Sunday, June 28, 2015

Food Reward: a Dominant Factor in Obesity, Part VII

Now that I've explained the importance of food reward to obesity, and you're tired of reading about it, it's time to share my ideas on how to prevent and perhaps reverse fat gain.  First, I want to point out that although food reward is important, it's not the only factor.  Heritable factors (genetics and epigenetics), developmental factors (uterine environment, childhood diet), lifestyle factors (exercise, sleep, stress) and dietary factors besides reward also play a role.  That's why I called this series "a dominant factor in obesity", rather than "the dominant factor in obesity".
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New Study: Is a Calorie a Calorie?

A new study in JAMA led by Dr. Cara B. Ebbeling and colleagues purports to challenge the idea that all calories are equally fattening (1).  Let's have a look.  When thinking about the role of calorie intake in body fatness, there are basically three camps:

1.    Calories don’t matter at all, only diet composition matters.
2.    Calories are the only thing that matters, and diet composition is irrelevant.
3.    Calories matter, but diet composition may also play a role.

The first one is an odd position that is not very well populated.  The second one has a lot of adherents in the research world, and there’s enough evidence to make a good case for it.  It’s represented by the phrase ‘a calorie is a calorie’, i.e. all calories are equally fattening.  #1 and #2 are both extreme positions, and as such they get a lot of attention.  But the third group, although less vocal, may be closest to the truth. 
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Food Reward Friday

This week's lucky "winner"... beer!!



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Thursday, June 25, 2015

What Puts Fat Into Fat Cells, and What Takes it Out?

Body fatness at its most basic level is determined by the rate of fat going into vs. out of fat cells. This in/out cycle occurs regardless of conditions outside the cell, but the balance between in and out is influenced by a variety of external factors.  One of the arguments that has been made in the popular media about obesity goes something like this:  


A number of factors can promote the release of fat from fat cells, including:
Epinephrine, norepinephrine, adrenocorticotropic hormone (ACTH), glucagon, thyroid-stimulating hormone, melanocyte-stimulating hormone, vasopressin, and growth hormone
 But only two promote fat storage:
Insulin, and acylation-stimulating protein (ASP)*
Therefore if we want to understand body fat accumulation, we should focus on the latter category, because that's what puts fat inside fat cells.  Simple, right?

Can you spot the logical error in this argument?

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Wednesday, June 24, 2015

The Genetics of Obesity, Part I

Choosing the Right Parents: the Best Way to Stay Lean?

In 1990, Dr. Claude Bouchard and colleagues published a simple but fascinating study demonstrating the importance of genetics in body fatness (1).  They took advantage of one of the most useful tools in human genetics: identical twins.  This is what happens when a single fertilized egg generates two embryos in utero and two genetically identical humans are born from the same womb.   By comparing identical twins to other people who are not genetically identical (e.g., non-identical twins), we can quantify the impact of genes vs. environment on individual characteristics (2).

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Tuesday, June 23, 2015

Drug Cessation and Weight Gain

Commenter "mem", who has been practicing healthcare for 30+ years, made an interesting remark that I think is relevant to this discussion:
Recovering substance dependent people often put on lots of weight and it is not uncommon for them to become obese or morbidly obese.
This relates to the question that commenter "Gunther Gatherer" and I have been pondering in the comments: can stimulating reward pathways through non-food stimuli influence body fatness?  

It's clear that smoking cigarettes, taking cocaine and certain other pleasure drugs suppress appetite and can prevent weight gain.  These drugs all activate dopamine-dependent reward centers, which is why they're addictive.  Cocaine in particular directly inhibits dopamine clearance from the synapse (neuron-neuron junction), increasing its availability for signaling.
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Sunday, June 21, 2015

Food Reward Friday

This week's lucky "winner"... low-carb gluten-free bacon chocolate mocha ice cream cake!!


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Friday, June 19, 2015

A Pressure Cooker for the 21st Century

Pressure cookers are an extremely useful kitchen tool.  They greatly speed cooking and reduce energy usage by up to 70 percent.  This is because as pressure increases, so does the boiling point of water, which is the factor that limits cooking speed in water-containing foods (most foods).  If it weren't for my pressure cooker, I'd rarely eat beets or globe artichokes.  Instead of baking, boiling or steaming these for 60-90 minutes, I can have them soft as butter in 30.  But let's face it: most people are intimidated by pressure cookers.  They fear the sounds, the hot steam, and the perceived risk of explosion.  I escaped this because I grew up around them.

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Thursday, June 18, 2015

Food Reward: a Dominant Factor in Obesity, Part VI

Reward Centers can Modify the Body Fat Setpoint

Dopamine is a neurotransmitter (chemical that signals between neurons) that is a central mediator of reward and motivation in the brain.  It has been known for decades that dopamine injections into the brain suppress food intake, and that this is due primarily to its action in the hypothalamus, which is the main region that regulates body fatness (1).  Dopamine-producing neurons from reward centers contact neurons in the hypothalamus that regulate body fatness (2).  I recently came across a paper by a researcher named Dr. Hanno Pijl, from Leiden University in the Netherlands (3).  The paper is a nice overview of the evidence linking dopamine signaling with body fatness via its effects on the hypothalamus, and I recommend it to any scientists out there who want to read more about the concept.
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Saturday, June 13, 2015

New Study Demonstrates that Sugar has to be Palatable to be Fattening in Mice

Dr. Anthony Sclafani's research group just published a study definitively demonstrating that high palatability, or pleasantness of taste, is required for sugar to be fattening in mice (1).  Dr. John Glendinning was lead author. Dr. Sclafani's group has done a lot of excellent research over the years.  Among other things, he's the person who invented the most fattening rodent diet in the world-- the 'cafeteria diet'-- composed of human junk food. 

Mice and rats love sweet food and drinks, just like humans.  If you give them a choice between plain water and sugar water, they'll overconsume the sugar water and become obese.  I have argued, based on a large body of evidence, that the reward value and palatability* of these solutions are important to this process (2, 3, 4).  This is really just common sense honestly, because by definition if the solution weren't rewarding the mice wouldn't go out of their way to drink it instead of water, the same way people wouldn't go out of their way to get soda if it weren't rewarding.  But it's always best to confirm common sense with research.
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Tuesday, June 9, 2015

Sugar Intake and Body Fatness in Non-industrial Cultures

Around the world, non-industrial cultures following an ancestral diet and lifestyle tend to be lean. When they transition a modern diet and lifestyle, they typically put on body fat and develop the classic "diseases of civilization" such as diabetes and cardiovascular disease.  If we can understand the reasons why this health transition occurs, we will understand why these problems afflict us today.  Research has already identified a number of important factors, but today I'm going to discuss one in particular that has received a lot of attention lately: sugar.

There's an idea currently circulating that sugar is the main reason why healthy traditional cultures end up obese and sick.  It’s easy to find non-industrial cultures that are lean and don’t eat much sugar, and it’s easy to find industrial cultures that are obese and eat a lot of it.  But many factors are changing simultaneously there.  We could use the same examples to demonstrate that blue jeans and hair gel cause obesity.  If sugar is truly the important factor, then cultures with a high sugar intake, but an otherwise ancestral diet and lifestyle, should also be overweight and sick.  Let’s see if that's true. 

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Sunday, June 7, 2015

Food Reward Friday

This week's "winner" will certainly be the most controversial yet... bacon!!
Bacon is a fatty cut of pork (typically side or back) that has been thinly sliced, cured, then cooked until crispy.  This results in a fatty, salty, savory flavor that almost everyone loves.  Bacon's extremely high calorie density, saltiness, and savory flavor give it a reward value that competes with chocolate and ice cream.  Sometimes it's even used to flavor chocolate and ice cream!

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Saturday, June 6, 2015

Update

I haven't been putting much effort into blogging these past few weeks.  Frankly, a little break has been nice while I take care of other things in my life.  But I haven't been twiddling my thumbs.  Obesity research hasn't slowed down and there are many topics that I'd love to write about here if I had the time.  I'll be starting a new series soon on the genetics of obesity-- a fascinating subject.  I also plan to cover some of my recent publications on obesity and blood glucose control by the brain.  Last but not least, we will soon roll out a substantially upgraded version of the Ideal Weight Program.  Those who have already purchased the program will continue to have access to the new version.


Friday, June 5, 2015

Calories Still Matter

The Centers for Disease Control's NHANES surveys documented a massive increase in obesity in the United States between the 1960-62 and 2007-2008 survey periods (1).  In 1960, 13 percent of US adults were obese, while in 2008 that number had risen to 34 percent.  The prevalence of extreme obesity increased from 0.9 to 6.0 percent over the same time period!

Something has changed, but what?  Well, the most parsimonious explanation is that we're simply eating more.  Here is a graph I created of our calorie intake (green) overlaid on a graph of obesity prevalence (blue) between 1970 and 2008:

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Tuesday, June 2, 2015

Food Reward: a Dominant Factor in Obesity, Part V

Non-industrial diets from a food reward perspective

In 21st century affluent nations, we have unprecedented control over what food crosses our lips.  We can buy nearly any fruit or vegetable in any season, and a massive processed food industry has sprung up to satisfy (or manufacture) our every craving.  Most people can afford exotic spices and herbs from around the world-- consider that only a hundred years ago, black pepper was a luxury item.  But our degree of control goes even deeper: over the last century, kitchen technology such as electric/gas stoves, refrigerators, microwaves and a variety of other now-indispensable devices have changed the way we prepare food at home (Megan J. Elias.  Food in the United States, 1890-1945). 

To help calibrate our thinking about the role of food reward (and food palatability) in human evolutionary history, I offer a few brief descriptions of contemporary hunter-gatherer and non-industrial agriculturalist diets.  What did they eat, and how did they prepare it? 
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