Obesity: Why are we getting fat? :epizza:

[Michaelangelica]

Interesting how scientific studies that don't conform to certain peoples pet theories never make it here.

 

Increased Food Intake Alone Explains Rise In Obesity In United States, Study Finds

 

 

I seem to remember saying the same exact thing and being accused of being prejudice against obese people and also being called over simplistic.

Good Nitack; so make it your job to find and post such articles.

 

It is also interesting that you didn't mention the "related stories" at the same website

Related Stories

Fructose Metabolism By The Brain Increases Food Intake And Obesity, Review Suggests (Mar. 26, 2009) — Scientists have built on the suggested link between the consumption of fructose and increased food intake, which may contribute to a high incidence of obesity and type 2 ... > read more

Significant Amount Of Binge Eating Occurs In Restaurants (Oct. 26, 2006) — Contradicting the common perception that binge eating is typically done in private, a significant amount of bingeing occurs in restaurants -- according to a recent study published in the November ... > read more

Salt Intake Is Strongly Associated With Obesity (Nov. 13, 2006) — The study reports that increasing intakes of sodium (salt) obligatorily produce a progressive increase in thirst. The progressive increase in the average intake of salt explains the observed ...

Hormone Found To Decrease Appetite And Increase Activity (Apr. 26, 2006) — New research shows how topping up the levels of a hormone found in the gut could help reduce the appetite and increase activity in overweight and obese ... > read more

Metabolic Defect In Liver Can Lead To Obesity (July 26, 2007) — Researchers have identified a genetically-transmitted metabolic defect that can lead to obesity. The defect involves decreased production of liver enzymes needed to burn fat and may help to explain ... >

[Michaelangelica]

We humans have about 98 enzymes that can break down carbohydrates. The bacteria in our gut have over 240 enzymes to turn carbohydrates into energy.

In fact, if it wasn't for the single-celled creatures in our gut, we'd all be a lot thinner.

 

In one study, mice were delivered by Caesarean section in sterile conditions, so they had no bacteria (or their little friends) living in their gut. The mice were then raised in sterile environments, and fed only sterile food.

 

Compared to their 'regular' germ-laden siblings (who were fed the same food), they ate 29 per cent more and yet, were very skinny, carrying 42 per cent less fat.

 

And then, when their mice guts were colonised with the single-celled creatures of their 'regular' siblings, they simultaneously ate less and got fatter.

 

Back in the old days, when food was hard to come by, having bacteria in your gut was an advantage. They would help you extract extra calories from the food. And both you and the bacteria would benefit.

 

But these days, food is easy to come by. Even so, there are some people who swear blind that they eat hardly anything, and yet put on weight.

 

If that's true, maybe they just have super-efficient bacteria, wringing those extra calories out of their diet.

We are more microbe than man › Dr Karl's Great Moments In Science (ABC Science)

[Michaelangelica]

Fatty foods, not empty stomach, fire up hunger hormone

11 Jun 2009

 

New research led by the University of Cincinnati (UC) suggests that the hunger hormone ghrelin is activated by fats from the foods we eat – not those made in the body – in order to optimise nutrient metabolism and promote the storage of body fat.

 

The findings, the study's author says, turn the current model about ghrelin on its head and point to a novel stomach enzyme (GOAT) responsible for the ghrelin activation process that could be targeted in future treatments for metabolic diseases.

 

The laboratory study, led by Matthias Tschöp, MD, UC associate professor of psychiatry and internal medicine, is published online ahead of print 5 June 2009 in the journal Nature Medicine.

 

Ghrelin is a hormone that was believed to accumulate during periods of fasting and is found in the body in high concentrations just before meals.

It is dubbed the "hunger hormone" because it has been shown that administration of pharmacological doses acts in the brain to stimulate hunger and increase food intake in animal models and humans.

 

The ghrelin hormone is unique in that. . .

. . .

• When exposed to certain fatty foods, mice with more GOAT gain more fat," says Tschöp.
  
• "Mice without GOAT gain less fat since their brain does not receive the 'fats are here, store them' signal."
  

Fatty foods, not empty stomach, fire up hunger hormone - News

[Michaelangelica]

(NaturalNews) Phthalates used in food packaging could be linked to childhood obesity, according to two recent studies conducted by the Mount Sinai School of Medicine that included research conducted on more than 900 children in East Harlem and surrounding communities. The studies have added to a growing body of evidence that link phthalates to health problems.

 

One of the studies, according to the Mount Sinai researchers, focused on 400 girls in the East Harlem community. The results showed that the heaviest girls had the highest levels of phthalates metabolites in their urine.

 

Another significant research project called Growing Up Healthy in East Harlem examined the diet and other factors for 520 East Harlem children aged 6-8 with the results indicating that the level of phthalates in the children tested was higher than the national average.

Packaging Chemical Linked to Childhood Obesity

phthalates are compounds based on PHTHALIC ACID (generated via phthalic anhydide). Various side chains (shown here as purple spheres) project from each carboxyl group. Phthalates are commonly used to soften plastics and concerns have been voiced about their potential to cause cancer or mimic hormones.

phthalates: image of generic phthalate molecule by Russell Kightley Media

 

Scientists are aware that BPA and phthalates are environmental estrogens.

But they don’t agree on how much is a harmful dose. The industry conducted animal studies looking for cancer. Acceptable limits are based on the dose causing cancer in those animal studies.

. . .

Congress, through the Consumer Product Safety Commission, is banning phthalates from products sold for use by children under 12 as of August, 2009. This includes baby bottles and pacifiers.

. . .

Therefore, let the buyer beware. Avoid beverages in plastic bottles (#1, 3, or 7 on the bottom, if you want to check).

Especially, avoid allowing the full bottles to get warm, a condition in which the chemical is more likely to leach.

In addition, avoid drinking soda from such bottles because the acid will leach the chemical out. And avoid warming food in the microwave in plastic containers.

Chemicals in Plastic Water and Soda Bottles Emasculate Boys | ModernHealthyLiving.com

 

Lancaster, Pa.: Would you please explain the chemicals that leach out of plastic? I am concerned about the thicker type of plastic that leaves no taste. Thank you.

 

Laura Moser:

Different plastics leach different chemicals; some to a far greater degree than others. Until questions arose about Bisphenol A leaching, durable #7 polycarbonate was considered completely safe.

People worried mostly about phthalates leaching from bendy PVC plastics, particularly those labeled #3.

Now, it seems that diethylhydroxylamine phthalates might also leach from #1 PETE plastics after repeated use.

The FDA disputes this claim, but I'm afraid my confidence in that agency isn't what it used to be.

Laura Moser takes readers' questions on the*bottled-water debate. - - Slate Magazine

 

And that faint lavender scent as I shampoo my hair? Credit it to phthalates, molecules that dissolve fragrances, thicken lotions, and add flexibility to PVC, vinyl, and some intravenous tubes in hospitals.

The dashboards of most cars are loaded with phthalates, and so is some plastic food wrap.

Heat and wear can release phthalate molecules, and humans swallow them or absorb them through the skin. Because they dissipate after a few minutes to a few hours in the body, most people's levels fluctuate during the day.

 

Like bisphenol A, phthalates disrupt reproductive development in mice. An expert panel convened by the National Toxicology Program recently concluded that although the evidence so far doesn't prove that phthalates pose any risk to people, it does raise "concern," especially about potential effects on infants. "We don't have the data in humans to know if the current levels are safe," says Antonia Calafat, a CDC phthalates expert. I scored higher than the mean in five out of seven phthalates tested. One of them, monomethyl phthalate, came in at 34. 8 ppb, in the top 5 percent for Americans.

Leo Trasande speculates that some of my phthalate levels were high because I gave my urine sample in the morning, just after I had showered and washed my hair.

. . .

The compounds escape from treated plastic and fabrics in dust particles or as gases that cling to dust.

People inhale the dust; infants crawling on the floor get an especially high dose. Bergman describes a family, tested in Oakland, California, by the Oakland Tribune, whose two small children had blood levels even higher than mine.

When he and his colleagues summed up the test results for six different PBDEs, they found total levels of 390 ppb in the five-year-old girl and 650 ppb--twice my total--in the 18-month-old boy.

. . .

Mixed together, pesticides, PCBs, phthalates, and others "might have additive effects, or they might be antagonistic," says James Pirkle of the CDC, "or they may do nothing. We don't know. "

. . .

 

Plastic bottles, bags, and other products dumped into the environment are weathered and degraded, causing tiny fragments to break off.

 

Researchers have discovered substantial amounts of tiny plastic fragments on the ocean surface and on beaches, and also have identified plastic in the benthos.

 

In addition to particles, plastic pellets used to manufacture plastic goods are also present in the ocean.

 

Particles and pellets are mistaken for food by many marine org anisms, and the consequences of ingesting plastics are not well known.

 

Plastic in an aqueous medium can, however, absorb and accumulate polychlorinated biphenyls (PCBs) in levels much higher than ambient seawater.

 

We have been working on an investigation to determine if plastic pollution in the form of tiny particles and pellets is another source of PCBs for deposit-feeding holothurians.

http://opendoorworld.com/website/index.php?module=article&view=14&MMN_position=30:30

 

Physical and chemical properties

 

Both dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) are colourless liquids. DBP is an oily liquid with a weak odour. DEHP has almost no odour.

DBP

 

Melting point: 35°C

Boiling point: 340°C

Density/specific gravity: 1.043

Vapour density: 9.6

DEHP

 

Melting point: 50°C

Boiling point: 230°C at 5mm Hg

Density/specific gravity: 0.9861 at 20°C

Vapour pressure: 1.32 mm Hg at 200°C

Vapour density: 16 (air=1)

 

DBP is soluble in most organic solvents, but only slightly soluble in water. The flashpoint is 171° Celsius. DEHP is insoluble in water, miscible with mineral oil and hexane, and soluble in most organic solvents.

Common uses

 

Phthalates are manufactured chemicals that are commonly added as plasticisers to make plastics more flexible.

 

DBP is also used in elastomers, lacquers, explosives, printing inks, resin solvents, perfume oil solvents, paper coatings, adhesives, and nail polish. It is used as a solid rocket propellant.

 

DEHP is primarily used as one of several plasticisers in polyvinyl chloride resins, used for fabricating flexible vinyl products. It is used to detect leaks in protective face gear, and as a test material for filtration systems. It has also reportedly been used as a replacement for polychlorinated biphenyls (PCBs) in dielectric fluids for electric capacitors and in vacuum pumps.

Sources of emissions

Point sources

 

The primary sources of phthalate emissions are the industries that manufacture or use them in the production of chemicals and plastics.

DBP is also released from the manufacture of machinery and millwork. These emissions are primarily to the air, with a small percentage to the water and land.

Diffuse sources

 

DBP may be released from commercial and household use, disposal of paints and varnish, and manufacture of plastic parts and carpet backing. DEHP is distributed widely in the environment because of its diffuse use, volatility and persistence.

Natural sources

 

Phthalates may be produced naturally by some animals and plants, and by small organisms in soils.

Mobile sources

 

None expected.

Consumer products that may contain phthalates

 

DBP may be found in colognes and perfumes, cosmetics, paints undercoats and primers, plastic products, floor polish, window cleaning products, caulks and sealants, latex-type adhesives, resin and rubber adhesives, safety glass, vinyl floors, hairspray and nail polish.

 

DEHP is in polyvinyl chloride (PVC) plastic products like toys, vinyl upholstery, shower curtains, adhesives, and coatings.

It is used in some food packaging, and in medical product containers (including those for blood) and equipment.

It is also used in some inks, pesticides, cosmetics and vacuum pump oil.

Health effects

http://www.environment.gov.au/atmosphere/airquality/publications/sok/phthalates.html

[Michaelangelica]

A quick cure?

 

[Nitack]

A quick cure?

 

 

I fail so see the relevance.

[Michaelangelica]

It looks like someone reads this thread

What Causes Obesity In Austraila, U.K and America

PostDateIcon March 11th, 2009

 

What causes obesity? Well, obesity is not caused by the "big 2" - overeating and no exercise alone…..Obesity is multifactorial in origin.

. . .

 

Obesity refers to a state of a person’s bodyweight when it’s 20% or more above normal bodyweight.

. . .

It’s not just a health hazard, it’s a life threatening disease as well.

. . .

 

But there’s also other causes - other than the "big 2" - "no exercise and overeating", that contribute to obesity.

 

Not Enough Sleep is What Causes Obesity

. . .

 

The Americans slept an average of 8.5 hours per night in 1960. In a 2002 poll by the National Sleep Foundation, the

average hour had decreased to less than 7 hours per night.

 

The results show that the decreased hours of sleep was partly associated with the increase in obesity.

 

Prenatal Effects Are What Causes Obesity

 

In the study for mice during pregnancy, offsprings of mice fed with high-fat food are more likely to become fat than offsprings of mice fed with normal food.

 

 

Fat Equals Fecund - This Is What Causes Obesity

 

If you’re fatter, chances are you’ll have more children.

. . .

Does having more children cause women to gain weight or does being overweight or obese cause women to produce more children?

Answer is probably both.

 

 

Older In Age is What Causes Obesity

 

. . .

 

The most probable reason?

 

Ah…Sigh….Due to decrease in your metabolism……

 

. . .

Temperature Effects Cause Obesity

 

. . .

Less Smoking Or Quitting Smoking Causes Obesity

 

…..Most likely is because nicotine is an appetite suppressant and seemingly can raise your metabolic rate…..

 

T. . .

 

 

Pollution Can Cause Obesity

 

. . .

we’re exposed more to pollutants like industrial chemicals (dyes, plastic wastes, pesticides, herbicides, gaseous compound, solvents….).

 

There’s evidence that a small amount of some of these chemicals can lead to weight gain. Studies have found that when people are exposed to these chemicals found in food, the higher the toxic level in the food, the greater the body weight.

 

This is because some of these chemicals are endocrine disruptors that disrupt the functions of hormones like oestrogen.

 

You know right, when your hormone (oestrogen) does not function well, it wreaks havoc in your body, including weight gain?

 

Drug Use Is What Causes Obesity

 

Some drugs have ugly side effects - one of the most common ones - weight gain.

. . .

 

Well, drug for high blood pressure, is one.

 

Drugs to treat HIV, is another.

 

Endometriosis drugs to treat endometriosis, is a classic example that can fatten you up.

 

Contraceptive pills will pile pounds on you.

 

Diabetes medications will pad you out…..

 

…..

First Child In Older Women - A Cause For Obesity

 

The mean age of women giving first birth in the US has increased from 21.4 in 1970 to 24.9 in 2000.

 

Could poor sleep cause this? Probably.

 

Also, as family size decreases, first-borns make up for a greater share of the population - evidenced in the US wherein in 1976, 9.6% of women in their 40s had one child but in 2004, the percentage had increased to 17.4%. This combination of older women and more single children could be contributing to the obesity epidemic.

Like Marrying Like - A Cause For Obesity

 

. . .

 

If you’re thin, you’re more likely to marry a thin person and if you’re fat, you’re more likely to marry a fat person…..

 

 

On its own, this would not account for the increase in obesity but if we include other factors such as genetics and obese people produce more children, they could amplify the increase in obesity from other causes.

 

In conclusion, obesity isn’t due to a single cause but is multifactorial in origin.

 

The causes discussed here are by no means exhaustive……

 

You could have other causes like genetics, overeating, slower metabolism, gender, illness, psychological factors, diet rich in simple carbohydrates, frequency of eating…….

 

S-o-o-o-o,

 

Can you then jump in glee because "no exercise and overeating" are not the only major causes of obesity? Since you hate to exercise and like to eat? (Aren’t we all?)

. . .

By Cecelia Yap

Published: 1/9/2007

 

What Causes Obesity In Austraila, U.K and America | 101 Tips On Weight Loss

 

 

 

Is Phentermine Safe Dieting?

 

There is no doubt that phentermine is an effective agent to help lose weight. However, there are a lot of debate about the safety of the drug. Unlike many of the negative hype that has received the medication, phentermine, as required when they are, is actually a safe way to lose unwanted weight.

Is Phentermine Safe Dieting? | Easy Weight Loss Diet - Diet Pills - Best Diet Programs - Weight Loss Pills - Fitness - Lose Weight

 

Sex, drugs, violence and getting fat - Is this what the media's doing to our kids?

June 19, 7:05 PM

 

American kids spend six hours a day with media – internet, TV, videogames, etc. and their health is going down the tubes (no pun intended). A coincidence?

Sex, drugs, violence and getting fat - Is this what the media's doing to our kids?

[Nitack]

New Evidence That Vinegar May Be Natural Fat-fighter

 

New Evidence That Vinegar May Be Natural Fat-fighter

 

ScienceDaily (June 22, 2009) — Researchers in Japan are reporting new evidence that the ordinary vinegar — a staple in oil-and-vinegar salad dressings, pickles, and other foods — may live up to its age-old reputation in folk medicine as a health promoter. They are reporting new evidence that vinegar can help prevent accumulation of body fat and weight gain.

 

I'm trying to think of a way to work more vinegar into my diet and the only thing I could come up with is by eating more salad, which would explain any resulting weight loss on it's own. It would also diminish the coolness of this information as I am a firm believer that salad is what food eats.

[dannieyankee]

I do not mean to sound ignorant, but I believe (at least in the United States) this is bull.

 

I know I gained weight by not doing anything and eating more than I needed. I know in the United States, the culture is 'more food'. The idea is that you pay for quantity, not quality. I only wish I lived in a European country, where the idea was quality over quantity. I'd rather have really good food rather than lots of it.

 

This virus may exist, but it might just be a coincidence. Maybe fat people just are too lazy to wash their hands, thus more prone to disease.

 

BTW, I'm legally overweight, so I'm not just making fun of another group of people.

[Nitack]

I do not mean to sound ignorant, but I believe (at least in the United States) this is bull.

 

I know I gained weight by not doing anything and eating more than I needed. I know in the United States, the culture is 'more food'. The idea is that you pay for quantity, not quality. I only wish I lived in a European country, where the idea was quality over quantity. I'd rather have really good food rather than lots of it.

 

This virus may exist, but it might just be a coincidence. Maybe fat people just are too lazy to wash their hands, thus more prone to disease.

 

BTW, I'm legally overweight, so I'm not just making fun of another group of people.

 

Dannie,

 

Not all of us think that there is some voodoo cause for obesity. Some of us (like myself) do think that the root cause is not enough movement and too much food intake. I feel that all of the other stuff posted here like viruses, bacteria, processing food, etc, do have a real effect, but they only influence one side of the energy equation (energy in vs. energy out) and do not hold the ultimate answer. Others here feel that there must be some explanation beyond just the energy in vs. energy out theory. Be warned, some people here will call you "simplistic" for daring to state that you feel that this is a problem of lifestyle and there is not some underlying cause that can be scientifically investigated and solved. And for full disclosure, I too am well overweight and got that way through my own choices and maintaining an intake of food that exceeded my daily energy needs.

[dannieyankee]

Dannie,

 

Not all of us think that there is some voodoo cause for obesity. Some of us (like myself) do think that the root cause is not enough movement and too much food intake. I feel that all of the other stuff posted here like viruses, bacteria, processing food, etc, do have a real effect, but they only influence one side of the energy equation (energy in vs. energy out) and do not hold the ultimate answer. Others here feel that there must be some explanation beyond just the energy in vs. energy out theory. Be warned, some people here will call you "simplistic" for daring to state that you feel that this is a problem of lifestyle and there is not some underlying cause that can be scientifically investigated and solved. And for full disclosure, I too am well overweight and got that way through my own choices and maintaining an intake of food that exceeded my daily energy needs.

 

I sympathise with your idea that their is not ALWAYS a direct in v. out scenario; for example, certain birth controls can make women gain weight. Obviously it is no longer that simple scenario 100% - however, I believe that the large majority of people do not even realise how little energy they use. For instance, it is well known that doctors do not always believe their patients who say they 'Eat healthy and exercise but are still overweight'. People underestimate how much they eat and overesetimate how much they exercise, making them believe that there MUST not be a reason for them to be fat other than some disease or virus. I know people who tell me they always eat right and exercise - then turn around and eat a plateful of Cuban food (which, by the way, is EXTREMELY calorie-enriched) and sit in front of a computer all day. They exercise a lot because once a month they do some yardwork for 2-4 hours.

 

So, yes, they may call be simplistic and negative, but I prefer the more accurate term 'realistic'.

[HydrogenBond]

One of the problems that makes it harder to reduce the rate of obesity, is because science creates too many excuses. All these excuses are created by empirical science. Although empirical correlation may show useful trends in populations, it does not firmly point the finger to you, you or you. As such, if you are part of a population, you get to use the excuse even if there is no cause and effect for you as an individual.

 

For example, if one made a valid correlation that showed that purple people are more prone to obesity, and I am a purple person, and want to eat more, I can use this excuse and say it is in my ethnic makeup. I am covered by the umbrella. If I start to exercise and get bored I can say, why do I bother, I am purple and purple people have been shown to be bigger than other groups.

 

If a study could correlate auto exhaust and obesity, I could use that as an excuse to go to the big city for dining. The traffic is particularly bad today, which may explain why I crave two desserts. Empirical science organizes the data in ways where there is plenty of room under a bunch of umbrellas for people who don't belong in the world of cause and effect.

 

Let me give an example how the umbrella effect works. The family is planning a camping trip. Before we go, we will do a bunch of studies. One study states that particular date shows an increase incident of rain based on historical data over 100 years. A random sampling of camps sites shows there are an average of 0.1 ant hills on each site, which has doubled the risks from last year. If I don't want to go camping, but wish to stay home, I now have two good scientific excuses, which may not occur on that day on that site, when the family gets there. If we didn't have this umbrella, I would have no scientific excuse to stay home. It would look irrational.

[dannieyankee]

I quite agree, HydrogenBond. The main problem with people getting fat is that there is no one really pointing a finger at them and saying 'This is something you brought upon yourself, now do something about it'. All these excuses being generated makes it seem like it is less necessary to fix it, because it's not really your fault.

[Racoon]

One of the problems that makes it harder to reduce the rate of obesity, is because science creates too many excuses. All these excuses are created by empirical science. Although empirical correlation may show useful trends in populations, it does not firmly point the finger to you, you or you. As such, if you are part of a population, you get to use the excuse even if there is no cause and effect for you as an individual.

 

For example, if one made a valid correlation that showed that purple people are more prone to obesity, and I am a purple person, and want to eat more, I can use this excuse and say it is in my ethnic makeup. I am covered by the umbrella. If I start to exercise and get bored I can say, why do I bother, I am purple and purple people have been shown to be bigger than other groups.

 

If a study could correlate auto exhaust and obesity, I could use that as an excuse to go to the big city for dining. The traffic is particularly bad today, which may explain why I crave two desserts. Empirical science organizes the data in ways where there is plenty of room under a bunch of umbrellas for people who don't belong in the world of cause and effect.

 

Let me give an example how the umbrella effect works. The family is planning a camping trip. Before we go, we will do a bunch of studies. One study states that particular date shows an increase incident of rain based on historical data over 100 years. A random sampling of camps sites shows there are an average of 0.1 ant hills on each site, which has doubled the risks from last year. If I don't want to go camping, but wish to stay home, I now have two good scientific excuses, which may not occur on that day on that site, when the family gets there. If we didn't have this umbrella, I would have no scientific excuse to stay home. It would look irrational.

 

WTF are you trying to say??

 

You have not explained anything having to to do with obesity.

 

It is Very Simple People!

Burn more Calories than you Ingest!

 

I:rant:

[Nitack]

WTF are you trying to say??

 

You have not explained anything having to to do with obesity.

 

It is Very Simple People!

Burn more Calories than you Ingest!

 

I:rant:

 

He actually explained a very good point to this whole debate. This very thread is indicative of the problem. Science has provided us with a wealth of data that suggests that there are mitigating factors which can explain why some people burn less calories or might be prone to eat more than they need.

 

The problem is that people in general tend to rationalize in order to protect their fragile egos. Science has provided a way for obese people to rationalize out that it must not be their fault because they heard on the radio, or read a blurb in a newspaper that says that some people are prone to weight gain. Those people do not hear "prone" or even "more likely", all they hear is "causes weight gain" and rationalize out that they must be one of those people. They did not understand what was being said, nor did they even confirm that they are part of the affected group. But it is far easier to believe that you are a victim of a biological conspiracy to make you fat, than to own up to your own actions (or lack of) and admit that you made yourself fat through poor choices.

[Michaelangelica]

Interesting how ingrained the 'fat-people are lazy' prejudice is.

I am not saying that over-eating fatty foods and lack of exercise is NOT a problem especially in the States. Oz visitors/tourists there cannot believe the size of restaurant meals-- and we are big eaters.

There are other factors like soft drink in plastic bottles, drugs, hereditary, body's processing ability, epigenetics, that help explain obesity in countries where people are starving.

[Michaelangelica]

Q: In the online audio presentation, Dr. Dana Dolinoy states that the epigenome is responsible for determination of cell type and activity. Does the bisphenol A finding suggest that fetal or environmental exposure to plastics could play a direct role in a genetic propensity toward obesity in humans?

Chantel Smith, Toronto, Canada

 

Q: Could there be a connection between the increase in plastics in our environment and rising obesity rates?

Randy Grenier, Waltham, Massachusetts

 

A: We have recently demonstrated that exposure of pregnant mice to bisphenol A (BPA), a building block of polycarbonate plastics and epoxy resins used to make consumer items ranging from water bottles to dental sealants, significantly reduces DNA methylation in Avy mice (Dolinoy et al., Proc. Natl. Acad. Sci. USA 104: 13056-13061, 2007). This results in the birth of more yellow offspring, mice that become obese and have a higher incidence of diabetes and cancer as adults. Thus, there could be a connection between the increase in plastics in our environment and the rising incidence of obesity in humans. However, such an association will not be able to be demonstrated unequivocally until the expression and function of genes involved in human obesity are shown to be altered by BPA.

 

[Editor's note: For more on the agouti mice, see A Tale of Two Mice.]

Q: If BPA has the same effect on humans as it did the mice in your study, why aren't all human babies born sick and obese?

Anonymous

 

A: BPA exposure during pregnancy increases the incidence of yellow offspring, but it does not result in all of the offspring having a yellow coat color and becoming obese. Therefore, if BPA has the same effect on humans as it does in mice, it would simply increase the percentage of humans who become obese as the BPA exposure increases. This happens to be the situation found in Western cultures, regardless of whether BPA is the culprit.

 

Q: How do the exposure levels of BPA in the agouti mice experiments compare to human exposure levels—especially exposure levels in pregnant women?

Dr. Gloria Jahnke, Chapel Hill, North Carolina

 

A: It is difficult to compare the BPA dose used in our mouse study with that to which humans are exposed, because in humans, the BPA is found in the plasma or excreted in the urine. We can't tell exactly how much of the chemical people ingest. The level of BPA that the pregnant mice were exposed to in our study was five times lower than the maximum nontoxic threshold dose in rodents (Dolinoy et al., Proc. Natl. Acad. Sci. USA 104: 13056-13061, 2007). Although this is likely higher than typical human exposure, it produced no significant effects on reproductive outcomes, litter size, or offspring health at birth. It did, however, markedly increase the incidence of mice born with a yellow coat color—animals that become obese and have higher incidences of diabetes and cancer as adults.

NOVA | scienceNOW | Epigenetics: Ask the Expert | PBS