Wednesday, December 30, 2015

Does the Vitamin and Mineral Content of Food Influence Our Food Intake and Body Fatness?

The Claim: We Overeat Because Our Diet is Low in Vitamins and Minerals

We know that animals, including humans, seek certain properties of food.  Humans are naturally attracted to food that's high in fat, sugar, starch, and protein, and tend to be less enthusiastic about low-calorie foods that don't have these properties, like vegetables (1).  Think cookies vs. plain carrots.

In certain cases, the human body is able to detect a nutritional need and take steps to correct it.  For example, people who are placed on a calorie-restricted diet become hungry and are motivated to make up for the calorie shortfall (23).  People who are placed on a low-protein diet crave protein and eat more of it after the restriction is lifted (4).  Humans and many other animals also crave and seek salt, which supplies the essential minerals sodium and chlorine, although today most of us eat much more of it than we need to.  At certain times, we may crave something sweet or acidic, and pregnant women are well known to have specific food cravings and aversions, although explanations for this remain speculative.  Research suggests that certain animals have the ability to correct mineral deficiencies by selecting foods rich in the missing mineral (5).

These observations have led to a long-standing idea that the human body is able to detect vitamin and mineral (micronutrient) status and take steps to correct a deficit.  This has led to the secondary idea that nutrient-poor food leads to overeating, as the body attempts to make up for low nutrient density by eating more food.  In other words, we overeat because our food doesn't supply the micronutrients our bodies need, and eating a micronutrient-rich diet corrects this and allows us to eat less and lose body fat.  These ideas are very intuitive, but intuition doesn't always get you very far in biology.  Let's see how they hold up to scrutiny.

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Saturday, December 19, 2015

The Potato Diet

In 2010, I wrote a series of blog posts on the health properties of potatoes (1, 2, 3).  The evidence showed that potatoes are non-toxic, filling per calorie, remarkably nutritious, and can be eaten as almost the sole source of nutrition for extended periods of time (though I'm not recommending this).  Traditional South American cultures such as the Quechua and Aymara have eaten potatoes as the major source of calories for generations without any apparent ill effects (3).  This is particularly interesting since potatoes are one of the highest glycemic and most insulin-stimulating foods known.

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Monday, December 14, 2015

A Sign of the Times

Every now and then, I venture out to go shopping at mainstream chain clothing stores.  Although I find it onerous, there are certain things I can't get at thrift stores.  For example, I can never find nice jeans.

The last time I set foot in these stores was about two years ago.  It was tough to find pants my size at that time-- many stores simply didn't sell pants with a 30 inch waist.  This year, it was even harder, since some of the stores that formerly carried 30W pants no longer did.  I managed to find my usual 30W 30L size in two stores, but I had a bizarre experience in both cases.   I put them on, and they were falling off my waist.  Since my waist size hasn't changed in two years, and my old 30W 30L pants of the same brand still fit the same as they did when I bought them two years ago, I have to conclude that both stores have changed their definition of "30 inches".  My new size is 28W 30L, which is tough to find these days.
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Food Reward Friday

This week's "winner"...

The Pizza Hut hot dog stuffed crust pizza!

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Sunday, December 13, 2015

Is it Time to Re-write the Textbooks on Insulin and Obesity? Part II

A new paper published on December 6th in the journal Science once again tackles the question of whether elevated insulin drives the development of obesity (1).  Mice were generated that lack Jun kinases 1 and 2 specifically in immune cells, impairing their ability to produce inflammation while having very few off-target effects.  These mice do not become insulin resistant when placed on a fattening diet, and their insulin levels do not increase one iota.  Are they protected from obesity?  People who read the last post should know the answer already.
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Thursday, December 10, 2015

Does "Metabolically Healthy Obesity" Exist?

Obesity is strongly associated with metabolic alterations and negative health outcomes including diabetes, cardiovascular disease, and some types of cancer (1234).  Excess body fat is one of the primary causes of preventable health problems and mortality in the United States and many other affluent nations, ranking in importance with cigarette smoking and physical inactivity.  Obesity is thought to contribute to disease via the metabolic disturbances it causes, including excess glucose and lipids in the circulation, dysregulated hormone activity including insulin and leptin, and inflammatory effects.  This immediately raises two questions:
  1. Does metabolically healthy obesity exist?
  2. If so, are metabolically healthy obese people at an elevated risk of disease and death?

Does metabolically healthy obesity exist?

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Wednesday, December 9, 2015

60 Minutes Report on the Flavorist Industry

A reader sent me a link to a recent CBS documentary titled "Tweaking Tastes and Creating Cravings", reported by Morley Safer.

Safer describes the "flavorist" industry, entirely dedicated to crafting irresistible odors for the purpose of selling processed and restaurant food.  They focused on the company Givaudin.  Dr. David Kessler, author of The End of Overeating, makes an appearance near the end.

Here are a few notable quotes:

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Sunday, December 6, 2015

Is it Time to Re-write the Textbooks on Insulin and Obesity?

A recent study in Cell Metabolism by Dr. Arya Mehran and colleagues found a result that, according to a press release, "could overturn widely accepted notions about healthy eating habits" (1), and has set the Internet abuzz.

In this study, researchers generated mice that lack one copy of the pancreatic insulin gene, and compared them to mice carrying both copies (2).  Then, they exposed both groups to a fattening diet, and found that mice lacking one copy of the insulin gene secreted less insulin than the comparison group (i.e., they did not develop the same degree of hyperinsulinemia).  These mice were also completely resistant to fat gain, while the comparison group became obese.  The authors came to some rather large conclusions based on these results, suggesting that the "accepted model" that hyperinsulinemia is the result of obesity is "incompatible with our results that put the insulin hypersecretion genetically upstream of obesity".  Ergo, diet causes hyperinsulinemia, which causes fat gain.  It's a familiar argument to those who frequent Internet diet-health circles, except in this case the hyperinsulinemia is caused by a high-fat diet.

The problem is that the "accepted model" they want to replace overnight didn't come out of thin air-- it emerged from a large body of research, which was almost completely ignored by the authors.  When carefully considered, this evidence suggests an alternative explanation for the results of Dr. Mehran and colleagues.

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Wednesday, December 2, 2015

New Review Papers on Food Reward

As research on the role of reward/palatability in obesity continues to accelerate, interesting new papers are appearing weekly.  Here is a roundup of review papers I've encountered in the last three months.  These range from somewhat technical to very technical, but I think they should be mostly accessible to people with a background in the biological sciences. 

Food and Drug Reward: Overlapping Circuits in Human Obesity and Addiction
Written by Dr. Nora D. Volkow and colleagues.  This paper describes the similarities between the mechanisms of obesity and addiction, with a focus on human brain imaging studies.  Most researchers don't think obesity is an addiction per se, but the mechanisms (e.g., brain areas important for reward) do seem to overlap considerably.  This paper is well composed and got a lot of media attention.  Dr. Volkow is the director of the National Institute on Drug Abuse, a branch of the National Institutes of Health.  The NIH is the main source of biomedical research funding in the US, and also conducts its own research.

Here's a quote from the paper:

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