IMPACT OF OBESITY ON FUTURE INCIDENCE OF MALIGNANCIES IN YOUNG ADULTS

Purpose: In addition to many other adverse health consequences of obesity, morbid obesity is associated with increased risk of certain cancers.  In this work, we created a stochastic model to depict the annual incidence of cancers in a cohort of 20 year old US adults.  Using the model, the impact of the rate at which individuals become obese on cancer incidence was measured.

Method: Separate models were created for 20 year old men and women.  Model input variables were extracted from a variety of published sources including.  At age 20, 7% of men and women are morbidly obese (body mass index > 35).  The prevalence of morbid obesity would increase by 3% annually until the cohort reached 50 years of age.  The model output included the numbers of death and new cancer cases each year until the cohort reached the age of 80.  The main predictor variable was the rate at which the prevalence of morbidy obese increases. 

Result: The initial cohort started with 4.5 million 20 year olds as of 2010, including 2.2 million women and 2.3 million men.  In the table, the cumulative number of incident cancers was 821,600 in women and 1,032,900 in men, with 16.1% and 13.5% of those cancers arising in morbidly obese women and men, respectively.  If the rate of obesity increase could be reduced from 3% to 1% per year, the number of cancers would decrease by 10,100 in women and by 3,600 in men.  The decrease in the number of cancer cases among the obese would be larger (38,300 in women and 41,100 in men).  On the other hand, if the rate of increase in obesity accelerated to 5% per year, there would be 9,700 additional cases of cancer in women and 3,400 in men. 

	F	M
# surviving at age 80	1,366,000	1,072,000
Peak prevalence of obesity	12.6%	12.3%
Total number of cancers	821,600	1,032,900
Cancers among the obese	132,700	139,900
Cancers among the non-obese	688,900	893,000
% Cancers occurring in the obese	16.1%	13.5%

Conclusion: While weight reduction is notoriously difficult in persons who are already obese, preventing young adults from becoming from obese is more achievable.  Such an effort will not only decrease the burden of morbidity commonly associated with obesity, but also substantially reduce the number of cancers.