Chemical toxins: a hypothesis to explain the global obesity epidemic

THE JOURNAL OF ALTERNATIVE AND COMPLEMENTARY MEDICINE
Volume 8, Number 2, 2002, pp. 185–192
Mary Ann Liebert, Inc.
Chemical Toxins: A Hypothesis to Explain the PAULA F. BAILLIE-HAMILTON, M.B., B.S. D.Phil.
ABSTRACT
The number of obese people worldwide has escalated recently, revealing a complex picture of significant variations among nations and different profiles among adults and children, re-gions, and occupations. The commonly held causes of obesity—overeating and inactivity—donot explain the current obesity epidemic. There is evidence of a general decrease in food con-sumption by humans and a significant decline in their overall levels of physical activity. Thereis also more evidence to indicate that the body’s natural weight-control mechanisms are notfunctioning properly in obesity. Because the obesity epidemic occurred relatively quickly, it hasbeen suggested that environmental causes instead of genetic factors maybe largely responsible.
What has, up to now, been overlooked is that the earth’s environment has changed signifi- cantly during the last few decades because of the exponential production and usage of syntheticorganic and inorganic chemicals. Many of these chemicals are better known for causing weightloss at high levels of exposure but much lower concentrations of these same chemicals have pow-erful weight-promoting actions. This property has already been widely exploited commerciallyto produce growth hormones that fatten livestock and pharmaceuticals that induce weight gainin grossly underweight patients.
This paper presents a hypothesis that the current level of human exposure to these chemicals may have damaged many of the body’s natural weight-control mechanisms. Furthermore, it isposited here that these effects, together with a wide range of additional, possibly synergistic,factors may play a significant role in the worldwide obesity epidemic.
INTRODUCTION
cling, the main causes are thought to beovereating and a lack of physical activity (Bray health care concern that affects adults andchildren in all socioeconomic groups (Bun-dred et al., 2001; Flegal et al., 1998). Although WHY THE OLD EXPLANATIONS ARE
there are many theories about the causes of to- NOT VALID
day’s obesity epidemic, to date, there is stillmuch uncertainty about obesity’s etiology. Al- though many non–lifestyle factors are known Overeating has been suggested as an impor- to influence weight, such as genetic predispo- tant cause of modern obesity, particularly be- sition, carbohydrate craving, and weight cy- cause highly palatable convenience foods are Occupational and Environmental Health Research Group at Stirling, Stirling University, Stirling, Scotland.
BAILLIE-HAMILTON
much more prevalent (Prentice and Jebb, 1995).
problem can effectively be ruled out (Prentice However, despite a general increase in the in- take of these foods, evidence suggests that, al- However despite the stability of the human though there is a perception among members gene pool, many largely genetically deter- of the general public that people are consum- mined, underlying controlling mechanisms that ing more calories in modern times, overall lev- set body weight and metabolic efficiency (e.g., els of daily caloric consumption have declined hormones, neural pathways, various brain nu- substantially thoughout the twentieth century.
clei, and many neurotransmitters), appear to be (Department for Environment, Food and Rural malfunctioning frequently in patients who are obese (Baptista, 1999; Harris, 1990; Wang et al.,2001). If genetic alterations are not responsiblefor such changes in metabolic functioning, per- haps there is another cause for them. Indeed, it Because a fall in food intake obviously would has been suggested that perhaps they have been not account for an increase in the incidence of caused by some environmental factor or factors obesity, it may be that that the modern seden- tary lifestyle is mainly responsible (Prenticeand Jebb, 1995). However, despite the adventof television, motorized transport, and energy- ARE ENVIROMENTAL CHEMICALS
saving domestic appliances (which has re- RESPONSIBLE?
sulted in an overall reduction in manual labor) Toxic chemicals and their effects on weight since the middle of the twentieth century, hardevidence does not show that levels of physical Although diet and behavioral changes have activity have plummeted sufficiently to cause been considered to be major causative factors, such a high incidence of obesity during this it is difficult to see how they could produce time period (Morris, 1995; Rasvussin, 1995). In- many of these metabolic malfunctions.
deed, a report by the British Sports Council However, the levels of certain substances— (now known as Sport England), London, Eng- synthetic organic/inorganic chemicals–in the land, on physical activity noted the opposite environment have coincided with the increas- phenomenon, stating that “participation is in- ing incidence of obesity that has been docu- creasing across all age bands and all social mented. These substances are known to dam- groupings” (Sports Council, 1993).
age many of the mechanisms involved inweight control.
Since the creation, and subsequent introduc- tion, of synthetic organic/inorganic chemicals Weight control is not simply about energy in- in the late nineteenth century, the global com- take and energy expenditure; these comprise a munity has been increasingly exposed to an ex- superficial part of a very complex situation ponential rise in the production of these sub- (Miller and Mumford, 1966). Body weight is stances (see Figure 1; Flegal et al., 1998; United generally thought to be homostatically regu- States Tariff Commission, [various documents] lated at a certain predetermined level or “set 1918–1994). In their daily lives, human beings point” by, largely genetically determined, feed- are now exposed to tens of thousands of these back-control mechanisms that enable the body chemicals, in the forms of pesticides, dyes, pig- to maintain a stable weight for relatively long ments, medicines, flavorings, perfumes, plas- periods of time (Harris, 1990). Because of the tics, resins, rubber-processing chemicals, inter- genetic basis posited for these mechanisms, the mediate chemicals, plasticizers, solvents, and “set point” theory has not been widely used to surface-active agents (United States Tariff explain today’s incidence of obesity, which has Commission, [various documents] 1918–1994).
occurred over a relatively short period of time.
Pesticide residues, preservatives and additi- Thus, dramatic changes in the gene pool that tives are ingested with foods and contaminated would have been sufficient to cause the current water, inhaled from polluted indoor and out- DO CHEMICAL TOXINS CAUSE OBESITY?
plain why the scale of this chemically causedweight gain has effectively been “missed,” bysome researchers.
industrial chemicals produce weight gain.
These chemicals—which human beings are ex-posed to quite regularly—include: Pesticides, for example, organochlorines, suchas dichlorodiphenyltrichloroethane (DDT),endrin, lindane, and hexachlorobenzene(Chadwick et al., 1988; Deichmann et al., 1972;Deichmann et al., 1975; Dorgan et al., 1999;Hovinga et al., 1993; Stellman et al., 1997;Takahama et al., 1972; Villeneuve et al., 1977) The production of synthetic organic chemicals and the percentage of overweight adults in the United States during the twentieth century. The illustration is Cranmer et al., 1978; Nicolau, 1983; Tran- taken from The Detox Diet, by Paula Baillie-Hamilton, M.B., B.S. D.Phil. (to be published by Penguin Books, Lon-don, in April 2002). Carbamates, including dithiocarbamates(Walker et al., 1994; Yen et al., 1984)Polychlorinated biphenyls (Clark, 1981; Dar door air, and absorbed cutaneously via per- sonal-care products. As a result, the average person now has many hundreds of industrial monly used as fire retardants (Gupta et al., chemicals lodged in his or her body, with many of these toxins being transferred across the fe- Plastics, such as phthalates and bisphenol A tal–maternal blood barrier (Jacobson and Jacob- (Ashby et al., 1999; Ema et al., 1990; Field et son, 1996). Many of these toxins are also ap- al., 1993; Howdeshell et al., 1999; Lamb et al., pearing in women’s breast milk, thus, probably transferring their effects to children who are breast fed (Alleva et al., 1998; Bordet et al., 1993).
(Antonio et al., 1999; Hovinga et al., 1993) One of the toxic effects of these chemicals ap- Solvents (Chu et al., 1986; Gaworski et al., pears to be weight gain. Unlike the well-known 1985; Hardin et al., 1987; Moser et al., 1995; weight loss resulting from high exposure to toxins, this weight gain tends to occur at muchlower levels of exposure, which fail to make an- The example of organochlorine pesticides: imals or humans obviously ill (Takahama et al., 1972). However, as a result of a long-held ideain some cultures that weight gain must be ev- The organochlorine pesticides illustrate how idence of “good health,” a significant amount chemotoxicity can promote weight gain. Be- of evidence showing these chemicals to cause cause of previous extensive usage as pesticides, weight gain has been virtually ignored, ex- inherent structural stability, persistence in plained away, or even, on occasion, apologized body systems, and ability to concentrate in an- for (Lamb et al., 1987; Takahama et al., 1972).
imals that are higher up on the food chain, Although it has been generally accepted, in many organochlorine pesticides are currently recent years, that weight gain can be evidence present in human fat in relatively high levels of chemotoxicity, much of the evidence pre- (Hovinga et al., 1993; Stellman et al., 1997).
sented in earlier scientific papers was rarely mentioned in their abstracts. Being that current duced weight gain appears to come from in- creases in the overall proportion of body fat. In formation contained in abstracts, this may ex- one animal study, the pesticide dieldrin more BAILLIE-HAMILTON
than doubled the total body-fat content of the monoamine hormones it produces (nora- treated mice (Deichmann et al., 1972). Another drenaline, dopamine, adrenaline), plays a key role in controlling weight, body-fat levels, and known as lindane, induced obesity in animals nutrition partitioning (Bray, 1993). The sympa- (Chadwick et al., 1988). Indeed, in yet another thetic nervous system may do this by suppress- study, the overall weight-gain effect of another ing appetite, particularly the appetite for fats pesticide, hexachlorobenzene, appeared to be (Leibowitz, 1992); by enabling the body to mo- so powerful that a group of treated animals still bilize fat stores for use (Hamann et al., 1998; Pao- managed to gain significantly more weight— letti et al., 1961); and by stimulating physical ac- despite the fact that their food intake was cut tivity levels powerfully (van Praag et al., 1990).
by 50%—than untreated controls who were on Thus, it is not surprising that abnormalities in full food rations (Villeneuve et al., 1977).
the sympathetic nervous system are very com- mon in most forms of obesity (Dulloo and Miller, thetic and industrial chemicals, appear to cause 1986). Indeed, most of the drugs commonly used weight gain by interfering with most of the dif- to treat patients who are obese, or who have eat- ing disorders, primarily alter these patients’ weight control system. In particular, these monoamine hormones levels. (Leibowitz, 1992).
Unfortunately, many of the commonest syn- thetic chemicals in the environment appear to Disrupt the major weight controlling hor- target the sympathetic nervous system. This mones, such as catecholamines, thyroid hor- can lower its effectiveness dramatically, not only in the short term but also permanently (Goldman et al., 1997; Knoth-Anderson and Abou-Donia, 1993; Seegal et al., 1994). One Alter levels of, and sensitivity to, neuro- study of pesticide factory workers, revealed transmitters (in particular dopamine, nor- that those who were exposed to pesticides ex- creted 50% more catecholamines then control workers. Another study showed that pesticide (nerve and muscle tissue in particular), often DDT, organophosphates, and carbamates had at levels that human beings are currently ex- plasma levels of adrenaline and noradrenaline that were approximately 40% and 20% (re-spectively) lower than nonexposed individuals This interference results in changes in ap- (Embry et al., 1972; Richardson et al., 1975).
petite; food efficiency; and fat, carbohydrate,and protein metabolism. The desire, and ability, to exercise are also affected. These changes havebeen thought to be responsible for increases in The ability to manipulate the underlying sys- body weight (Chadwick et al., 1988; Gupta et al., tems that control body weight has resulted in 1983; Howdeshell et al., 1999; Moser et al., 1995; many synthetic chemicals being used by the Pearson & Dutson, 1991; Takahama et al., 1972; agricultural community to promote animal fat- Trankina et al., 1985; Yen et al., 1984).
tening and growth. These substances, generallyknown as growth promoters, include such syn-thetic chemicals as antithyroid drugs, corticos- Effects of toxic chemicals on the sympathetic teroids, anabolic steroids, organophosphate pesticides, carbamates, antibacterials, and To illustrate this, it is worthwhile to consider ionophores (Pearson & Dutson, 1991; Trankina the effects of many toxic chemicals on what is et al., 1985; Yen et al., 1984). Although many of possibly the key weight-controlling system (the these substances are now illegal for use as sympathetic nervous system (Bray, 1993). The growth promoters, they still are consumed in sympathetic nervous system, in conjunction with foods that human beings eat because this prac- DO CHEMICAL TOXINS CAUSE OBESITY?
tice has not been stopped effectively. Similar portedly found a positive association between chemicals also are retained in foods as pesticide levels of certain toxic chemicals in the chil- or chemical residues (Pearson & Dutson, 1991).
drens’ and adults body tissues and increased Many treated nonfood products also confer ex- body weight in these subjects (Dar et al., 1992; posure to human beings (Alleva et al., 1998).
Hovinga et al., 1993; Schildkraut et al., 1999;Stellman et al., 1997).
Therefore, it can be posited that the relatively recent presence of synthetic chemicals in the Synthetic chemicals are heavily used in med- environment may be a significant causative fac- icine to treat certain illnesses because such tor in the current worldwide obesity epidemic.
chemicals can strongly alter hormone systems, These chemicals may be causing weight gain levels of neurotransmitters, and other aspects via toxic effects on the body’s natural weight- of general body metabolism. Not surprisingly, control mechanisms. The very speed of the in altering these systems, synthetic chemicals marked increases in the numbers of overweight can effectively alter the weight set point. This people, as clearly shown in Figure 1, indicates has resulted in their previous usage for pro- that changes in the environment are more likely moting weight gain in patients with anorexia to be the source of the obesity epidemic than (Morley, 1996). And more evidence that syn- thetic chemicals promote weight gain in hu- While a link between human exposure to ever- mans arises from the extremely high number greater numbers and amounts of synthetic chem- of synthetic pharmaceuticals that make pa- icals, which are known to promote weight gain, tients gain weight, an obviously unwanted has not yet been established, the coincidence of side-effect. Such pharmaceuticals include some the obesity epidemic with the appearance of medicines commonly used in cardiology, on- these chemicals in the environment indicates the cology, psychiatry, and immunology (Baptista, possibility of a causative relationship.
1999; Chrysant et al, 1991; Simpson et al, 2001; The idea that many toxic chemicals in foods and the environment have, in effect, poisoned the body’s natural weight-control mechanismswould help to explain many of the functionaldifferences found in the weight-control sys- SUMMARY OF THE HYPOTHESIS
tems of patients who are obese (Wang et al.,2001). This concept would also explain the in- Being that the levels of synthetic chemicals congruity of continuing weight gain in hu- required to cause weight gain are relatively low mans despite falling food intakes and no ex- and that they have been administered deliber- cessive reductions in exercise. The concept also ately to livestock and patients to produce this may shed light on the marked failure of food- effect, it may well be that nondeliberate expo- restriction diets to effect long-term weight loss.
sure to low levels of contaminants in food and The extent to which each individual is affected the environment could have similar results.
could also be significantly related to a given This would not be too surprising because, de- individual’s genetic ability to deal with these spite being generally many times less potent than natural hormones, many environmental The high levels of chemotoxins shown to be contaminants with endocrine-disrupting prop- present in human fat and breast milk, the ease erties are currently present in wildlife, in labo- of transfer through the fetal-maternal blood ratory animals, and in living human tissues at barrier and the increased sensitivity of devel- concentrations that are thousands of times oping systems to these toxins may also help to higher than the natural hormones they are de- explain the increasingly early age at which this signed to mimic (Alleva et al., 1998).
problem is evident in infants and children and Evidence that this could be the case comes the increasing extent to which individuals are from several studies of adults and children in now affected (Alleva et al., 1998; Bundred et al., free-living populations. Researchers have re- BAILLIE-HAMILTON
Research is now needed to investigate which weight and obese children between 1989 and 1998: Pop- of the many chemicals in the environment are ulation based series of cross sectional studies. BMJ probably causing the greatest damage to the Chadwick RW, Cooper RL, Chang J, Rehnberg GL, McEl- human weight-control system. A possible way roy WK. Possible antiestrogenic activity of lindane in to move forward would be to study the effects female rats. J Biochem Toxicol 1988;3:147–158.
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farmers who farm conventionally or people Clark DR. Bats and environmental contaminants: A re- who work with plastics and pharmaceuticals to view. U.S. Department of the Interior [Special Scientific Report # 235]. Washington D.C: Fish and Wildlife Ser-vice, 1981:1–29.
Cranmer JS, Avery DL, Grady RR, Kitay JI. Postnatal en- docrine dysfunction resulting from prenatal exposure ACKNOWLEDGMENTS
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