Obesity is an important global public health challenge, as it is a major risk factor for cardiovascular and chronic diseases, with major impact on morbidity, mortality, and health care costs. Effective management of obesity includes prevention of premature death and disability, reducing the economic burden of disease, and the promotion of healthy diets and lifestyles 29,48.
With respect to the promotion of healthy diet and lifestyle, our aim was to analyze global dieting and weight loss trends, being cognizant that sociocultural, societal, and traditional practices could potentially play a role. Since dieting and weight loss pursuits are a global enterprise, with the Internet a major portal for disseminating information and advertisements, we considered Big data analysis ideal for studying this vast amount of data on global dieting practices and trends 49–51. No attempt was made to exclude fad diets and weight loss programs, even though these also have potential health risks, including increased risks of eating disorders, mental health problems, including stress, anxiety, and depression.52–54 32,55−60.
In this study, we found that the search volume for the Northern and Southern Hemisphere diets was the highest in January, which coincides with the New Year, where people traditionally make New Year’s resolutions following the Christmas holidays and festivities. On the other hand, for the predominantly Arab and Muslim countries, the highest search volumes were in April. For South Korea, the highest search volume was in February.
On cosinor analysis, which analyzes periodic trends, online search interest in dieting in the Northern Hemisphere was statistically significantly seasonal, but for the Southern Hemisphere, it was not.
Studies using cosinor analysis tend to show opposite dieting trends of Southern compared to Northern Hemisphere countries 46,61, probably reflecting the divergent seasons. The data on global seasonal trends in dieting is apparently limited, but studies on weight changes in three major countries, including Japan, the United States, and Germany, showed a sharp increase from December, with the greatest increase in weight in early January, just after the Christmas holiday festivities 62,63.
In this study, the search volumes of both Northern and Southern Hemispheres were the highest in January. Overall, search interest reached its peak before summer (April) in the Northern Hemisphere, and November in the Southern Hemisphere 64–66. For predominantly Arab and Muslim countries, seasonality was not striking, and the magnitude was smaller than that observed for the Northern Hemisphere, with April being the highest point in the periodic rate. Seasonality tended to be a bit more pronounced in the liberal Arab and Muslim countries, compared to their more conservative counterparts.
Finally, in South Korea, data from Naver showed seasonality, with April being the peak month for online diet searches, with the trend of rhythm being similar to that of the Northern Hemisphere. However, there was no statistically significant seasonality in the data from Google, which may be a reflection of the lower percentage of Google searches on this topic in South Korea. Because of this skew, such Google searchers on the subject was most likely unrepresentative.
Although our study is exploratory, our Big-data analyses could suggest the potential for seasonal emphasis on weight control programs. More-cost effective health awareness and prevention weight loss strategies could harness the power of online Big-data analyses and real-time “nowcasting”, for optimal timing of public health interventions for obesity. In the same way that marketing strategists use such Big data to target consumers, so too could public health authorities utilize Big data for optimal timing of public education and intervention programs.
Strengths and limitations
The authors are unaware of any previous studies to analyze the global seasonality of diets using social big-data. Big-data analysis of seasonal dieting trends is rather easy to access and analyze, and therefore potentially more cost-effective. This approach can also hold relevance to other areas of public health.
Our study has clear limitations. Firstly, we conducted the keywords search terms in English only, which is less representative for countries that do not use English as their primary search language, such as in South Korea and in the Arab and Muslim -majority countries we studied. It may therefore be more accurate to include searches using the preferred language of such countries. Secondly, it is difficult or near impossible to examine the individual characteristics of each person who performed each search, without breaching social media confidentiality or other agreements. Thirdly, we could not accurately predict the actual figures by analyzing the search volume using web-based methods only.