The limitations of this study relate mainly to its observational nature, with the possibility of residual confounding precluding definitive conclusions about causality, and to reliance on self-reported diet and other lifestyle factors. Our conclusions are restricted to frequency of fast-food restaurant use because we were unable to analyse sufficiently the considerable range of
available fast-food items and their portion sizes. Nonetheless, our results might underestimate the true magnitude of the effect because of measurement error and thorough adjustment for many co variates that might be on the causal pathway—eg, food groups and nutrients. Furthermore, several analytical issues might have affected our results. Measurement error, if non differential,would tend to result in attenuated estimates of the strength of association between fast-food intake and the outcome variables. Similarly, analyses of changes are limited by floor and ceiling effects in that some people never eat fast food (so cannot decrease) or
eat most meals at fast-food restaurants (so cannot increase). These difficulties would also tend to attenuate noted relations compared with the true relation (such as would be observed in a clinical trial of investigator controlled increase or decrease in fast-food intake). Only
data obtained in the first and last CARDIA examination are included in the reported analyses. Omission of missing data or data from intermediate examination could bias the results. To address these issues data were also analysed by repeated measures regression analysis with SAS PROC MIXED (data not shown), which includes all examinations for which data are available for every individual and properly handles correlated
observations within individuals. Because the repeated measures regression analysis did not yield additional insights into the data beyond that presented in the tables, we did not present specific findings using that more complex methodology.In conclusion, 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.are included in the reported analyses. Omission of missing data or data from intermediate examination could bias the results. To address these issues data were also analysed by repeated measures regression analysis with SAS PROC MIXED (data not shown), which includes all examinations for which data are available for every individual and properly handles correlated
observations within individuals. Because the repeated measures regression analysis did not yield additional insights into the data beyond that presented in the tables, we did not present specific findings using that more complex methodology.In conclusion, 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.are included in the reported analyses. Omission of missing data or data from intermediate examination could bias the results. To address these issues data were also analysed by repeated measures regression analysis with SAS PROC MIXED (data not shown), which includes all examinations for which data are available for every individual and properly handles correlated
observations within individuals. Because the repeated measures regression analysis did not yield additional insights into the data beyond that presented in the tables, we did not present specific findings using that more complex methodology.In conclusion, 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.