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Apr 21
Film poster for An Inconvenient Truth
Image via Wikipedia

Thankfully the current generation of young people are far more aware of the environmental issues and willing to do something about it. They have taught their parents to recycle, use reusable grocery bags, to buy carbon credits (though controversial), etc, etc.  However, this same young generation is the fattest in our history (and potentially the least fit).

Does being overweight really coincide with the principles of trying to keep the planet healthy?

I have wanted to write a piece about this issue for awhile but didn’t have a nice published journal arguing what I thought were various obvious points, but now one has come out.

In a study published in the International Journal of Epidemiology by Edward and Roberts (2009) argues that food production is one of the main contributors (20%) to greenhouse gas emissions (H/T to esciencenews). If you have a population of people in the developed nations that are overweight (ranging from 20-65+ % of the population) this would have a number of implications. It costs more to transport the heavier people but also they are eating more than someone of normal weight and hence use up a greater amount of the valuable and dwindling energy resources and a greater amount of food producing land. This is not exactly rocket science to realize this.

Being overweight is equivalent to deciding to drive around in a SUV (or any other gas guzzler).

If people slimmed down (via escience news):

Transport-related emissions will also be lower because it takes less energy to transport slim people. The researchers estimate that a lean population of 1 billion people would emit 1.0 GT (1,000 million tonnes) less carbon dioxide equivalents per year compared with a fat one.

Really the comparison here was between a population of ‘lean’ with a mean body mass index (BMI) of 24.5 vs a more typical ‘developed’ country with a BMI of 29 (to give you a frame of reference normal weight is 18.5 -24.9, overweight is 25-29.9m and obese is 30+). The heavier population would consume 19% more food than the lean population.

I really don’t have to give you a bunch of numbers and facts I think all of you intuitively know that it only make sense that an overweight population consumes more energy and contributes a greater amount to environmental issues (including global warming).

I think the authors give a pretty clear statement in their discussion (GHG = global green house gases):

We argue that increased population adiposity, because of its contribution to climate change from additional food and transport GHG emissions, should be recognized as an environmental problem.

So if you care about the environment, be it you are young or old, then do your part and stay (or become) slim (meaning normal weight) - which will also contribute to your own health.

If you care about the planet’s health, then do something about it by taking care of your own health - by maintaining a healthy weight. Something for all of us to think about, but maybe this message has the best chance in taking hold in the current young generation who as a whole do care about the planet’s health.

Are you a gaz guzzler, a hybrid, an all electric, or even a highly efficient bicycle?

Apr 20

Is it not just the most humans see the glass as half full but most organisms?

Due to the few posts I have done recently on optimists (optimism is good for your health, is the glass half full or half empty: optimism and rACC activation) I couldn’t pass up the following story that was sent my way by a friend.

Eternal Optimist:

Science magazine mentions a new study comparing C elegans in good conditions or unfavorable environmental conditions (no food). This is how they described it:

The nematode appears to behave like an optimist: When conditions are favorable, it responds rapidly, but when conditions become unfavorable, the worm is slower to respond. During starvation, larvae are developmentally arrested and RNA polymerase II accumulates on the promoters of growth and development genes. This accumulation anticipates recovery from developmental arrest when these genes are rapidly up-regulated in response to feeding.

What they are saying is the at least C. elegans assume things are going to be good in the future (optimists) - they have hope - and hence they don’t respond quickly to starvation at a gene response level. Why should they alter their gene response because things are of course going to get better (or at least this is what they are betting on). On the other hand the organism is very quick to change its gene response to good conditions - food. Soon as they get access to food they act like things will never get tough again - time of plenty.

The paper they are referring to was recently published in Science by Baugh et al., 2009.

The expression profile of larvae fed for 12 hours and then starved for 3 hours
resembled larvae fed for 15 hours rather than those starved for 3 hours. Conversely, the expression profile of larvae starved for 12 hours and then fed for 3 hours did not resemble larvae starved for 15 hours but rather larvae fed for 3 hours.

(side note: if negative food supply continues long enough some organisms go into a preventive/survival mode in which reproduction is shut down and energy use is dramatically reduced)

The bigger question is do other organism show this same optimistic tendency, do humans? Previous research indicates the as a whole humans are quite optimistic (Schacter and Addis, Nature Neuroscience, 2007).

Most of us tend to be optimistic, which is a good thing because optimism is
associated with many benefits to both physical and mental health; optimists tend to be well adjusted psychologically and are equipped to handle stress well.

Okay, it appears that humans are a fairly optimistic species, which is very similar to the C. elegans (see also is the glass half full or half empty: optimism and rACC activation). However, there could be cost to pay from being overly optimistic:

If you are overly optimistic about the future then maybe you would not take appropriate safety measures (such as in our ancient ancestor’s time having a cache of food, or in our current world money saved up). One could argue a large contributor to our current financial crisis is the vast majority of individuals in the developed world were too optimistic about the future (they drank – overdosed on - the koolaid). They wore the rose tinted (or should I say the green tinted) glasses that colored their view of the world, of the future and they did not see the reality of the situation. Hence, took on overly optimistic debt load (personal level) or overly leveraged their position (banking/financial sector).

And could all of the over optimism be somewhat related to how much food you consume, or how much calorie supply you have stored in your body? The feeding and fasting response of C. elegans seems to be an ancient evolutionary ‘built’ in optimism at the genetic level. What happens if you live in a time of over abundance of food? Do you become overly optimistic and not able to respond to changing environmental and economic conditions? Is there a fundamental link between food and money?

From my piece on why a fed brain might influence economic choice, in which I quote Briers et al., 2006 (Hungry for money: the desire for caloric resources increases the desire for financial resources and vice versa).

Money is viewed as a means to obtain biologically relevant incentives (food), and food is viewed as a means of preventing the body’s energy resources from falling below an energy set point… Finally, the symmetric association between food and money may help explain why poor people are especially vulnerable to overeating and have ill health as a result. In industrialized countries such as the United States (Drewnowski & Specter, 2004), as well as in developing countries (James, 2004), obesity is usually associated with poverty. Perhaps in present-day societies, the attraction to money is so powerful that people who, relatively speaking, fail in their quest for (more) money become frustrated. Accordingly, as financial and caloric resources are exchangeable, they might tend to appease their desire for money by consuming more calories than is healthy.

The optimistic program might be great in the normal environment with plenty of feast and famine - and the only measurement of species success is at least producing new offspring that might benefit when better conditions return. But what happens in the time of ‘un-normal’ abundance? What happens when more than 50% of the population become overweight or obese? You might want to read about the possible link between the rise of obesity and the rise of debt.

However, if this built in genetic optimism survived untold millions of years of selection there is probably a pretty good reason. This built in optimistic genetic program must work under most conditions for various organisms. But I wonder if other creatures like the squirrel which in the summer and fall are storing away for the winter - do they have a different program?

I don’t know the answers but at least this gives us plenty of food for thought. The economics, and the neuroeconomics of food, money and optimism.

- thanks again to my friend for tipping me off to this article.

(see also: the neuroscience of hope)

Apr 15

Is the likelihood of you currently having or developing depression related to your body mass index?

Body mass index (BMI) is simply a comparison of a person’s body weight and height. Formerly, it is your weight in kg divided by the square of your height (kg/m2). You can go here to find out what your BMI is, using either imperial or metric measurements.

A BMI of under 18.5 is considered underweight, 18.5 - 25 is normal, above 25 to 30 is overweight, and over 30 is obese. With this knowledge what BMI do you think would be correlated with longest lifespan? And how much is lifespan reduced if you are overweight or obese?

Which of these groups do you think are more likely to develop depression? Before you guess you might want to refer back to my U shape curve blog piece.

Zhao et al., 2009 looked at data from 177,047 participants 18 years or older (American citizens) in which they were able to obtain self reported height and weight, along with current level of depression (diagnostic questionnaire) and life time self report. Take a look at their main figure.

a) is current depression, b) lifetime depression, c) anxiety.

As you can see there is a U shape curve, with those having a BMI of less than 18.5 and females with a BMI above 25 prone to depression. For males an increase in depression is not really noticeable until you get to the very high end of the BMI scale (35+). For females the lowest level of depression is for the BMI 18.5-25 group (normal weight). For males the range appears larger: 18.5 - 35. In c) the bottom graph we can see roughly the same story for anxiety. So it appears you can be too thin, but also too heavy.

I could show you more graphs of relative risks after taking into account confounding variables, but I think you get the idea. Even after adjusting for various confounding variable the authors conclude:

After adjusting for demographics, ORCs, lifestyle or psychosocial factors, compared with men with a normal BMI, men with a BMI >40 kg/m2 were significantly more likely to have current depression or lifetime diagnosed depression and anxiety; men with a BMI <18.5 kg/m2 were also significantly more likely to have lifetime diagnosed depression. Women who were either overweight or obese were significantly more likely than women with a normal BMI to have all the three psychiatric disorders.

The only thing that is surprising to me in the authors conclusion is that they don’t find females who are underweight (BMI < 18.5) also have higher levels of depression.

Other than showing you what body size/shape is correlated with increased depression, I wanted you to observe an example of the U shape curve in biology. I will be providing more of these in the future.

Take home message: As in many things, too much or too little might not be the best. Either end of the extreme in body mass index is correlated with higher levels of depression. For women there appears to be a narrower range of BMI that is correlated with lower level of depression as compared to men (this could be partially cultural).

Mar 19
Summer Fountain shows Obesety in Children as s...
Image by hyperscholar via Flickr

Yesterday, I told you that children who are overweight perform worse than their normal weighted counterparts on certain cognitive tasks related to planning. This piece was a follow-up to all the very similar results in adults.

With parents always wanting the best for their children then obviously they would be on the watch for obvious to the eyes bodily changes in their children.

But us humans don’t always see reality (or we tend to put on the rose tinted glasses). A series of research paper have found that parents do not judge their children weight/chubbiness correctly. Akerman et al., 2007 observed that when parents estimated weight and had normal weighted children they roughly equally underestimated (43.1%) or overestimated (49.3%) the child’s weight (with 7.6% being accurate). But things changed with the kids were either underweight or overweight. For the underweight children 70% of these parents overestimated the children’s weight (16% accurate, and 14% underestimated). For the overweight children 61.6% underestimated, 7.9% were accurate and 30.5 overestimated.

In another study the researchers found that not only did parents underestimate children measured weight but so did the children and their physicians (Chaimovitz et al., 2008). The conclusion of this paper was:

Many children underestimated their degree of
overweight. Their parents and even their attending physicians
shared this misperception. This study demonstrates the need to
further educate physicians to recognize obesity and overweight
so that they can counsel children and their families.

I find this very interesting because how are you going to fix a problem if you can’t see it staring you in the face. Parents and apparently doctors need to take off the rose tinted glasses and face reality. I wonder if the doctors (and parents) version of ‘normal’ has changed over the years because the average weight of children have increased over these years. The overweight silhouette is the new average ?

This is not only an American phenomena, as a Canadian study found very similar results with 63% of the parents with overweight children judging them as in the normal weight category (He and Evans, 2007). The title of this study was interesting: ‘Are parents aware their children are overweight or obese? Do they care?’

If you have a child maybe you want to accurately measure your child’s height and weight - and compare it to what is normal for the appropriate age range (see here). Your inability to see the reality of your child’s weight could lead to your child’s reduced cognitive ability. For if you don’t recognize the problem you can not fix it. And we naturally want the best for our kids - but then we have to view the situation correctly. While you are at it you might want to check you own body mass index (BMI) and calculate your number. Are you wearing rose tinted glasses?

caveat: BMI is not the be all measurement of appropriate body size - and can be innacurate in terms of ‘fatness’ so you might want to look into getting a proper body fat measurement (there are several options, from cheap and ‘reasonably’ accurate, to more expensive and subsequently more accurate).

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