Human Limits

Exploring performance and health with Michael J. Joyner, M.D.

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Obesity vs Fast Food Availability

Most people who read this blog probably don’t have to be convinced about the link between eating a lot of fast food and obesity.   However, I wanted to find out just how big the link is and see what else I could learn about this relationship.   Here are some interesting findings.


BMI vs. Healthy Food Outlets in NYC.

The figure below is from a study in New York City on the density of healthy eating options vs. BMI.  It tracked about 13,000 people and rated the density and quality of food outlets (supermarkets vs. fast food etc.) in their neighborhoods, rated them, and then divided the food ecology into quintiles (fifths).  The study also corrected for things like neighborhood walkability and other factors known to influence body weight in the population.   A person of average height living in the healthiest food neighborhoods (5th quintile) would weigh about 5-8 pounds less than a person living in the worst neighborhoods (1st quintile).   Depending on your perspective, that might not seem like a lot but either losing or gaining just a few pounds can have marked effects on things like your blood sugar and blood pressure.




 What about LA?

Los Angeles is very different than New York City.   This is especially true in terms of dependence on cars and the presence or absence of convenient public transportation.   So, what is the relationship between fast food restaurant density, driving and body weight in LA? 


“ Car owners have higher BMIs than non-car owners; however, individuals who do not own cars and reside in areas with a high concentration of fast food outlets have higher BMIs than non-car owners who live in areas with no fast food outlets, approximately 12 lb more (p = 0.02) for an individual with a height of 5 ft. 5 in. Higher restaurant density is associated with higher BMI among local residents. The local fast food environment has a stronger association with BMI for local residents who do not have access to cars.”


Driving and Fast Food Signs.

As noted above car owners in LA have higher BMIs than non-car owners.  The obvious explanation for this is that they are less physically active and that sitting in a car contributes to weight gain over time.  However, we all see road signs while driving.  Does the presence or absence of road signs influence body weight?  A very creative study on this topic found that:


“The higher the percentage of outdoor advertisements promoting food or non-alcoholic beverages within a census tract, the greater the odds of obesity among its residents, controlling for age, race and educational status. For every 10% increase in food advertising, there was a 1.05 (95% CI 1.003 – 1.093, p<0.03) greater odds of being overweight or obese, controlling for other factors. Given these predictions, compared to an individual living in an area with no food ads, those living in areas in which 30% of ads were for food would have a 2.6% increase in the probability of being obese.”


This data adds to all sorts of information showing that “marketing works”.  What we see while we drive makes a difference.


What Happens if Fast Food Outlets are Restricted?

The data above provide pretty good evidence that the type of food outlets, driving and advertising influence body weight and are contributing to the obesity epidemic (no big surprises here).  However, cities can regulate how many fast food restaurants there are and where they are located via zoning and licensing.   If the density of fast food restaurants were reduced what would the impact be?  This is especially important because many poor neighborhoods are so-called healthy “food deserts” and obesity is an especially big problem in these areas.   The interactions between income, neighborhood walkability, and the type of food outlets are complicated.  However, small changes in the local food and walking ecology can make a big difference in obesity statistics and ultimately public health.



There is a lot of discussion about “soda taxes”, expect to hear more about advertising and efforts to regulate fast food outlets in the coming years as public health efforts to attack the obesity epidemic accelerate.


One Response to “Obesity vs Fast Food Availability”

  1. March 15th, 2013 at 2:50 pm

    bk says:

    isn’t it possible that fast food restaurants tend to locate where there are more customers, so rather than being the cause of the obesity its more a result of it?

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