Dr. Sharma's Obesity Notes

Have you ever wondered why it is almost impossible to only eat one potatoe chip or French fry?

Regular readers may recall a previous post on the discovery that we have specific oral sensory receptors that allow us to sense the ‘fattiness’ of food - a function that makes a lot of sense, given that dietary fat provides the densest source of caloric intake.

Now, Nicholas DiPatrizio and colleagues from the University of California, Irvine, have discovered that these oral dietary fat sensors activate a powerful ‘addiction-type’ mechanism in your gut that serves to promote further fat intake - their study is published in a recent issue of the Proceedings of the US National Academy of Science.

For their studies, the researchers used a well established ’sham feeding’ model in the rat, where liquid diets eaten by the animal can be drained from the stomach via a chronically implanted gastric cannula, thereby preventing them from reaching the small intestines.

Using this model, the researchers showed that ’sham feeding’ of a high-fat diet resulted in the potent activation of endocannabinoids in the early part of the small intestine by altering enzymatic activities that control endocannabinoid metabolism. The endocannbinoids (cannabis-like compounds produced in the body) are well known to play an important role in regulating ‘rewarding’ feeding behaviours.

This effect was abolished by surgical transection of the vagus nerve showing that the stimulation of these changes in the gut is driven through a centrally mediated neuronal pathway.

Furthermore, the local application of cannabinoid type 1 receptors blockers (e.g. rimonabant) in the small gut, reduced increased sham fat ingestion.

In other words, this study shows that oral sensing of fat sends a signal to the brain, which in turn sends a signal to the gut leading to formation of endocannabinoids, which in turn re-enforce fat eating.

This is probably why, just eating one piece of fatty food (say one potatoe chip or French fry) is so hard - simply eating one makes you want to continue eating till the whole bag or plate is empty.

Unfortunately, the drug rimonabant, used to effectively block this effect in this study, is no longer available for obesity management (it was withdrawn due to its negative impact on mood), but it may well be that other CB-1 inhibitors that do not enter the brain may prove to be effective to reduce fat intake.

Or, in the words of the authors:

“Our findings identify the gut endocannabinoid system as a critical component of the positive feedback mechanism that drives fat intake and suggest that therapeutic strategies aimed at restraining small intestinal endocannabinoid activity might help to selectively reduce the overeating of fatty foods.”

In the meantime using strategies based on limiting portion size, e.g. asking for a small serving of fries or transferring a small portion of chips into a separate bowl, while leaving the full bag in the pantry, may be the best strategy to thwart this mechanism.

AMS
Duchesnay, Quebec

Dipatrizio NV, Astarita G, Schwartz G, Li X, & Piomelli D (2011). Endocannabinoid signal in the gut controls dietary fat intake. Proceedings of the National Academy of Sciences of the United States of America PMID: 21730161

I always get nervous when anyone proclaims that the cause or solution to the obesity epidemic is any one factor.

As regular readers will appreciate, obesity is complex, heterogeneous and diverse. There are 100s of factors that can promote weight gain or make weight loss difficult and different factors are more or less important in different individuals - no diet, no exercise program, no psychological counseling, no medication, no surgery will ever be found that works for everyone.

That said, there may well be some factors that are more important than others, when it comes to issues like population exposure - even factors that have small individual effects, can have large population effects, simply because they affect so many people.

This does not mean that such factors are the most important or even the most powerful drivers of obesity in a given individual - in fact, in a given individual, this same factor may play absolutely no role - either because this individual is not exposed to this risk factor or because this person is genetically or biologically ‘resistant’ to this factor.

One of the factors that often comes up in obesity discussions is the role of fructose. While, I doubt that fructose (or any one factor) can explain all of the obesity problem (or provide a simple solution), there is some fascinating science about how fructose could possibly play a role.

This complex science (epidemiology, history, biochemistry, policies, politics, etc.) of fructose is comprehensively discussed in this fascinating and captivating 90 minute(!) presentation by Robert Lustig, Professor of Pediatrics in the Division of Endocrinology at the University of California, San Francisco.

Amazingly, this very scientific and rather lengthy video went ‘viral’ on YouTube and has been viewed almost 1.5 million times since it was originally posted back in 2009.

So grab a non-fructose-sweetened beverage, head to my blog page, and sit back as Lustig takes you through a lot of very interesting science (some of this may be too complex for some readers, but you’ll still get the picture).

By no means, am I as convinced as Lustig about fructose being the root of all ‘evil’, but this video certainly is highly educational and, if nothing else, reminds us of how complex human biology actually is.

AMS
Edmonton, Alberta

Despite all advances in gender equality, mothers overwhelmingly remain responsible for putting food on the family table.

Thus, any attempt at changing eating behaviours requires a sound understanding of the factors that determine mothers’ food choices for their families.

This issue is the topic of a study by Joyce Slater and colleagues from the University of Manitoba, published in Health Promotion International.

The researchers used qualitative methodology based on grounded theory to better understand the phenomena of food choice and food provisioning among employed middle-income mothers from Winnipeg.

All participants were born in Canada, were Caucasian, worked at least half-time at paid employment, lived with a male spouse working full-time, had at least one child between ages 5 and 12, had some post-secondary education and self-identified as having the primary responsibility for acquiring and preparing food for her family.

The methods consisted of extensive interviews and use of food choice maps to explore a wide range of determinants of food practices and choices.

Perhaps not surprisingly, the number one constraint that limited the preparation of healthy home cooked meals was lack of time!

As one participant put it:

“Life is far too rushed! Especially if you’re only getting home [from work] at, like anything after five is just a disaster. If you’re not home before quarter to five it’s like, you’re not going to make it! ‘Cause there’s evening events that are going to start and it’s like, oh man, now it’s the rush and a panic.”

The two main reasons for lack of time were employment and kids activities.

“All the women in this study described their family lives as being extremely busy due to their employment and children being engaged in multiple extracurricular events, which were felt to be important for their development. This contracted their food preparation time, however, resulting in the frequent use of convenience foods or take-away from restaurants, which also led to feelings of stress.”

The second major determinant of food choices were ‘picky eaters’:

“My daughter’s very picky, so who knows what she’ll eat what nights … it’s usually just a Pizza Pop or leftovers of a quick bowl of soup. We try to get her to eat what we eat, but it’s challenging. You don’t want it to be a battleground.”

While breakfast and lunch were rarely eaten together, most mothers appreciated the importance of having the family assembled for dinner - however, this also rarely happened due to busy and conflicting schedules.

Although mothers collectively perceived food as an important determinant of health,

“Many of the foods children preferred were perceived to be unhealthy by the mothers, but were frequently purchased because they knew they would be eaten, or it was believed that the children should have their way at least some of the time.”

Reasons for not eating enough fruits and vegetables boiled down to:

“…children not liking vegetables; they took too much time and work to prepare; it was not worth making them only for themselves and the women did not want to risk spending time making vegetables if they were going to be wasted.”

Although mothers appreciated that fathers may have a role to play - they preferred to make these choices themselves:

“Sometimes I wish he would help a bit more, but I still think I’m better off with the majority of it. Because, I said, I don’t think he would make as good of choices. He would give the kids Pizza Pops for lunch every day, and … vegetables?! Who cares? What do you need vegetables for!?”

“[Help with] groceries? No (laughter), not very often! I mean, you know, if I’m really really strapped he will go out but that’s not that often. He really doesn’t like grocery shopping.”

All of these findings have significant implications for improving population health:

“By purchasing and serving convenience foods over vegetables and healthier meals that take more preparation time, the women reinforce structural food norms within the family and within the retail grocery landscape that provides these foods for purchase. “

“Shifting norms surrounding the efforts put into food preparation are mutually reinforced by the women’s values, beliefs and identities, permitting the frequent use of these foods, thereby saving time. This is compounded by working outside the home and a busy family life, which leave considerably less time for preparing healthy foods and eating together. “

As the authors point out, educating mothers (or fathers) about healthy eating, although important, is insufficient to really change behaviour.

“Public health policy-makers should expand nutrition education initiatives to include … a more balanced discussion of domestic food work rather than perpetuating the current discourse on child obesity calling for greater ‘parental’ (maternal) responsibility. This could also include providing more flexibility for employees (male and female) to work part-time.

In addition, strategies to promote the uptake of more family food responsibility by male partners and children should be explored and promoted. A step towards this could be achieved through a re-introduction of school-based nutrition and food skills, not through traditional ‘home ec’ curriculum with gender-specific stereotypes, but teaching basic principles to feed young men and women, and their future families, within the current food environment.”

As I’ve discussed before, when trying to understand behaviours, it is far more important to explore the ‘why’ than the ‘what’.

This study certainly reminds us that for many, the key barrier to healthy eating is not lack of information on nutrients and food groups but rather having far too few minutes in your day.

Remember, the real problem with fast food is more the ‘fast’ than the ‘food’

AMS
Edmonton, Alberta

Slater J, Sevenhuysen G, Edginton B, & O’neil J (2011). ‘Trying to make it all come together’: structuration and employed mothers’ experience of family food provisioning in Canada. Health promotion international PMID: 21693474

I have previously blogged about the fact that in talking about the obesity problem, we spend more time talking about ‘what’ people do than ‘why’ they do it.

I, for one, am convinced that addressing ‘what’ people do, without addressing ‘why’ people do so, is unlikely to change behaviour or provide any meaningful solutions.

This is perhaps best exemplified by the problem with fast food - which, is often enough, blamed for its putative role in this epidemic.

I have tried to put this idea into the following video (subscribers will have to head to my site to see it).

Appreciate all comments,

AMS,
Edmonton, Alberta

Longtime readers may recall a post explaining why hunger makes you eat crap.

Understanding this, is an important principle to promote healthy eating and weight management (not necessarily the same).

To make this message somewhat easier to communicate, I produced this brief video, which hopefully brings this very simple but important point across (subscribers may have to visit my site to view this video).

Very much appreciate your comments and please feel free to repost.

AMS
Leipzig, Germany