Bisakha Sen

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.).

The Relationship Between Built Environments and Physical Activity: A Systematic Review

OBJECTIVES We conducted a systematic review of the literature examining the relationship between built environments (e.g., parks, trails, sidewalks) and physical activity (PA) or obesity rates. METHODS We performed a 2-step inclusion protocol to identify empirical articles examining any form of built environment and any form of PA (or obesity rate) as the outcome. We extracted data from included abstracts for analysis by using a standard code sheet developed for this study. RESULTS Of 169 included articles, 89.2% reported beneficial relationships-but virtually all articles utilized simple observational study designs not suited for determining causality. Studies utilizing objective PA measures (e.g., pedometer) were 18% less likely to identify a beneficial relationship. Articles focusing on children in community settings (-14.2%), those examining direct measures of obesity (-6.2%), or those with an academic first author (-3.4%) were less likely to find a beneficial relationship. CONCLUSIONS Policymakers at federal and local levels should encourage more rigorous scientific research to determine whether altered built environments will result in increased PA and decreased obesity rates.

Frequency of Family Dinner and Adolescent Body Weight Status: Evidence from the National Longitudinal Survey of Youth, 1997

Objective: To explore associations between overweight status and the frequency of family dinners (FFD) for adolescents and how those associations differ across race and ethnicity.

Does alcohol-use increase the risk of sexual intercourse among adolescents? Evidence from the NLSY97

This study investigates the causal link between alcohol-use and adolescent sexual activity. In a recent paper, using data from the 1995 wave of the National Longitudinal Study of Adolescent Health, Rees et al. [Journal of Health Economics 20 (5) (2001)] found little evidence of such a link. The data used here are from the National Longitudinal Study of Youth, 1997 (NLSY97), and results indicate that alcohol-use increases the probability of sexual intercourse, even after accounting for the potential endogeneity. However, consistent with Rees et al., there is less evidence that heavy drinking has a significant effect on sexual intercourse.

The relationship between frequency of family dinner and adolescent problem behaviors after adjusting for other family characteristics

OBJECTIVE To examine the association between frequency of family dinners (FFD) and selected problem behaviors for adolescents after adjusting for family connectedness, parental awareness, other family activities, and other potentially confounding factors. METHODS Data are drawn from the National Longitudinal Survey of Youth, 1997. The primary variable of interest is self-reported FFD in a typical week. Problem behaviors studied are substance-use, physical violence, property-destruction, stealing, running away from home, andgang membership. Multivariate logistic models are estimated for each behaviors. Linear regression models are estimated for behavior-frequency for the sub-samples engaging in them. Analysis is done separately by gender. RESULTS FFD is negatively associated with substance-use and running away for females; drinking, physical violence, property-destruction, stealing and running away for males. CONCLUSION Family meals are negatively associated to certain problem behaviors for adolescents even after controlling rigorously for potentially confounding factors. Thus, programs that promote family meals are beneficial.

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.

Teen Motherhood and Long-Term Health Consequences

The objective of this article is to examine the association of teen motherhood and long-term physical and mental health outcomes. The physical and mental health components (PCS and MCS) of the SF-12 Healthy Survey in the NLSY79 health module were used to assess long-term health outcomes of women who experienced teenage motherhood. Various familial, demographic, and environmental characteristics were indentified and controlled for that may have predicted teen motherhood and long-term health outcomes. The two comparison groups for teen mothers were women who experienced teen-pregnancy only and women who were engaged in unprotected sexual activity as a teenage but did not experience pregnancy. Multivariate ordinary least squares regression was used for analysis. The average PCS and MCS for teen mothers was 49.91 and 50.89, respectively. Teen mothers exhibited poorer physical health later in life compared to all women as well as the comparison groups. When controlling for age, teen mothers had significantly lower PCS and MCS scores compared to all other women. Furthermore, when controlling for familial, demographic, and environmental characteristics, teen mothers exhibited significantly lower PCS and MCS scores. When comparing teen mothers to the two comparison groups, PCS was not statistically different although MCS was significantly lower in the teen-pregnancy group. Teen motherhood does lead to poorer physical health outcomes later in life. On the other hand, poorer mental health outcomes in later life may be attributed to the unmeasured factors leading to a teen pregnancy and not teen motherhood itself. Additional research needs to be conducted on the long-term consequences of teen motherhood.

Can Beer Taxes Affect Teen Pregnancy? Evidence Based on Teen Abortion Rates and Birth Rates

Economists have investigated the effects of increased alcohol taxes on various alcohol-related phenomena like traffic fatalities, but to my knowledge, this study is the first to investigate the effects of beer taxes on teen pregnancy outcomes, namely abortion and birth rates. The study employs state-level data for 15–19-year-old women for the years 1985, 1988, 1992, and 1996. The smallness of the panel imposes some constraints on the statistical methods used. Results indicate that higher beer taxes have statistically significant negative effects on teen abortion rates, though the magnitudes of the effects are quite small. Effects on birthrates are statistically insignificant. This suggests that increased beer taxes may help prevent some unwanted pregnancies that would typically be terminated via abortions rather than culminating in live births. However, the small magnitudes of the effects strongly caution against relying on increased beer taxes to noticeably reduce teen pregnancy rates.

The influence of gender, age, education and household size on meal preparation and food shopping responsibilities

OBJECTIVE To examine the extent to which the gendered division of labour persists within households in the USA in regard to meal planning/preparation and food shopping activities. DESIGN Secondary analysis of cross-sectional data. SETTING 2007-2008 US National Health and Nutrition Examination Survey. SUBJECTS Sub-sample of 3195 adults at least 20 years old who had a spouse or partner. RESULTS Analyses revealed that the majority of women and men reported they shared in both meal planning/preparing and food shopping activities (meal planning/preparation: women 54 % and men 56 %; food shopping: women 60 % and men 57 %). Results from multinomial logistic regression analyses indicated that, compared with men, women were more likely to take primary responsibility than to share this responsibility and less likely to report having no responsibility for these tasks. Gender differences were observed for age/cohort, education and household size. CONCLUSIONS This study may have implications for public health nutritional initiatives and the well-being of families in the USA.

Misuse of Odds Ratios in Obesity Literature: An Empirical Analysis of Published Studies

Odds ratios (ORs) are widely used in scientific research to demonstrate the associations between outcome variables and covariates (risk factors) of interest, and are often described in language suitable for risks or probabilities, but odds and probabilities are related, not equivalent. In situations where the outcome is not rare (e.g., obesity), ORs no longer approximate the relative risk ratio (RR) and may be misinterpreted. Our study examines the extent of misinterpretation of ORs in Obesity and International Journal of Obesity. We reviewed all 2010 issues of these journals to identify all articles that presented ORs. Included articles were then primarily reviewed for correct presentation and interpretation of ORs; and secondarily reviewed for article characteristics that may have been associated with how ORs are presented and interpreted. Of the 855 articles examined, 62 (7.3%) presented ORs. ORs were presented incorrectly in 23.2% of these articles. Clinical articles were more likely to present ORs correctly than social science or basic science articles. Studies with outcome variables that had higher relative prevalence were less likely to present ORs correctly. Overall, almost one‐quarter of the studies presenting ORs in two leading journals on obesity misinterpreted them. Furthermore, even when researchers present ORs correctly, the lay media may misinterpret them as relative RRs. Therefore, we suggest that when the magnitude of associations is of interest, researchers should carefully and accurately present interpretable measures of association—including RRs and risk differences—to minimize confusion and misrepresentation of research results.