Background: We proposed to examine trends in modifiable behaviorally related cancers among younger men and women in the United States. Methods: Alcohol-associated cancers, HPV-associated, obesity-associated, physical inactivity-associated, and tobacco-associated were defined using ICD-O-3 site codes. From 2001 and 2017, registry data were obtained from the United States Cancer Statistics database. SEER*Stat 8.3.8 and Joinpoint regression program 4.8.0.1 were used to calculate the trends of associated cancers expressed per 100,000. Results: Of the young women (ages 20-49 years) the incidence of cancers in 2017 associated with alcohol, smoking and obesity were 89/100,000, 43/100,000 and 64/100,000 respectively. Based on analysis of trends of women from 2001 to 2017, obesity, physical inactivity and alcohol related cancers increased with an annual percent change (APC 2.31%, 1.67%, 0.46%, p < 0.001). Using a projection model, in Hispanic women, obesity related cancers will become the highest incidence cancers by 2035, surpassing alcohol and physical inactivity. Of the young men (ages 20-49 years) the incidence of cancers in 2017 associated with alcohol, obesity, and tobacco were 23/100,000, 36/100,000 and 44/100,000 respectively. On trends analysis, obesity, physical inactivity, and alcohol related cancers have increased (APC 2.0%, 1.65%, 0.17%, p < 0.001, p < 0.001, p = 0.044), whereas tobacco-related cancers are decreasing with an APC of -0.44% (p < 0.001). When examining different regions, the highest APC for obesity and physical inactivity related cancers was 2.43% in the Midwest (p < 0.001). Using a prediction model, obesity is predicted to surpass alcohol and physical inactivity related cancers for men 20-49 years old by 2035. Conclusions: In women, most modifiable factors associated with cancer are increasing except in HPV related cancers. In men, these rates of cancer are increasing except in tobacco related cancers. However, rates of obesity related cancers are on the rise in Hispanic women and younger men in southern U.S. regions. Obesity is projected to become the major modifiable factor for many associated cancers.