Obesity: A Big Fat Surprise

Pretty much everybody these days knows that we are in the grip of an Obesity epidemic and most people know the two major causes; that we eat too much and move too little. The Obesity epidemic is developing at a frightening rate of knots and, of equal concern, is accompanied by epidemics in Type II Diabetes (it is no longer appropriate to call it adult-onset diabetes due to the increasing incidence in children) and the more complex and life-threatening epidemic that not many people talk about, Metabolic Syndrome (see my other article on that).

1985

2005

The speed at which these epidemics are increasing is one of the greatest causes for concern. We hear about this in the news, but the slides below put it in real perspective; although these figures are from the US, the RATE OF INCREASE is similar in a lot of Western Nations.

There is much conjecture in the research papers and public domain about the cause or causes of the increased incidence of Obesity, and much of the blame is laid at the door of the big 2 –we eat too much and move too little. However, scientific attempts to prove that these two factors explain all of the increases in Obesity have come up a little short; a 2006 review paper by 20 experts in the International Journal of Obesity suggests there are other culprits. Let us now discuss some other contributors to the problem.

Darwin was wrong

Our ancestors used to experience a food pattern of periods of feast, followed by periods of famine – this resulted in the development of a thrifty genotype, which means that our bodies are extremely efficient in the storage & utilization of food. So in terms of genes, it was a case of survival of the fattest rather than survival of the fittest. This suggests that as a species, we have evolved to adapt to our environmental circumstances. However, genes take a while (1000’s of years in most cases) to react and it’s only in the last 40 or 50 years (and only in the western world) that we have had an abundance of available energy-dense food, coupled with sedentary lifestyles. Consider that at the turn of the 20th century, Australians walked an average of 20,000-22,000 steps per day; now an average office-worker walks between 3,000-5,000 steps per day.

The Stress Vortex

It’s no secret that our lifestyles are becoming increasingly stressful, and much of it is down to the workplace. It appears that the old stereotype of an Aussie bludger is well and truly dead – recent figures have revealed that Australians work more hours than any other industrialized nation, bar India and Argentina!

Our stress response was developed long ago to enable us to combat or flee imminent danger and was thus labeled the ‘Fight or Flight’ response. The stress hormones (mainly adrenalin and nor-adrenalin) very quickly increase heart rate, mobilize blood glucose, speed up breathing and divert blood from our digestive system to our working muscles. The physical exertion of fight or flight helps to dissipate the stress response and let the body return to its normal resting state.

However, most of today’s stressors do not require a physical response, so our body does not return to homeostasis as in the above case. In this instance, blood glucose and circulating hormones can stay elevated for many hours, which can lead to tissue degeneration over time. Additionally, when we are exposed to prolonged or very intense stress, another stress hormone kicks in – Cortisol. This is the main glucocorticoid in our body and it has a range of pretty nasty effects if it is elevated for prolonged periods. It negatively effects insulin sensitivity, frazzles our brain cells, slows down our metabolic rate (encouraging the body to store more fat) and relocates fat from other parts of the body to the abdominal area. Enough said?

Not Enough Sleep

If you ask people why we need to sleep, most will respond that it is necessary mainly for the brain. However, recent research seems to indicate that it plays a key role in the maintenance of weight as well.

Several large studies from around the world have linked sleep to obesity. The US nurses’ Health Study (which has been tracking 68000 women) found that the amount of sleep was inversely proportional to weight – those who slept 5 hours per night gained more weight.

During the study than those who slept 6 hours, who in turn gained more weight than those who slept 7 hours.
Although this evidence is largely circumstantial, there is more direct evidence to back it up. Endocrinologists have discovered that the hormones responsible for hunger and satiety are directly influenced by the amount of sleep we get. Ghrelin (the hormone that makes us hungry) levels rise significantly with sleep deprivation, while levels of the satiety hormone, Leptin, fall. Cortisol, the major long-term stress hormne, also rises the day after a poor night’s sleep. Researchers at the University of Brussels concluded that these hormonal changes ‘could lead to excessive calorie intake when food is freely available’, such as in our society.

This information is interesting when viewed in the light of sleeping trends over the last 50 years; we slept an average of 8.5 hours in the 1960’s and the national average in both Australia and the US is now less than 7 hours.

Climate Control

It would appear that indoor heating has a role to play in the current obesity epidemic. Unlike reptiles, which depend on the external environment to control their body temperature, we warm-blooded humans have the ability to thermo-regulate, or maintain our core body temperature by sweating or shivering and both of these acts serve to burn up energy. For humans, a thermoneutral environment (where we neither need to sweat or shiver) is 27 degrees for the naked body.
Heating and air-conditioning may influence obesity in different ways. Studies performed in enclosed chambers (where energy expenditure can be measured very accurately) have shown that reducing the temperature from 27 degrees to 22 degrees results in an extra 239 calories being burned per day. When you consider that temperatures in the average British home have risen from 13 degrees in 1970 to 18 degrees in the year 2000, it’s obvious that there has been a significant energy saving (which translates into weight gain).

Air-conditioning works the other way around. David Allison, a biostatistician from the University of Alabama, points out that there’s good evidence to show that high temperatures reduce the amount that people eat. When you consider the astronomical rise in the amount of homes with air-conditioning, it’s reasonable to assume that as a nation we are probably eating more than we did when air-conditioning was solely for the rich.

Prescription Junkies

It is very clear that as a nation, we take more prescription drugs than we ever have. Whilst there is no doubt that most of these drugs are beneficial in combating the symptoms or conditions from which an individual suffers, it is equally clear that almost all prescription drugs have side effects and many relate to weight gain.

Beta blockers tend to add around 1.2kg to the average user, whilst taking the contraceptive pill for 2 years comes with the burden of 5kg extra. Even worse than that re a class of used drugs to treat psychosis, known as neuropletics, which weigh in with an average weight gain of 4kg in the first 10 weeks and another 4-5kg in the year that follows.

The list doesn’t stop there; drugs that treat Epilepsy, HIV and Diabetes all pack on the kilos and even over-the-counter antihistamines can expand the waistline.

Fat by pollution

You’d pretty much have to live in Outer Mongolia to be oblivious to the impact that pollution has on global warming, but pollution also appears to have an effect on our waistlines. Unless you are a true ‘greenie’, you’re probably exposed to an incredible volume of chemicals in daily life, such as flavourings, plastics, perfumes, resins, solvents and other industrial chemicals. We now know that some of these chemicals disrupt the levels of certain hormones such as oestrogen and this appears to be one of the major problems; when estrogen does not function properly, we tend to put on weight. Armed with this knowledge, it’s clear you’d have to be an industrial lobbyist to deny there was a problem.

Although direct observation of these effects is almost impossible to gauge, pretty good evidence is emerging from animal studies. Mice that have been exposed to small amounts of the pesticide dieldrin almost double their body fat, whilst rats that have traces of hexachlorobenzene gain more weight than their counterparts not exposed to the pesticide, despite eating only half as much food.

We also have some human studies to back this up. Studies on humans who have been exposed to PCBs by eating fish from America’s Great Lakes put on weight in a dose-response fashion – the more PCBs they were exposed to, the more weight they gained.

Your Prenatal Environment

Your chances of being a hefty adult (and possibly your risk of developing some diseases) may be determined in part before you were born. It is very well established that children of obese mothers are much more likely to become obese themselves. Whilst some of this can be explained by genes and by children mimicking the eating behaviours of their parents, there may also be a contribution that is labeled ‘intrauterine programming’.

Studies conducted on mice have shown that offspring of a mother fed a high-fat diet during pregnancy were much more likely to become fat than the offspring of mothers fed a normal diet. This effect even persisted when the grandmother’s (but not the mother’s) diet was manipulated, suggesting that the effect can last for 2 or 3 generations.

On the other hand, under-nutrition probably has the same effect. In what is known as Barker’s hypothesis, it appears that energy restriction in the womb may lead to obesity in later life. This theory developed from studies of the famine imposed on the Netherlands by the Nazis during WWII. Due to meticulous record keeping by the Dutch, these people were able to be tracked down after the war and the researchers took other factors such as economic status into account. The study clearly showed that the children of mothers that suffered from energy restriction and malnutrition through the famine had a much greater predisposition for Obesity, along with a number of chronic diseases.

Vitamin D deficiency

Recent research has shown that not only are Australians now similar to Scots and Scandanavians in terms of vitamin D deficiency, but that a lack of Vitamin D is strongly associated with excess weight and impairments in brain function. The take-home message – get 20-30 minutes of unprotected sun per day to help weight control and brain health.