Head to Head: Chips vs. Carrots?

A review on the role of energy density and food costs by Adam Drewnowski and SE Specter, reveals that there is an established relationship between the low cost of calorie-rich foods. People are getting higher percentage of their calories from energy dense foods (high in fat and sugar). Meanwhile the volume of food we eat has remained about consistent. Moreover, energy dense food are more palatable and influence preference of dietary tastes.

Over the past few decades, the cost of energy-dense foods has become very low. For instance, the energy cost of potato chips was about 20cents/MJ(1200kcal/$) while fresh carrots were about 95 cents/MJ(250kcal/$). Energy dense foods have been increasing in the mainstream diet readily over the past few decasdes, and cost for these foods has increased much slower than it has for healthier options of fruits and vegetables. Diets which include a lot of these energy dense, unhealthy options have been linked with higher risks of developing type 2 diabetes and obesity.

The review also revealed that income affects the quality of foods people eat, with higher SES groups having better quality diets. Food costs were found to be an issue for low income families as they spend a higher percentage of their disposable income on food.

This review demonstrates that there are broad factors at play when explaining the rise of the obesity epidemic. The study reveals that cost of food, access to income, how our palate and biopsychological dietary patterns develop based on the energy density of foods, confluence together to influence the rise in obesity!

How We Eat

As mentioned before fast food outlet density is related to increased risk of obesity. On the flipside, access to supermarkets offering a variety of high-quality products, especially at lower costs seems to be associated with a risk reduction in obesity. The review conducted by Dr. Nicole Larson et. al on neighbourhood environment and access to healthy foods found interesting results relating to this area.

- Each additional supermarket was related to a 32% increase in predominantly African-American communities and 11% increase in predominantly Caucasian in meeting fruits and vegetable guidelines.

- A study in the review also found that fruit and vegetable intake in kids was related to the distance between home and nearest convenience store.

- Residents of rural, low income, and minority communities were at higher risk of obesity due to poor access to supermarkets, healthy food stores, and other grocery stores.


Eating Out

What's interesting about the review was that it examined the patterns of  our dietary intake as well, and found that eating out at restaurants accounts for about half the US food expenditures(~$558 billion). Eating out, particularly at fast food restaurants, is associated with greater prevalence of obesity. In addition, restaurant meals tend to higher in calories and lower in nutritional quality, contributing to an unhealthy diet. I mentioned some of the relationships earlier, but Larson et. al have described studies that show a much more subtle dynamic at play with regards to placement of fast food restaurants and low income communities. Lower SES communities tended to have higher density of fast food outlets. In addition, richer communities had higher proportion of healthy food choices offered on their menus compared to lower SES communities.

These differences add up and contribute to how the obesity epidemic manifests itself in different communities!

Something Closer to Home

Although this might be beating the point that the built environment and SES impact risk factors for obesity to death, but the evidence was also replicated in Edmonton by Dr. Tanya Berry and others from University of Alberta.

Over a six year longitudinal study, the authors found that a younger age and living in a lower SES neighbourhood significantly predicted increased BMI. There was lower neighbourhood satisfaction and higher BMIs in communities with lower incomes. The study also found that the biggest gains in obesity were among young adults, between the ages 18-34.

However, longitudinally, the authors found little change between BMI and walkability of neighbourhoods. This was interestingly attributed to healthier people self-selecting more walkable neighbourhoods, which means that longitudinally there would be low impact on BMI changes. There were components to lower socioeconomic neighbourhoods that contributed to increased obesity.

Socioeconomic status and Obesity

There seems to be a lot of work done on low SES status influences obesity. There are some good systematic reviews, such as one by Dr. Lindsay McLaren from Calgary and one put out by the World Health Organization on the influence of SES indicators on obesity. 

The research indicates that there is a shift from lower income countries to higher income countries as to how the different quartiles of the population which are affected by obesity. In lower to middle income countries, there is a higher association of developing obesity in the top quartiles of society. Meanwhile, in developed countries, there was a higher association of obesity with the lower SES quartiles.

Interestingly, the study found this trend more pronounced among women. According to the WHO review, "Obesity was significantly more common among women of higher SES in all low-income economies and more common among women of lower SES in all upper-middle-income economies."

The data also indicates that in the developing world, as economic growth takes place, the lower quartiles are earilest affected with increases in obesity rates. This is especially concerning as some of the economic indicators for many nations around the world rise, there is an associated rise of chronic diseases like obesity taking place with that. Dr. Mclaren partly attributes this to the barriers of healthy lifestyles in the lower income quartiles even in the face of economic prosperity coupled with sociocultural value placed on large body types in lower SES communities in low income countries.