentionality of weight loss. Although weight regain following successful weight loss remains one of the most challenging aspects of body‐weight regulation, evidence for an adverse effect of weight cycling appears sparse, if it exists at all.