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, conclude authors of a US study in this week's issue of THE LANCET.
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 1988--94.
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.
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).
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 4�5 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 and insulin resistance in young black and white adults.
Fast-food consumption can be linked to adverse health outcomes through plausible mechanisms, and results from other studies lend support to our findings.
In an accompanying commentary (p 4), Arne Astrup (RVA University, Copenhagen, Denmark), concludes: "Fast-food restaurants may argue that the evidence that customers are being super-sized by their meals is too weak.
Recently, some major fast-food companies have taken positive steps by launching new healthier choices, such as porridge for breakfast, and fruit and vegetables for desert.