Elsevier

The Lancet

Volume 365, Issue 9453, 1 January 2005, Pages 36-42
The Lancet

Articles
Fast-food habits, weight gain, and insulin resistance (the CARDIA study): 15-year prospective analysis

https://doi.org/10.1016/S0140-6736(04)17663-0Get rights and content

Summary

Background

Fast-food consumption has increased greatly in the USA during the past three decades. However, the effect of fast food on risk of obesity and type 2 diabetes has received little attention. We aimed to investigate the association between reported fast-food habits and changes in bodyweight and insulin resistance over a 15-year period in the USA.

Methods

Participants for the CARDIA study included 3031 young (age 18–30 years in 1985–86) black and white adults who were followed up with repeated dietary assessment. We used multiple linear regression models to investigate the association of frequency of fast-food restaurant visits (fast-food frequency) at baseline and follow-up with 15-year changes in bodyweight and the homoeostasis model (HOMA) for insulin resistance.

Findings

Fast-food frequency was lowest for white women (about 1·3 times per week) compared with the other ethnic-sex groups (about twice a week). After adjustment for lifestyle factors, baseline fast-food frequency was directly associated with changes in bodyweight in both black (p=0·0050) and white people (p=0·0013). Change in fast-food frequency over 15 years was directly associated with changes in bodyweight in white individuals (p<0·0001), with a weaker association recorded in black people (p=0·1004). Changes were also directly associated with insulin resistance in both ethnic groups (p=0·0015 in black people, p<0·0001 in white people). By comparison with the average 15-year weight gain in participants with infrequent (less than once a week) fast-food restaurant use at baseline and follow-up (n=203), those with frequent (more than twice a week) visits to fast-food restaurants at baseline and follow-up (n=87) gained an extra 4·5 kg of bodyweight (p=0·0054) and had a two-fold greater increase in insulin resistance (p=0·0083).

Interpretation

Fast-food consumption has strong positive associations with weight gain and insulin resistance, suggesting that fast food increases the risk of obesity and type 2 diabetes.

Introduction

The frequency of obesity has risen at an alarming rate in all age and ethnic groups in the USA.1, 2 The age-adjusted prevalence of obesity, defined as a body-mass index (BMI) of 30 kg/m2 or greater, was 30·5% in 1999–2000 compared with 22·9% in 1988–1994, with even higher rates in ethnic minority groups.1 About two of every three US adults and four of five African-American women were overweight or obese in 1999–2000.1 In children and adolescents, the prevalence of being overweight rose by 50% in the past decade to about 15%.2

The medical and economic outcomes of excessive bodyweight are great, including an estimated 300000 excess deaths and at least US$100 billion per year in medical expenditures.3, 4, 5, 6 One particularly ominous public-health issue is the occurrence of glucose intolerance7 and type 2 diabetes in obese adolescents and young adults.8

Because of its rapid development in genetically stable populations, the obesity epidemic can be attributed to environmental factors affecting diet, or physical activity level. One potentially important dietary factor is consumption of fast food, which can be defined as convenience food purchased in self-service or carry-out eating places.9, 10 From its origins in the 1950s, fast food has grown into a dominant dietary pattern, with a current estimate of about 247115 restaurants in the USA.11 Consumption of fast food by children has risen from 2% of total energy in the late 1970s to 10% of energy in the 1990s.12

Several factors inherent to fast food as it now exists could promote a positive energy balance11, 13 and thereby increase risk for obesity and diabetes, including: excessive portion size, with single large meals often approaching or exceeding individual daily energy requirement; palatability, emphasising primordial taste preferences for sugar, salt, and fat; high energy density;14 and high glycaemic load. Several dietary factors such as trans-fatty acids15 and high glycaemic load16 might also enhance risk for diabetes through energy-independent mechanisms.

Surprisingly few studies have investigated the effects of fast-food consumption on energy balance or bodyweight,17, 18, 19, 20 and most of these are of cross-sectional design. To our knowledge, no data for fast-food consumption and diabetes-related endpoints are available. For these reasons, we aimed to investigate the association between reported fast-food habits and changes in bodyweight and insulin resistance over a 15 year period in young black and white adults in the USA.

Section snippets

Methods

The Coronary Artery Risk Development in Young Adults (CARDIA) study is a multicentre, population-based prospective study of cardiovascular disease risk factor evolution in a US cohort of African-American and white young adults. The four study centres are Birmingham, AL, Chicago, IL, Minneapolis, MN, and Oakland, CA.

Results

5115 people attended the baseline examination, with 74% retention of the surviving cohort in year 15. Those who were not in the 15-year cohort were younger (mean 24·2 years [SD 3·7] vs 25·1 years [3·6], p<0·0001) and more likely to be black (62·9% vs47·1%, p<0·0001), men (49·1% vs44·1%, p=0·0014), and have less education (61·0% vs 80·9%, p<0·0001) at baseline, but they did not differ by BMI (mean 24·4 kg/m2 [SD 5·2] vs 24·5 kg/m2[5·0], p=0·2287) or frequency of fast-food visits (2·1 times a

Discussion

In young adult black and white men and women living in the USA between 1985–86 and 2000–01, we recorded strong positive associations between frequency of visits to fast-food restaurants and increases in bodyweight and insulin resistance, the two major risk factors for type 2 diabetes.27 By comparison with the average 15-year weight gain in participants with infrequent fast-food restaurant use at year 0 and follow-up, those with frequent fast-food restaurant use at both baseline and follow-up

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