Tag Archives: overweight

Do Sugar Substitutes Cause Overweight and T2 Diabetes?

We don’t know with certainty yet. But a recent study suggests that non-caloric artificial sweeteners do indeed cause overweight and type 2 diabetes in at least some folks. The study at hand is very small, so I wouldn’t bet the farm on it. I’m not changing any of my recommendations at this point.

exercise for weight loss and management, dumbbells

Too many diet sodas?

 

The proposed mechanism for adverse metabolic effects of sugar substitutes is that they alter the mix of germs that live in our intestines. That alteration in turn causes  the overweight and obesity. See MedPageToday for the complicated details. The first part of the article is about mice; humans are at the end.

Some quotes:

“Our results from short- and long-term human non-caloric sweetener consumer cohorts suggest that human individuals feature a personalized response to non-caloric sweeteners, possibly stemming from differences in their microbiota composition and function,” the researchers wrote.

The researchers further suggested that these individualized nutritional responses may be driven by personalized functional differences in the micro biome [intestinal germs or bacteria].

***

Diabetes researcher Robert Rizza, MD, of the Mayo Clinic in Rochester, Minn., who was not involved with the research, called the findings “fascinating.”

He noted that earlier research suggests people who eat large amounts of artificial sweeteners have higher incidences of obesity and diabetes. The new research, he said, suggests there may be a causal link.

“This was a very thorough and carefully done study, and I think the message to people who use artificial sweeteners is they need to use them in moderation,” he said. “Drinking 17 diet sodas a day is probably a bad idea, but one or two may be OK.”

I won’t argue with that last sentence! (Unless you have phenylketonuria and want to use aspartame.)

Finally, be aware that several clinical studies show no linkage between human consumption of non-caloric artificial sweeteners and overweight, obesity, and T2 diabetes.

Steve Parker, M.D.

How Did the Agricultural and Industrial Revolutions Change Human Diets?

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With the advent of the Agricultural Revolution 10,000 years ago, mankind took a giant leap away from two million years of evolutionary adaptation. The Industrial Revolution that started in the late 18th century—about 240 years ago—was yet another watershed event. The Agricultural Revolution marks the end of the Old Stone Age and the start of the Neolithic period. The Neolithic ended four to six thousand years ago, replaced by the Bronze Age (or Iron Age in some areas).

EFFECTS OF THE AGRICULTURAL REVOLUTION

The Agricultural Revolution refers to farming the land on a large scale, and all that entails: gathering and planting seeds, nurturing the soil, breeding plants for desirable traits, storing crops, processing plants to maximize digestibility, domesticating wild animals and enhancing them by selective breeding, setting down roots in one geographic location, etc. The revolution allowed for the expansion of reliable food supplies and an explosion of human populations. Less time was needed for hunting and foraging, allowing for the development of advanced cultures.

It wasn’t all sunshine and roses, however. We have evidence that human health deteriorated as a result of the revolution. For instance, some populations declined in height and dental health.

EFFECTS OF THE INDUSTRIAL REVOLUTION

The Industrial Revolution starting in the late 18th century brought its own changes to our diet. Progressive industrialization and affluence changed the composition of our “energy foods.” For instance, peasants in poor developing countries derive about 75% of their calories from high-fiber starchy foods. With modernization, fiber-free fats and sugars become the source of 60% of calories. U.S. consumption of cereal fiber decreased by 90% between 1880 and 1976. In addition to lower fiber content, refined wheat products also had fewer vitamins and other micronutrients. Machinery allowed the production of margarine and vegetable oils. Sugar imports and snacking increased in the Western world.

Obesity suddenly became very common in the upper classes of Europe and England toward the end of the 17th century and even more so in the 18th. Weights also increased throughout populations of developed countries. For instance, if we look at U.S. men of average height between the ages of 30 to 34, average weights were 148 lb (66 kg) in 1863, but were up to 170 lb (77 kg) in 1963. Our current obesity epidemic didn’t even start until around 1970.

Let’s look at a few major U.S. diet changes from 1860 to 1975. Energy derived from protein rose from 12% to 14–15%. Energy from fat rose from 25 to 42% of calories. Energy from starches fell from 53 to 22%. Calories from sugar rose from 10 to 24%. Total carbohydrate calories fell from 63 to 46%.

It only takes a few decades to see major changes in a population’s food consumption. For instance, U.S. per capita consumption of salad and cooking oils increased from 21.2 pounds per person in 1980 to 54.3 pounds per person in 2008 (USDA data). I refer to these oils as industrial seed oils, and they include soybean, corn, and sunflower oil. We’re not entirely sure what effect these have on health. Some suspect they are related to obesity, heart disease, and other “diseases of civilization.” Per capita soybean oil consumption in the U.S. increased over a thousand-fold between 1909 and 1999, to 7.4% of total calories. It’s in many of our processed foods. Linoleic acid is a predominant omega-6 fatty acid in seed oils. Linoleic acid consumption increased by 200% in the last century. Thanks to increasing omega-6 fatty acid consumption, the omega-6/omega-3 ratio increased from 5.4:1 to 9.6:1 between 1909 and 2009. (Reference: Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. “Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century.” Am J Clin Nutr. 2011 May;93(5):950-62. doi: 10.3945/ajcn.110.006643. Epub 2011 Mar 2.)

The Industrial Revolution also introduced into our diets large amounts of man-made trans-fats, which are highly detrimental to cardiovascular health. Public outcry has lead to diminishing amounts of dietary trans-fats over the last decade.

An occasional teaspoon of sugar probably won't hurt you

Added sugars: table sugar in coffee, high-fructose corn syrup in ketchup

At his Whole Health Source blog, Dr. Stephan Guyenet and Jeremy Landen produced a graph of U.S. sugar consumption from 1822 to 2005. Dr. Guyenet wrote, “It’s a remarkably straight line, increasing steadily from 6.3 pounds (2.9 kg) per person per year in 1822 to a maximum of 107.7 pounds (49 kg) per person per year in 1999. Wrap your brain around this: in 1822, we ate the amount of added sugar in one 12 ounce can of soda (360 ml) every five days, while today we eat that much sugar every seven hours.” Note that added sugars overwhelmingly supply only one nutrient: pure carbohydrate without vitamins, minerals, antioxidants, protein, fat, etc.

 

Think about the typical Western or Standard American Diet (SAD) eaten by an adult these days. It provides an average of 2673 calories a day (not accounting for wastage of calories in restaurants; 2250 cals/day is probably a more accurate figure for actual consumption). Added sugars provide 459 of those calories, or 17% of the total. Grains provide 625 calories, or 23% of the total. Most of those sugars and grains are in processed, commercial foods. So added sugars and grains provide 40% of the total calories in the SAD. That’s a huge change from the diet of our prehistoric ancestors. Remember, we need good insulin action to process these carbohydrates, which is a problem for diabetics. Anyone going from the SAD to pure paleo eating will be drastically reducing intake of added sugars and grains, our current major sources of carbohydrate. They’ll be replacing them with foods that generally require less insulin for processing. (Figures are from an April 5, 2011, infographic at Civil Eats: http://www.civileats.com.)

FUN FACTS! (from the U.S. Dept. of Agriculture)

  • A typical carbonated soda contains the equivalent of 10 tsp (50 ml) of table sugar.
  • The typical U.S. adult eats 30 tsp (150 ml) daily of added sweeteners and sugars.
  • U.S total grain product consumption was at record lows in the 1970s, at 138 pounds per person. By 2008, grain consumption was up by 45%, to 200 pounds per person.
  • Total caloric sweetener consumption (by dry weight) was 110 pounds per person in the 1950s. By 2000, it was up 39% to 150 pounds.
  • Between 1970 and 2003, consumption of added fats and oils rose by 63%, from 53 to 85 pounds. (How tasty would that be without starches and sugars? Not very.)
  • In 2008, “added fat” calories in the U.S. adult diet were 641 (24% of total calories).

Steve Parker, M.D.

Americans Eat Too Much

The U.S. adult population in the 1970s ate an average of 2400 calories a day. By the 2000s, our calories were up to 2900.

Putting a face on the statistics

Putting a face on the statistics

What did average adult weight do as we increased daily calories by 500? It increased by 8.6 kg, from 72.2 to 80.6 kg. In U.S. units, that’s a 19 lb gain, from 159 to 178 lb.

Children increased their average intake by 350 cals/day over the same time frame.

If I recall correctly, I’ve seen other research suggesting the daily calorie consumption increase has been more like 150 to 350 per day (lower end for women, higher for men). I suspect these latter figures are more accurate.

Details are in the American Journal of Clinical Nutrition.

The study authors don’t say for sure why we’re eating more, but offhand mention an “obesogenic food environment.”  They don’t think decreased physical activity is the cause of our weight gain; we’re fatter because we eat too much.

Steve Parker, M.D.

h/t Ivor Goodbody

Pollution May Be Causing T2 Diabetes and Obesity

It sounds like Jerome Ruzzin is convinced that’s the case. I put some thought into it last August and was skeptical—still am, but I’m keeping an open mind. Mr. Ruzzin has a review article published in 2012 at BMC Public Health (“Public health concern behind the exposure to persistent organic pollutants and the risk of metabolic diseases”). Here’s his summary:

The global prevalence of metabolic diseases like obesity and type 2 diabetes, and its colossal economic and social costs represent a major public health issue for our societies. There is now solid evidence demonstrating the contribution of POPs [persistent organic pollutants], at environmental levels, to metabolic disorders. Thus, human exposure to POPs might have, for decades, been sufficient and enough to participate to the epidemics of obesity and type 2 diabetes. Based on recent studies, the fundaments of current risk assessment of POPs, like “concept of additive effects” or “dioxins and dl-PCBs induced similar biological effects through AhR”, appear unlikely to predict the risk of metabolic diseases. Furthermore, POP regulation in food products should be harmonized and re-evaluated to better protect consumers. Neglecting the novel and emerging knowledge about the link between POPs and metabolic diseases will have significant health impacts for the general population and the next generations.

Read the whole enchilada.

The cold-water fatty fish I so often recommend to my patients could be hurting them. They are major reservoirs of food-based POPs.

Steve Parker, M.D.

Is Dining Out Making Us Fat?

So easy to over-eat!

So easy to over-eat!

The U.S. trend of increasing overweight and obesity started about 1970. I wonder if eating away from home is related to the trend. I found a USDA report with pertinent data from 1977 to 1995. It also has interesting info on snacking and total calories consumed. Some quotes:

“We define home and away-from-home foods based on where the foods are obtained, not where they are eaten. Food at home consists of foods purchased at a retail store, such as a grocery store, a convenience store, or a supermarket. Food away from home consists of foods obtained at various places other than retail stores (mainly food-service establishments).”

***

“Over the past two decades, the number of meals consumed has remained fairly stable at 2.6 to 2.7 per day. However, snacking has increased, from less than once a day in 1987-88 to 1.6 times per day in 1995. The increased popularity in dining out is evident as the proportion of meals away from home increased from 16 percent in 1977-78 to 29 percent in 1995, and the proportion of snacks away from home rose from 17 percent in 1977-78 to 22 percent in 1995. Overall, eating occasions (meals and snacks) away from home increased by more than two-thirds over the past two decades, from 16 percent of all eating occasions in 1977-78 to 27 percent in 1995.”

***

“Average caloric intake declined from 1,876 calories per person per day in 1977-78 to 1,807 calories per person per day in 1987-88, then rose steadily to 2,043 calories per person per day in 1995.”

***

“These numbers suggest that, when eating out, people either eat more or eat higher-calorie foods or both.”

Parker here. I’m well aware that these data points don’t prove that increased eating-out, increased snacking,  and increased total calorie consumption have caused our overweight and obesity problem. But they sure make you wonder, don’t they? None of these factors was on a recent list of potential causes of obesity.

If accurate, the increased calories alone could be the cause. Fast-food and other restaurants do all they possibly can to satisfy your cravings and earn your repeat business.

If you struggle with overweight, why not cut down on snacking and eating meals away from home?

Steve Parker, M.D.

Update:

Here’s a pie chart I found with more current and detailed information from the U.S. government (h/t Yoni Freedhoff):

feb13_feature_guthrie_fig03

Does Dining Out Cause Obesity?

Home-cooked meal

Home-cooked meal

The U.S. trend of increasing overweight and obesity started about 1970. I wonder if eating away from home is related to the trend. I found a USDA report with pertinent data from 1977 to 1995. It also has interesting info on snacking and total calories consumed. Some quotes:

“We define home and away-from-home foods based on where the foods are obtained, not where they are eaten. Food at home consists of foods purchased at a retail store, such as a grocery store, a convenience store, or a supermarket. Food away from home consists of foods obtained at various places other than retail stores (mainly food-service establishments).”

***

“Over the past two decades, the number of meals consumed has remained fairly stable at 2.6 to 2.7 per day. However, snacking has increased, from less than once a day in 1987-88 to 1.6 times per day in 1995. The increased popularity in dining out is evident as the proportion of meals away from home increased from 16 percent in 1977-78 to 29 percent in 1995, and the proportion of snacks away from home rose from 17 percent in 1977-78 to 22 percent in 1995. Overall, eating occasions (meals and snacks) away from home increased by more than two-thirds over the past two decades, from 16 percent of all eating occasions in 1977-78 to 27 percent in 1995.”

***

“Average caloric intake declined from 1,876 calories per person per day in 1977-78 to 1,807 calories per person per day in 1987-88, then rose steadily to 2,043 calories per person per day in 1995.”

***

“These numbers suggest that, when eating out, people either eat more or eat higher-calorie foods or both.”

Parker here. I’m well aware that these data points don’t prove that increased eating-out, increased snacking,  and increased total calorie consumption have caused our overweight and obesity problem. But they sure make you wonder, don’t they? None of these factors was on a recent list of potential causes of obesity.

If accurate, the increased calories alone could be the cause. Fast-food and other restaurants do all they possibly can to satisfy your cravings and earn your repeat business.

If you struggle with overweight, why not cut down on snacking and eating meals away from home?

Steve Parker, M.D.

Heresy! Sleep Deprivation NOT Linked to Adult Obesity

Paleobetic diet

I bet she’s faking

It’s currently popular to blame inadequate sleep time for overweight and obesity. I found a study supporting that idea in children, but not adults. Here’s the authors’ conclusion:

While shorter sleep duration consistently predicts subsequent weight gain in children, the relationship is not clear in adults. We discuss possible limitations of the current studies: 1.) the diminishing association between short sleep duration on weight gain over time after transition to short sleep, 2.) lack of inclusion of appropriate confounding, mediating, and moderating variables (i.e. sleep complaints and sedentary behavior), and 3.) measurement issues.

I found another analysis from a different team that is skeptical about the association of sleep deprivation and obesity in adults.

Everybody knows adults are getting less sleep now than we did decades ago, right? Well, not really. From Sleep Duration Across the Lifespan: Implications for Health:

Twelve studies, representing data from 15 countries and a time period of approximately 40 years, attempted to document changes in sleep duration over that time period. They found that, overall, there is no consistent evidence that sleep durations worldwide are declining among adults. Sleep duration decreased in six countries, sleep duration increased in seven countries, and mixed results were detected in two (one of which was the USA). In particular, the data from the USA suggest that although mean sleep duration may have actually increased slightly over the past 40 years, the proportion of short sleepers (six hours per night or less) also seems to have increased over the past several decades.

See, it’s complicated. Don’t believe everything you read. Not even this.

Steve Parker, M.D.

PS: It’s fun being an iconoclast now and then!

Do Environmental Contaminants Cause Type 2 Diabetes or Obesity?

"Today we're going to learn about odds ratios and relative risk."

“Today we’re going to learn about odds ratios and relative risk.”

A month ago I watched part of a documentary called “Plastic Planet” on Current TV (Now Al Jazeera TV). It was alarming. Apparently chemicals are leaking out of plastics into the environment (or into foods contained by plastic), making us diabetic, fat, impairing our fertility, and God knows what else. The narrator talked like it was a sure thing. I had to go to work before it was over. A couple chemicals I remember being mentioned are bisphenol A (BPA) and phthalates. I sorta freaked my wife out when I mentioned it to her. I always take my lunch to work in plastic containers and often cover microwaved food with Glad Press’n Seal plastic wrap.

A few days later I saw a report of sperm counts being half of what they were just half a century ago. (It’s debatable.) Environmental contaminants were mentioned as a potential cause.

So I spent a couple hours trying to figure out if chemical contamination really is causing obesity and type 2 diabetes. In the U.S., childhood obesity has tripled since 1980, to a current rate of 17%. Even preschool obesity (age 2-5) doubled from 5 to 10% over that span. In industrial societies, even our pets, lab animals (rodents and primates), and feral rats are getting fatter! The ongoing epidemics of obesity and type 2 diabetes, and our lack of progress in preventing and reversing them, testify that we may not have them figured out and should keep looking at root causes to see if we’re missing anything.

Straightaway, I’ll tell you it’s not easy looking into this issue. The experts are divided. The studies are often contradictory or inconsistent. One way to determine the cause of a condition or illness is to apply Bradford Hill criteria (see bottom of page for those). We could reach a conclusion faster if we did controlled exposure experiments on humans, but we don’t. We look at epidemiological studies and animal studies that don’t necessarily apply to humans.

Regarding type 1 diabetes and chemical contamination, we have very little data. I’ll not mention type 1 again.

What Does the Science Tell Us?

For this post I read a couple pertinent scientific reviews published in 2012, not restricting myself to plastics as a source of chemical contaminants.

The first was REVIEW OF THE SCIENCE LINKING CHEMICAL EXPOSURES TO THE HUMAN RISK OF OBESITY AND DIABETES from non-profit CHEM Trust, written by a couple M.D., Ph.D.s. I’ll share some quotes and my comments. My clarifying comments within a quote are in [brackets].

“It should be noted that diabetes itself has not been caused in animals exposed to these chemicals [a long list] in laboratory studies, but metabolic disruption closely related to the pathogenesis of Type 2 diabetes has been reported for many chemicals.”

“In 2002, Paula Baillie-Hamilton proposed a hypothesis linking exposure to chemicals with obesity, and this is now gaining credence. Exposure to low concentrations of some chemicals leads to weight gain in adult animals, while exposure to high concentrations causes weight loss.”

“The obesogen hypothesis essentially proposes that exposure to chemicals foreign to the body disrupts adipogenesis [fat tissue growth] and the homeostasis and metabolism of lipids (i.e., their normal regulation), ultimately resulting in obesity. Obesogens can be functionally defined as chemicals that alter homeostatic metabolic set-points, disrupt appetite controls, perturb lipid homeostasis to promote adipocyte hypertrophy [fat cells swelling with fat], stimulate adipogenic pathways that enhance adipocyte hyperplasia [increased numbers of fat cells] or otherwise alter adipocyte differentiation during development. These proposed pathways include inappropriate modulation of nuclear receptor function; therefore, the chemicals can be termed EDCs [endocrine disrupting chemicals].”

Don't assume mouse physiology is the same as human's

Don’t assume mouse physiology is the same as human’s

Literature like this talks about POPs: persistent organic pollutants, sometimes called organohalides. The POPs and other chemical contaminants that are currently suspicious for causing obesity and type 2 diabetes include arsenic, pesticides, phthalates, metals (e.g., cadmium, mercury, organotins), brominated flame retardants, DDE (dichloro-diphenyldichloroethylene), PCBs (polychlorinated biphenyls), trans-nonachlor, dioxins.

Another term you’ll see in this literature is EDCs: endocrine disrupting chemicals. These chemicals mess with hormonal pathways. EDCs that mimic estrogen are linked to obesity and related metabolic dysfunction. Some of the chemicals in the list above are EDCs.

The fear—and some evidence—is that contaminants, whether or not EDCs, are particularly harmful to embryos, fetuses, and infants. For instance, it’s pretty well established that mothers who smoked while pregnant predispose their offspring to obesity in adulthood. (Epigenetics, anyone?) Furthermore, at the right time in the life cycle, it may only take small amounts of contaminants to alter gene expression for the remainder of life. For instance, the number of fat cells we have is mostly determined some time in childhood (or earlier?). As we get fat, those cells simply swell with fat. When we lose weight, those cells shrink, but the total cell number is unchanged. What if contaminant exposure in childhood increases fat cell number irrevocably? Does that predispose to obesity later in life?

The authors note that chemical contaminants are more strongly linked to diabetes than obesity. They do a lot of hemming and hawing, using “maybe,” “might,” “could,” etc. They don’t have a lot of firm conclusions other than “Hey, people, we better wake up and look into this further, and based on the precautionary principle, we better cut back on environmental chemical contamination stat!” [Not a direct quote.] It’s clear they are very concerned about chemical contaminants as a public health issue.

Here’s the second article I read: Role of Environmental Chemicals in Diabetes and Obesity: A National Toxicology Program Workshop Review. About 50 experts were empaneled. Some quotes and my comments:

“Overall, the review of the existing literature identified linkages between several of the environmental exposures and type 2 diabetes. There was also support for the “developmental obesogen” hypothesis, which suggests that chemical exposures may increase the risk of obesity by altering the differentiation of adipocytes [maturation and development of fat cells] or the development of neural circuits that regulate feeding behavior. The effects may be most apparent when the developmental [early life] exposure is combined with consumption of a high-calorie, high-carbohydrate, or high-fat diet later in life.”

“The strongest conclusion from the workshop was that nicotine likely acts as a developmental obesogen in humans. This conclusion was based on the very consistent pattern of overweight/obesity observed in epidemiology studies of children of mothers who smoked during pregnancy (Figure 1) and was supported by findings from laboratory animals exposed to nicotine during prenatal [before birth] development.”

I found some data that don’t support that conclusion, however. Here’s a graph of U.S. smoking rates over the years since 1944. Note that the smoking rate has fallen by almost half since 1983, while obesity rates, including those of children, are going the opposite direction. If in utero cigarette smoke exposure were a major cause of U.S. childhood obesity, we’d be seeing less, not more, childhood obesity. I suppose we could still see a fall-off in adult obesity rates over the next 20 years, reflecting lower smoking rates.  But I doubt that will happen.

The CDC suggests a slight drop in childhood obesity in recent years (2010 data).

“The group concluded that there is evidence for a positive association of diabetes with certain organochlorine POPs [persistent organic pollutants]. Initial data mining indicated the strongest associations of diabetes with trans-nonachlor, DDT (dichloro-diphenyltrichloroethane)/DDE (dichloro-diphenyldichloroethylene)/DDD (dichloro-chlorophenylethane), and dioxins/dioxin-like chemicals, including polychlorinated biphenyl (PCBs). In no case was the body of data considered sufficient to establish causality [emphasis added].”

“Overall, this breakout group concluded that the existing data, primarily based on animal and in vitro studies [no live animals involved], are suggestive of an effect of BPA on glucose homeostasis, insulin release, cellular signaling in pancreatic β cells, and adipogenesis. The existing human data on BPA and diabetes (Lang et al. 2008Melzer et al. 2010) available at the time of the workshop were considered too limited to draw meaningful conclusions. Similarly, data were insufficient to evaluate BPA as a potential risk factor for childhood obesity.”

“It was not possible to reach clear conclusions about BPA and obesity from the existing animal data. Although several studies report body weight gain after developmental exposure, the overall pattern across studies is inconsistent.”

“The pesticide breakout group concluded the epidemiological, animal, and mechanistic data support the biological plausibility that exposure to multiple classes of pesticides may affect risk factors for diabetes and obesity, although many significant data gaps remain.”

“Recently, the focus of investigations has shifted toward studies designed to understand the consequences of developmental exposure to lower doses of organophosphates [insecticides], and the long-term effects of these exposures on metabolic dysfunction, diabetes, and obesity later in life. [All or nearly all the studies cited here were rodent studies, not human.] The general findings are that early-life exposure to otherwise subtoxic levels of organophosphates results in pre-diabetes, abnormalities of lipid metabolism, and promotion of obesity in response to increased dietary fat.”

In case it’s not obvious, remember that “association is not the same as causation.” For example, in the Northern hemisphere, higher swimsuit purchases are associated with summer. Swimsuit sales and summer are linked (associated), but one doesn’t cause the other. Swimsuit purchases are caused by the desire to go swimming, and that’s linked to warm weather.

In at least one of these two review articles, I looked carefully at the odds ratios of various chemicals linked to adverse outcomes. One way this is done is too measure the blood or tissue levels of a contaminant in a population, then compare the adverse outcome rates in animals with the highest and lowest levels of contamination. For instance, if those with the highest contamination have twice the incidence of diabetes as the least contaminated, the odds ratio is 2. You could also call it the relative risk. Many of the potentially harmful chemicals we’re considering have a relative risk ratio of 1.5 to 3. Contrast those numbers with the relative risk of death from lung cancer in smokers versus nonsmokers: the relative risk is 10. Smokers are 10 times more likely to die of lung cancer. That’s a much stronger association and a main reason we decided smoking causes lung cancer. Odds ratios under two are not very strong evidence when considering causality; we’d like to have more pieces of the puzzle.

These guys flat-out said arsenic is not a cause of diabetes in the U.S.

Overall, the authors of the second article I read were clearly less alarmed than those of the first. Could the less-alarmed panelists have been paid off by the chemical industry to produce a less scary report, so as not to jeopardize their profits? I don’t have the resources to investigate that possibility. The workshop was organized (and paid for, I assume) by the U.S. government, but that’s no guarantee of pure motivation by any means.

You need a break. Enjoy.

You need a break. Enjoy.

My Conclusions

For sure, if I were a momma rat contemplating pregnancy, I’d avoid all those chemicals like the plague!

It’s premature to say that these chemical contaminants are significant causes of obesity and type 2 diabetes in humans. That’s certainly possible, however. We’ll have to depend on unbiased scientists to do more definitive research for answers, which certainly seems a worthwhile endeavor. Something tells me the chemical producers won’t be paying for it. Universities or governments will have to do it.

You should keep your eyes and ears open for new evidence.

There’s more evidence for chemical contaminants as a potential cause of type 2 diabetes than for obesity. Fetal and childhood exposure may be more harmful than later in life.

If I were 89-years-old, I wouldn’t worry about these chemicals causing obesity or diabetes. For those quite a bit younger, taking action to avoid these environmental contaminants is optional. As for me, I’m drinking less water out of plastic bottles and more tap water out of glass or metal containers. Yet I’m not sure which water has fewer contaminants.

Humans, particularly those anticipating pregnancy and child-rearing, might be well advised to minimize exposure to the aforementioned chemicals. For now, I’ll leave you to your own devices to figure out how to do that. Good luck.

Why not read the two review articles I did and form your own opinion?

Unless the chemical industry is involved in fraud, bribery, obfuscation, or other malfeasance, the Plastic Planet documentary gets ahead of the science. I’m less afraid of my plastic containers now.

Steve Parker, M.D.

Additional Resources:

Sarah Howard at Diabetes and the Environment (focus on type 1 but much on type 2 also).

Jenny Ruhl, who thinks chemical contaminants are a significant cause of type 2 diabetes (search her site).

From Wikipedia:

The Bradford Hill criteria, otherwise known as Hill’s criteria for causation, are a group of minimal conditions necessary to provide adequate evidence of a causal relationship between an incidence and a consequence, established by the English epidemiologist Sir Austin Bradford Hill (1897–1991) in 1965.

The list of the criteria is as follows:

  1. Strength: A small association does not mean that there is not a causal effect, though the larger the association, the more likely that it is causal.
  2. Consistency: Consistent findings observed by different persons in different places with different samples strengthens the likelihood of an effect.
  3. Specificity: Causation is likely if a very specific population at a specific site and disease with no other likely explanation. The more specific an association between a factor and an effect is, the bigger the probability of a causal relationship.
  4. Temporality: The effect has to occur after the cause (and if there is an expected delay between the cause and expected effect, then the effect must occur after that delay).
  5. Biological gradient: Greater exposure should generally lead to greater incidence of the effect. However, in some cases, the mere presence of the factor can trigger the effect. In other cases, an inverse proportion is observed: greater exposure leads to lower incidence.
  6. Plausibility: A plausible mechanism between cause and effect is helpful (but Hill noted that knowledge of the mechanism is limited by current knowledge).
  7. Coherence: Coherence between epidemiological and laboratory findings increases the likelihood of an effect. However, Hill noted that “… lack of such [laboratory] evidence cannot nullify the epidemiological effect on associations”.
  8. Experiment: “Occasionally it is possible to appeal to experimental evidence”.
  9. Analogy: The effect of similar factors may be considered.

Science-Based Medicine blog has more on Hill’s criteria.

Do Warm Houses and Workplaces Contribute to Obesity?

Dr. Stephan Guyenet thinks they might. It’s not so much heat as it is failing to expose our bodies adequately to temperatures around 60° F (15.6° C) or lower on a regular basis. Here’s a human experiment Dr. G wrote about:

The second study went further, using a longer cold exposure protocol to investigate changes in fat mass among people with low brown fat activity at baseline (4).  Researchers exposed volunteers to 63 F (17 C) air for two hours a day over a six-week period; again I assume they were lightly clothed.  As in the previous study, they observed an increase in brown fat activity with cold training, and they found that calorie expenditure was higher when subjects were in the ‘cold’ air.  After six weeks of training, body fat mass had declined by about 5 percent.  This is despite the fact that all subjects were lean to begin with!

Read the rest.

I thought this study tied in with that one showing an inverse relationship between altitude and obesity. Environmental temperature rises roughly 3° F with every 1,000 feet (305 meters). But the altitude study controlled for (accounted for) temperature, meaning that the temperature had nothing to do with the association.

Somebody’s probably already tried to link environmental temperatures—whether inside the house or out—to obesity rates. Let me know if you find it.

—Steve

PS: A few minutes at Pubmed.gov revealed this 2013 abstract:

Objective: Raised ambient temperatures may result in a negative energy balance characterized by decreased food intake and raised energy expenditure. This study tested whether indoor temperatures above the thermoneutral zone for clothed humans (approx. 23 o C) were associated with a reduced body mass index (BMI). Design and Methods: Participants were 100,152 adults (≥ 16 years) drawn from 13 consecutive annual waves of the nationally representative Health Survey for England (1995 – 2007). Results: BMI levels of those residing in air temperatures above 23 o C were lower than those living in an ambient temperature of under 19 o C (b = -.233, SE =.053, p <.001), in analyses that adjusted for participant age, gender, social class, health and the month/year of assessment. Robustness tests showed that high indoor temperatures were associated with reduced BMI levels in winter and non-winter months and early (1995 – 2000) and later (2001 – 2007) survey waves. Including additional demographic, environmental, and health behavior variables did not diminish the link between high indoor temperatures and reduced BMI. Conclusions: Elevated ambient indoor temperatures are associated with low BMI levels. Further research is needed to establish the potential causal nature of this relationship.

PPS: And there’s this abstract, probably from the altitude study I mentioned:

http://www.ncbi.nlm.nih.gov/pubmed/23357956

“There was an approximately parabolic relationship between mean annual temperature and obesity, with maximum prevalence in counties with average temperatures near 18 °C [64.4° F].”

I don’t have the full article, but parabolic, to me in this context, probably means the obesity incidence was highest at 64.4° F, with lower obesity incidence both above and below 64.4°.

Of course, living in a particular environment doesn’t equate to exposing yourself to outdoor temperatures. But it makes sense that someone living in a cold environment will have more cold exposure than someone in a hot climate.

Perhaps 64.4° F is a sweet spot for efficient body temp regulation and energy partitioning. Living at temps significantly above or below that may cost you energy-wise: you expend extra calories maintaining a normal body temperature, tending to result in lower obesity incidence.

Do High Insulin Levels Cause Memory Loss and Dementia?

dementia, memory loss, Mediterranean diet, low-carb diet, glycemic index, dementia memory loss

Don’t wait to take action until it’s too late

Insulin resistance and high blood insulin levels promote age-related degeneration of the brain, leading to memory loss and dementia according to Robert Krikorian, Ph.D. He’s a professor in the Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati Academic Health Center.  He has an article in a recent issue of Current Psychiatry – Online.

Proper insulin signaling in the brain is important for healthy functioning of our brains’ memory centers.  This signaling breaks down in the setting of insulin resistance and the associated high insulin levels.  Dr. Krikorian makes much of the fact that high insulin levels and insulin resistance are closely tied to obesity.  He writes that:

Waist circumference of ≥100 cm (39 inches) is a sensitive, specific, and independent predictor of hyperinsulinemia for men and women and a stronger predictor than body mass index, waist-to-hip ratio, and other measures of body fat.

Take-Home Points

Dr. Krikorian thinks that dietary approaches to the prevention of dementia are effective yet underutilized.  He mentions reduction of insulin levels by restricting calories or a ketogenic diet: they’ve been linked with improved memory in middle-aged and older adults. His theory is also consistent with the commonly seen association of type 2 diabetes with dementia: overweight and obese type 2’s quite often have high insulin levels, at least in the early years.

Dr. K suggests the following measures to prevent dementia and memory loss:

  • eliminate high-glycemic foods like processed carbohydrates and sweets
  • replace high-glycemic foods with fruits and vegetables (the higher polyphenol intake may help by itself)
  • certain polyphenols, such as those found in berries, may be particularly helpful in improving brain metabolic function
  • keep your waist size under 39 inches (99 cm), or aim for that if you’re higher and overweight

Nearly all popular versions of the paleo diet would qualify as being low glycemic index.

I must mention that many dementia experts, probably most, are not as confident  as Dr. Krikorian that these dietary changes are effective.  I think they are, to a degree.

The Mediterranean diet is high in fruits and vegetables and relatively low-glycemic.  It’s usually mentioned by experts as the diet that may prevent dementia and slow its progression.

Read the full article.

I’ve written before about how blood sugars in the upper normal range are linked to brain degeneration.  Dr. Krikorian’s recommendations would tend to keep blood sugar levels in the lower end of the normal range.

Steve Parker, M.D.

PS: Speaking of dementia and ketogenic, have you ever heard of the Ketogenic Mediterranean Diet?  (Free condensed version here.)