U.S. Study Highlights Clear Link Between Increased Fast-food Consumption And Obesity

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. 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 18–30 years in 1985–86) 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 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 view of the high and increasing rates of fast-food consumption, further research into the effects of this dietary pattern on public health should be given priority."

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. But should customers not be given the benefit of the doubt? Appropriate action would be to reduce portions to normal sizes, and to sell burgers of lean meat, whole-grain bread or buns, fat-reduced mayonnaise, more vegetables, lower-fat fried potatoes, and reduced-sugar soft drinks. Although the price may be increased, at least such changes in fast-food meals can have no adverse health-effects. 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. I hope that this trend continues."