Fig 1.
The trend of the obesity prevalence rate within period-age, cohort-age and period-cohort for both sexes.
It should be noted that in these plots, each age and period group represent an interval of 5 years; for example, the period 1980 would be converted to 1980-1984. Based on the upper left plot, regardless of the time period, the age distribution of obesity prevalence has similar trend patterns. The top middle plot shows the trend of obesity prevalence in different cohort groups as they age through the time course. The upper right plot shows the trend of obesity prevalence for different cohorts during each period. Based on this plot, a vertical shift can be seen in the increasing periods. However, there is no significant difference in the shape of the trend line for each period. The lower left plot shows the trend for each age group as the period increases. Based on this plot, each age group had a higher prevalence of obesity compared to the previous period. The lower middle plot shows the trend for the same age groups of different cohorts. For example, the trend of the age group 20, born around 1970, had a lower prevalence compared to the 20s, born around 1980. Finally, the lower left plot shows the change in the trend of obesity prevalence for each cohort group over time. It can be seen that for the majority of cohorts, with the exception of the 1905 and 1915 cohorts, the rate increased after each period.
Fig 2.
The chart in the top-left corner indicates that the age distribution of overweight individuals has largely remained consistent over time, irrespective of the period.
In the top-middle chart, the overweight prevalence trends within different cohorts as they get older through the study course. The top-right chart presents the trends in overweight prevalence for various cohorts within different periods. Here, a noticeable shift in the starting point of each trend line can be observed as time progresses. However, the overall shape of the trend lines remains largely unchanged across the different periods. The bottom-left chart depicts how the trends for each age group progress with increasing periods. It demonstrates that every age group shows a higher prevalence of overweight individuals compared to previous periods except for the age group of 70s in period of 1990 which showed a slight decline comparing to the previous period. In the bottom-middle chart, the trends for the same age groups across different cohorts are compared. For example, individuals aged 40s who were born around 1940 exhibit lower prevalence rates compared to those in the same age bracket born in 1970. Lastly, the bottom-right chart highlights how overweight prevalence trends have evolved for each cohort over time. It indicates that, similar to obesity trends, most cohorts, excluding those from 1905 and 1915, have experienced an increase in rates over subsequent periods.
Table 1.
Comparison of different models to Age-Period-Cohort model as reference for obesity prevalence in the world.
A Poisson model was fitted to data.
Fig 3.
Plots of the results of the APC model fit to global obesity prevalence.
The blue dashed and red dotted lines are one and two standard errors around the zero, respectively. The plots in the top row show the canonical coefficients of each time-varying parameter. These coefficients explained the effect of the double difference of each effect on the trend, which was further translated into the acceleration or growth rate of the effect. On the other hand, the bottom row showed the normalized effect. The normalization was done on the basis of the first and the last value of the parameters.
Table 2.
Comparison of different models to Age-Period-Cohort model as reference for overweight prevalence in the world. A Poisson model was fitted to data.
Fig 4.
Plots of the results of the APC model fit on global overweight prevalence.
The plots A to C clarified how the double difference of each effect influenced the trend. Conversely, the bottom row displayed the normalized effect of each time varying parameter, achieved by standardizing the values based on the initial and final parameters.