Ten putative contributors to the obesity epidemic

Abstract

The obesity epidemic is a global issue and shows no signs of abating, while the cause of this epidemic remains unclear. Marketing practices of energy-dense foods and institutionally-driven declines in physical activity are the alleged perpetrators for the epidemic, despite a lack of solid evidence to demonstrate their causal role. While both may contribute to obesity, we call attention to their unquestioned dominance in program funding and public efforts to reduce obesity, and propose several alternative putative contributors that would benefit from equal consideration and attention. Evidence for microorganisms, epigenetics, increasing maternal age, greater fecundity among people with higher adiposity, assortative mating, sleep debt, endocrine disruptors, pharmaceutical iatrogenesis, reduction in variability of ambient temperatures, and intrauterine and intergenerational effects as contributing factors to the obesity epidemic are reviewed herein. While the evidence is strong for some contributors such as pharmaceutical-induced weight gain, it is still emerging for other reviewed factors. Considering the role of such putative etiological factors of obesity may lead to comprehensive, cause specific, and effective strategies for prevention and treatment of this global epidemic.

Figures

Figure 1

Association of infections with fat mass: Linear association between Quantitative Serological Index and percentage fat mass (top) and absolute fat mass (bottom). Reprinted with permission from Fernandez-Real et al 2007.

Figure 2

Mean maternal age for all births and first births in United States from 1970 – 2004.

Figure 3

Percentage change in birth rates by age of mother from 1990 to 2004 in the United States.

Figure 4

Univariate relationship between maternal age and prevalence of obesity in 9 and 10 year old girls. Derived from data reported by Patterson et al.20

Figure 5

Spousal Spearman rank order correlations for body mass index among 8,663 spouse pairs, categorized by length of cohabitation. Figure reprinted from Jacobson et al. (Jacobson et al. 2007), with permission.

Figure 6

The relationship between fewer hours of sleep per day (sleep debt) and the incidence of obesity from 1960 to the present. As average daily sleep times have decreased, the incidence of obese adults has increased. Data points adapted from (Terman et al. 1913; McGhie et al. 1962; Hammond 1964; Tune 1968; Tune 1969; Palmer et al. 1980; Hicks et al. 2001; Punjabi et al. 2003); National Sleep Foundation Polls 1995, 1998 – 2002, 2005; and CDC Polls 1962, 1974, 1980, 1994, 2000, 2002, and 2004.

Figure 7

Four proposed mechanisms for endocrine disruptor function. ER, estrogen receptor; E2, estradiol; T, testosterone, P450s, cytochrome P450 aromatases which convert testosterone to estradiol; ED, endocrine disruptors; NR, nuclear receptors; 1–4, four possible mechanisms for endocrine disruptor function. Mechanism 1 corresponds to enhanced gene transcription by estradiol via endocrine disruptors; mechanism 2 to supressed transcription by estradiol via endocrine disruptors, mechanism 3 to suppresion of converstion of testosterone to estradiol by endocrine disruptors, and mechanism 4 to the enhancement of testosterone to estradiol by endocrine disruptors.

Figure 8. Percent of adults 18 years of age and over reporting antidepressant use in the past month by age and sex: United States, 1988–94 and 1999–2000

National Center for Health Statistics (2004). Health, United States, 2004 with chartbook on trends in the health of Americans. Hyattsville, MD, p 59.

Figure 9

Hermann RC, Yang D, Ettner SL, Marcus SC, Yoon C, Abraham M. Prescription of antipsychotic drugs by office-based physicians in the United States, 1989–1997. Reprinted with permission from Psychiatric Services. 2002;53(4):425–430.

Figure 10

Figure Percentage of homes with air conditioning. From US DOE, http://www.eia.doe.gov/emeu/consumptionbriefs/recs/actrends/recs_ac_trends_table2.html>.

Figure 11

Prevalence of putative contributors against the increasing prevalence of obesity. a) prevalence of obesity (CDC), b) mean age of mothers at first birth (NCHS, 2003), c) percentage of homes using air conditioning (Energy Information Administration), d) Patient visits involving Antipsychotic prescriptions (Olfsen et al, 2006), e) Glitazone prescriptions (IMS Health), f) PBDE in breastmilk (Noren et al, 2000; Guvenius et al, 2003), g) Average hours of sleep per night (data points from Terman and Hocking 1913; Hammond 1964; McGhie and Russel 1962; Tune 1968; Hicks et al 2001, Palmer et al 1980; NSF 2000, 2001, 2002, and 2008; Punjabi et al 2003).