Measuring the Effect of Ending Food Deserts in Obese Children
By Ellen Feldman, MD
Altru Health System, Grand Forks, ND
Summary Points
- Food Retail Expansion to Support Health (FRESH) in New York City provides funds to renovate or establish new supermarkets designed to enhance access to affordable and healthy foods in select, low-income neighborhoods.
- This study compares specialized body mass index (BMI) scores (adjusted for age of child: BMIz) and analyzes the likelihood of obesity for public school students residing within 0.5 miles of a FRESH supermarket compared to a control group of students living farther from the market, but still within a targeted neighborhood.
- Follow-up over 12 months after the opening of a FRESH supermarket reveals a small but statistically significant drop in BMIz scores in the cohort (students living within 0.5 miles of the store) compared to the control and a 1% drop in the likelihood of obesity in this same group.
SYNOPSIS: A study of New York City students followed for 12 months after the opening/remodeling of a grocery store incentivized to provide healthy food options finds a small but significant decrease in body mass index scores and a decrease in the likelihood of obesity in the students living within walking distance to the store compared to a control group of peers living farther from such a store.
SOURCE: Rummo P, Sze J, Elbel B. Association between a policy to subsidize supermarkets in underserved areas and childhood obesity risk. JAMA Pediatr 2022;176:646-653.
The American Medical Association’s recognition of obesity as a chronic, complex disease in 2013 was a pivotal moment in the fight against it.1 This recognition opened the door to new research regarding the prevention and treatment of obesity.1,2
The new status as a disease reflected an understanding of the complex, multifactorial causes of obesity and the awareness that obesity is a significant comorbidity that influences the course of many other chronic diseases, including specific cancers, metabolic diseases, cardiovascular diseases, arthritic diseases, and endocrinologic disorders. With this recognition, public health measures to target early prevention of obesity are emerging, but the prevalence of obesity in the United States continues to grow, especially in areas of with higher poverty levels and lower socioeconomic status.1-4
Primary prevention of obesity starts at a young age. There is research suggesting that food deserts (neighborhoods where it is difficult to purchase affordable, healthy foods) contribute to the risk of obesity.4,5 Efforts have been made to encourage supermarkets that carry a wide variety of healthy products to open in disadvantaged areas.
Studies on the effects of opening such markets are limited at this point, and the results are mixed. Some show a reduction in the purchase of items such as sugar-sweetened beverages, while others show no change in either diet or body mass index (BMI) in consumers.5,6
The focus of this study centered around a New York City (NYC) program — Food Retail Expansion to Support Health (FRESH) — which has a goal of enhancing access to fresh and affordable foods in low-income neighborhoods by providing tax and other incentives for opening and/or renovating supermarkets.7
Notably, each supermarket receiving funding under this program has specific requirements for space devoted to perishable items and fresh produce.7 Eight new or renovated FRESH supermarkets in eight different NYC neighborhoods were included in this analysis.
Rummo et al wanted to evaluate whether there was an association with a change in BMI in students living within walking distance of a FRESH supermarket compared with students living in a “FRESH-eligible” low-income area but residing more than 0.5 miles from the supermarket itself. In this quasi-experimental approach (i.e., nonrandomized study), Rummo et al used public school data providing the height and weight of children in grades K-12 for the 12 months prior to a supermarket opening or reopening after renovation and 12 months following such an event.8
To address confounding variables, only data from students with stable addresses during the time of the study (2009-2016) were included. Additionally, only students with height and weight data collected at school prior to and after the supermarket openings were included. These measurements were converted to BMIz scores, which consider age and sex along with height and weight.9 For purposes of this study, a BMIz score at or above the 95th percentile was classified as obese.
Using these criteria, 11,356 students qualified for the intervention group (living within 0.5 miles from a new or renovated FRESH supermarket) and 43,372 students living within an identified area of low income but farther than 0.5 miles from the FRESH supermarket were identified for a control group. Interestingly, BMIz scores and percentage of obesity fell in both groups from baseline to follow-up.
While there was a statistically significant drop in BMIz scores among students in the intervention group compared to the control arm (see Table 1), this drop represented only a small effect size, with mean BMIz scores dropping from 0.75 pre-intervention to 0.70 post-intervention in the intervention group (students living within 0.5 miles from the designated grocery store). Notably, BMIz score drops of much higher magnitude (0.15 to 0.20) typically are necessary to affect clinical change.10
Table 1. Treatment and Control Arm Data for Supermarket Renovation and Obesity Rates |
||
| BMIz Score | % Obese | |
Treatment group pre-supermarket opening/renovation |
0.75 (SD 1.15) |
24.3 (SD 42.9) |
Treatment group post-supermarket opening/renovation |
0.70 (SD 1.15) |
23.3 (SD 42.3) |
Control group pre-supermarket opening/renovation |
0.75 (SD 1.10) |
23.3 (SD 42.3) |
Control group post-supermarket opening/renovation |
0.74 (SD 1.10) |
23.3 (SD 42.3) |
Difference-in-differences estimate |
-0.04 (95% CI; 0.06-0.02), P < 0.01 |
-0.01 (95% CI; 0.02-0.002), P < 0.001 |
BMIz: age-adjusted body mass index; SD: standard deviation; CI: confidence interval |
||
Other analyses included:
- The likelihood of obesity among students living close to a new FRESH supermarket vs. living near a renovated FRESH supermarket: no statistical association with change in BMIz scores or likelihood of obesity found.
- The likelihood of obesity if a new non-FRESH supermarket opened within walking distance as well as a FRESH supermarket: no statistical association with change in BMIz scores or likelihood of obesity for these students.
- When results of the cohort were looked at according to grade, there was a stronger association with decreases in BMIz scores and likelihood of obesity in students from grades K-8 vs. students in high school, although the effect size remained low overall.
COMMENTARY
The intersection of medicine, public health, and public policy are well-illustrated in this analysis of the effect of government-subsidized supermarkets on development and prevention of a major medical condition (obesity) in children. Additionally, the complications and confounding factors inherent in such undertakings are highlighted.
The results are far from impressive; Rummo et al noted that, although the changes found in BMIz scores are promising, they are unlikely to be clinically meaningful and that supermarket subsidies may “be most effective in tandem with other policies.”
A companion editorial in the same issue in the Journal of the American Medical Association takes an even less optimistic look and notes, “our reading of the results of this study is that they are far more consistent with trivial to zero effects than promising.”11
While the results of this study may be subject to interpretation, it does seem clear that there is more work to be done on understanding the multifactorial drivers of obesity and translating these to effective public policy initiatives. It may be that individualized approaches are most meaningful, that longer-term follow-up is needed, and that interlocking and overlapping interventions are required to effectively prevent the development of obesity.
While Rummo et al were able to use public school measurements to determine BMIz scores and stable addresses, they were not able to verify any direct changes in diet associated with the opening or renovating of a FRESH supermarket. It is notable that BMIz scores changed more in the younger students; this may have to do with more significant parental influences on purchasing food for this age range than for high schoolers. Future studies looking at obesity preventions may want to include factors such as age and changes in eating habits.
This study, even with limitations, emphasizes the important role of medical research in objectively analyzing the effect of public programs and can serve as a reminder to the primary care provider to discuss availability of fresh, affordable food with patients, especially those in more vulnerable areas.
REFERENCES
- Kyle TK, Dhurandhar EJ, Allison DB. Regarding obesity as a disease: Evolving policies and their implications. Endocrinol Metab Clin North Am 2016;45:511-520.
- Katz DL, O’Connell M, Yeh M-C, et al. Public health strategies for preventing and controlling overweight and obesity in school and worksite settings: A report on recommendations of the Task Force on Community Preventive Services. MMWR Recomm Rep 2005;54:1-12.
- Tiwari A, Balasundaram P. Public health considerations regarding obesity. In: StatPearls [Internet]. StatPearls Publishing;2022.
- Hu K, Staiano AE. Trends in obesity prevalence among children and adolescents aged 2 to 19 years in the U.S. from 2011 to 2020. JAMA Pediatr 2022;e222052. doi: 10.1001/jamapediatrics.2022.2052. [Online ahead of print].
- Gopika G, Raghuveer V, Krishna V. A mini-review: Everything you need to know about food deserts. J Environ Sci Public Health 2022;6:65-68.
- Zhen C. Food deserts: Myth or reality. Annu Rev Resour Economics 2021;13:109-129.
- New York City Economic Development Corporation. Finance solutions: Food Retail Expansion to Support Health (FRESH). https://edc.nyc/program/food-retail-expansion-support-health-fresh
- Harris AD, McGregor JC, Perencevich EN, et al. The use and interpretation of quasi-experimental studies in medical informatics. J Am Med Inform Assoc 2006;13:16-23.
- Inokuchi M, Matsuo N, Takayama JI, Hasegawa T. BMI z-score is the optimal measure of annual adiposity change in elementary school children. Ann Hum Biol 2011;38:747-751.
- Freedman DS, Butte NF, Taveras EM, et al. Longitudinal changes in BMI z-scores among 45,414 2-4-year-olds with severe obesity. Ann Hum Biol 2017;44:687-692.
- Deemer SE, Owora AH, Allison DB. Taking a hard look at the empirical evidence for popular community-based interventions in obesity. JAMA Pediatr 2022;176:639-641.
A study of New York City students followed for 12 months after the opening/remodeling of a grocery store incentivized to provide healthy food options revealed a small but significant decrease in body mass index scores and a decrease in the likelihood of obesity in the students living within walking distance to the store compared to a control group of peers living farther from such a store.
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