Obesity is increasing in the USA; at the turn of the millennium around 30% of Americans were clinically obese (having a body-mass index of 30 kg per metre squared or more) compared with 23% of the population during the period 198894. Obesity causes an extra 300,000 deaths among Americans and health-care costs of $100 billion each year. The effect of fast food on risk of obesity and type 2 diabetes has received little attention. Mark A Pereira (University of Minnesota), David S Ludwig (Childrens Hospital Boston), and colleagues investigated the association between reported fast-food habits and changes in bodyweight and insulin resistance over a 15-year period in the USA.

Over 3000 young (age 1830 years in 198586) black and white adults were followed up with repeated dietary assessment. Overall, white women consumed less fast food (average 1.3 visits to a fast-food restaurant per week) than other ethnic groups (average 2 visits per week). Change in fast-food frequency over 15 years was directly associated with changes in bodyweight in white individuals; a weaker association was recorded among black people. Increases in fast-food consumption was associated with increased insulin resistance in both ethnic groups.

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 (203 individuals), those with frequent (more than twice a week) visits to fast-food restaurants at baseline and follow-up (87 individuals) gained an extra 45 kg of bodyweight and had a 2-fold greater increase in insulin resistance.

Dr Ludwig comments: "fast-food habits have strong, positive, and independent associations with weight gain
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Contact: Joe Santangelo
j.santangelo@elsevier.com
1-212-633-3810
Lancet
30-Dec-2004