A case-control study among Singapore Armed Forces' newly enlisted Servicemen was conducted to examine factors associated with male obesity. Four hundred and fifty-nine individuals from the Obese Basic Military Training program were selected as "cases" (average age: 19.5, body mass index: 30.4) and another 340 individuals were selected from the Normal Basic Military Training program as "controls" (average age: 19.3, body mass index: 21.4). Information such as family background, socioeconomic factors, and lifestyle practices were captured using facilitator-led questionnaires. Several variables were significantly associated with obesity after adjustments for possible confounders. These include childhood obesity (odds ratio [OR] = 2.06), less than an hour of exercise per day (OR = 2.97), Indian ethnicity (OR = 2.22), specific education backgrounds (especially that of Institute of Technical Education-OR = 2.75), father's employment at nonmanagerial/professional jobs (OR = 1.52), mother's employment at managerial/professional jobs (OR = 2.02), regular smoking (OR = 1.73) and alcohol consumption (OR = 2.26), 6 hours or less of sleep (OR = 3.73), obesity among family members (OR = 1.86 for mother; OR = 2.98 for siblings), parental history of diabetes mellitus (OR = 2.22 for father; OR = 2.70 for mother), and eating at inexpensive local food stalls (OR = 1.82). Our study found that a number of factors, ranging from personal and family backgrounds to lifestyle choices, were significantly associated with obesity among male youths.