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Obesogens

Are the chemicals in your environment making you fat?

 

By Tamzyn Murphy Campbell

BSc, BSc Med(Hons) Human Nutrition and Dietetics, RD

 

South Africans rank third fattest in the world after the Americans and British, according to Compass Group Southern Africa’s 2011 report.[1] And while we all know that diet and lifestyle are largely to blame, few realise that insidious little fat-making molecules permeating our environment are making the battle against the bulge even harder.

 

FAT-INATORS

“[The obesity pandemic trend] is more akin to an infectious disease, a contagion, or some other mass environmental exposure [than]… purely a mass alteration in behaviour change” – Professor Lustig, paediatric endocrinologist at the University of California.[2]

Indeed, recent evidence indicates that various environmental hormone-disrupting chemicals increase the number of fat cells and their storage, thereby promoting obesity.[3] These obesogens can also boost appetite and reduce feelings of fullness, increasing the calories you consume.[2] Plus they can shunt the calories you eat into storage rather than allowing them to be burned as energy. [2] Exposure to obesogens in the womb and during early development could increase fat cell quantity for life and programme you for future obesity, even if the exposure is short-lived.[3]

Despite this field being so new, scientists know of at least 20 obesogens. Some of which have been found in 95% of the American population; implying that chemical exposure has the potential to affect most if not every member of a population.[4]

 

ESTROGENS

They’re everywhere. In our water, food and plastics. Possibly our biggest environmental estrogen exposures are DDT, bisphenol-A (BPA) and genistein.[2] DDT use as a pesticide has ceased worldwide with a few exceptions. However, it’s still used indoors in countries including South Africa to reduce malaria.[5] DDT is detrimental to health, specifically reproductive health and has been implicated in diseases like cancer.[6] In the US, where it’s been banned since 1972, DDT’s metabolite DEE is still being found in pregnant women’s urine, even in those born after 1972. Pregnant women’s urine-DEE concentration predicts the weight of their children at age three.[2]

BPA (in hard plastic bottles numbered ’7’, babies’ bottles and toys and the plastic lining of tins) is also linked to cancer, reproductive changes,[7] fat cell production and increased adult body mass index (BMI).[2]

Newborn rats given genistein (from soya and alfalfa) were fatter at age three and four months. It’s not known whether genistein contributes to human obesity. Though it’s possible the large amount of soya commonly found in our food supply is cause for concern.[2]

 

OTHER OBESOGENS

  • Pthalates are plasticisers that make plastics soft and pliable and have a distinctive new-plastic smell. They’re in hundreds of products from cling wrap and beverage bottles[8], to shower curtains, raincoats and children’s rubber duckies. [9],[2] They’re even in personal care products[9]. Everyone’s contaminated. Recently, urine phthalate levels have been linked to increasing waist circumference[2]
  • Atrazine and other organochlorines Atrazine is a widely used pesticide and it’s teratogenic, meaning it causes malformations during pregnancy. Blood atrazine levels are linked to fat stores and insulin resistance in adults[2]
  • Tributylins (TBT) and other organotins TBT is used to paint boats’ hulls to keep them barnacle free. So it’s also in our general water supply. TBT tells fat cells to multiply, boosts dangerous belly fat (via the hormone cortisol), and promotes fatty liver in infant rats whose pregnant moms were exposed to TBT once. Scientists know we’re exposed to TBT because it’s found in our urine, but still need to confirm if it’s a primary cause of human obesity[2]
  • Cigarettes and air pollution are both linked to weight gain and obesity in studies. In children, thiocyanate (cyanide’s cousin) from second-hand cigarette smoke reduces thyroid hormone levels (responsible for metabolism). And traffic within 150 miles of a child’s home appears to increase BMI at age 18.[2]

 

DAMAGE CONTROL

If you’ve been exposed to obesogens, particularly before puberty, your metabolism’s adjusted to be more efficient at storing fat. So, is this an excuse to give up your lifelong weight battle? Dr Bruce Blumberg, professor of developmental and cell biology at the University of California, Irvine, who coined the term ‘obesogen’ back in 2006, says that exposure doesn’t ensure obesity. It just means you have to try a little harder.[4]

It’s probably best to copy Dr Blumberg’s strategy to minimise his and his family’s obesogen exposure: reduce plastic in your life; avoid sugar (for more on this read Lustig article on page X) and processed, canned and packaged food; and eat organic, fresh, home-made food whenever possible. [4]

 

References include

[1] South African Institute of Race Relations. Press Release. African women and white men weigh in heaviest. Feb 2013

[2] Lustig RH. Fat Chance. Hudson Street Press, London, England. Jan 2013

[3] Grun F, Blumberg B. Endocrine disruptors as obesogens. Mol Cell Endocrinol. May 2009;304(1-2):19-29 http://www.ncbi.nlm.nih.gov/pubmed/19433244

[4] Ahearn A. What do we know about obesogens? with Bruce Blumberg. Environmental Health Perspectives. Jul 2012;120. Published online http://ehp.niehs.nih.gov/july-podcast/

[5] South Africa.info. WHO follows SA’s lead on DDT. Sep 2006 http://www.southafrica.info/about/health/malaria-190906.htm#.UahjMECmg1I

[6] US Environmental Protection Agency. Persistent Bioaccumulative and Toxic (PBT) Chemical Program. DDT. Apr 2011 http://www.epa.gov/pbt/pubs/ddt.htm

[7] Breast Cancer Fund. Bisphenol A (BPA). May 2013 http://www.breastcancerfund.org/clear-science/chemicals-glossary/bisphenol-a.html

[8] Sax L. Polyethylene terephthalate may yield endocrine disruptors. Environ Health Perspect. Apr 2010;18(4):445-8  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2854718/pdf/ehp-118-445.pdf

[9] Centers for Disease Control and Prevention. Factsheet: Pthalates. Apr 2012 http://www.cdc.gov/biomonitoring/Phthalates_FactSheet.html