Is candy eating a way to control body weight?

T he increasing prevalence of overweight and obesity has called for actions already in place for years. Unfortunately, the results so far have been mostly disappointing. The role of science in combating obesity is to provide evidence for decision-making at political (national and local) level, in food industry, in health care settings and in educational planning. Evidently, more data are needed to understand the detailed aetiology of obesity and how to combat obesity at population and individual levels. In addition to physical activity, diet is a major factor affecting energy balance and subsequently weight change. Most of the studies looking at the impact of diet on weight change have concentrated on the proportions of macronutrients (as percent in total energy intake, E%) or on consumption of specific foods. Recently, several systematic reviews and meta-analyses have addressed the role of carbohydrates in obesity. Cross-sectional studies tend to show an inverse relation between the proportion of dietary carbohydrates (E%) and obesity (1). In contrast, cohort studies and randomised intervention trials do not provide strong evidence that increasing or decreasing the proportion of dietary carbohydrates has a significant independent effect on body weight maintenance (1). Sugar-rich foods are usually low in dietary fibre and at least moderately high in energy density. In theory, both properties could link high sugar intake with obesity. In an extensive narrative review, van Baak and Astrup (2) concluded that there is insufficient evidence that an exchange of sugar to nonsugar (starchand/or fibrerich) carbohydrates would assist in body weight reduction. Very few population studies report on the association between sugar-rich food intake and weight gain. In a study using the EPIC cohort in Potsdam, Schulz et al. (3) reported that intake of high sugar foods, i.e. sweets, was significantly predictive of large weight gain. However, there is stronger epidemiological (1, 2) and less consistent evidence from randomised intervention trials (4) that sugar-sweetened beverages may induce obesity. Since the data on the role of carbohydrate on the development of obesity are still inconclusive, more research on this topic is warranted. Therefore, studies like the one published in Food and Nutrition Research on the association of candy consumption on body weight (5) might give some new insights into this important issue. O’Neil et al. (5) have had access to a large data set, a total of 7,049 children and 4,132 adolescents from the National Health and Nutrition Examination Survey (NHANES). By using one 24-hour dietary recall, they divided the participants into two groups: candy consumers and nonconsumers. Energy intake was higher in candy consumers, but after adjusting for gender, ethnicity, age and energy intake, the consumers’ mean weight was significantly lower by 1.4 kg. The authors concluded that candy consumers were less likely to be overweight than nonconsumers. The large number of participants in the study of O’Neil et al. (5) is a definite strength, and the authors should be praised for carrying out their research. However, one needs to be somewhat careful with the interpretation and practical implications of their main finding. There are several methodological and even philosophical reasons for this request. First, the authors used one 24-hour recall to dichotomise participants into consumers and nonconsumers. Although a 24-hour recall may very well indicate the mean intake of group level, day-to-day variations in food intake decrease the reliability on individual level (6). It is likely that both ‘heavy-users’ and ‘never-users’ of candy are classified correctly by the 24-hour recall. In contrast, the extent of misclassification among all other participants can only be guessed. Misclassifications tend to preclude from finding significant associations, that is, they increase the likelihood for type II errors. Another methodological concern is related to the adjustments. Since changes in weight should reflect energy balance, energy intake must be considered a major factor. This leads to the question, whether adjustment for energy intake is warranted? The concern on adjusting for energy intake is emphasised by looking at the results: according to data with adjusting only for gender, ethnicity and age, energy intake was significantly higher in candy consumers. The difference in mean intake (9.4 vs. 8.3 MJ/day) was not only statistically significant: if a difference of this magnitude is real, it ought to be associated with energy balance. However, when the outcome was changed to weight, and energy intake was included as covariate, the weight difference between consumers and nonconsumers was favouring consumers. The third concern is more philosophical: a majority of studies assessing the relationships between diet and