**3.1 Obesity**

*Environmental Issues and Sustainable Development*

**3. Consequences of exposure to EDCs**

*EDCs interfere with the action of hormones.*

the most complicated situations to investigate.

*EDCs can contribute to a variety of dysfunctions and diseases.*

The endocrine system is a complex network of glands (or tissues), hormones, and receptors controlling different functions and insuring the homeostasis of the organism. EDCs pose a threat to humans. They alter the homeostatic systems through environmental or developmental exposures. By interfering with hormonal functions, EDCs can contribute to a variety of dysfunctions and diseases. Every endocrine axis may be the target of EDCs. Exposure to EDCs (*in utero* or lifetime) may be a significant component of the environmental origin of several medical conditions including obesity, diabetes, reproductive disorders, and cancers (**Figure 3**) [1–4, 10–46]. A specific EDC may be innocuous by itself but when associated with other EDCs may cause hazardous effects (cocktail effects). The EDC mixtures are

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**Figure 3.**

**Figure 2.**

Obesity is a worldwide pandemic associated with increased morbidity/mortality and high cost for the society [50–52]. Although alterations in food intake and/or decrease in exercise are important contributing factors to obesity, they cannot fully explain the current obesity pandemic. Obesity pandemic coincides with the marked increase of the chemicals in the environment over the past 60 years.

Some EDCs can impair regulation of adipose tissue and food intake, reduce basal metabolic rate, and predispose to weight gain and obesity despite normal diet and exercise. They can also cause resistance to weight loss if subjects are on anti-obesity diet and/ or drug. These EDCs are called obesogens (or metabolism-disrupting chemicals) [2, 4, 10, 12, 15–20, 26–33, 36]. The list of obesogens is continuously growing. Approximately 50 chemicals have been implicated. They include monosodium glutamate, nicotine, bisphenol A, phthalates, parabens, and tributyltin (non-exhaustive list).

Obesogens have several target tissues including adipose tissue, brain, liver, stomach, and pancreas. At the level of adipose tissue, obesogens promote obesity by inducing an increase in the number of adipocytes (by activating nuclear receptor signaling pathways critical for adipogenesis) and storage of fat (**Figure 4**) [17].

Perinatal exposure to obesogens is associated with overweight and obesity in children. Some obesogens (e.g., bisphenol A and tributyltin) are able to induce heritable changes that are propagated through multiple generations without any new exposure (transgenerational inheritance) [17].

White adipose tissue is an important reservoir of lipophilic obesogens (many obesogens are lipophilic chemicals). Rapid weight loss increases plasma levels of lipophilic obesogens and may contribute to weight cycling (yo-yo effect).

The dramatic increase in the prevalence of obesity, especially among children, shows that intervention actions are needed urgently. Exposure to obesogens should be reduced or avoided especially in fetus and neonate.

**Figure 4.** *Obesogens alter lipid homeostasis to promote adipogenesis and lipid accumulation.*
