Objective To specify the age- and gender-specific, and the Body Mass Index (BMI) prevalence of Type 2 Diabetes Mellitus (T2DM) patients in Preah Kossamak Hospital, Phnom Penh, Cambodia. Methods The data of 1000 T2DM patients from 2010 to 2012, 609 females and 391 males was recorded. The age- and gender-specific prevalence of T2DM was divided into female and male patients respectively, and was based on specific age groups: < 25, 25~34, 35~44, 45~54, 55~64, and > 65 years old. The BMI values for Asians were used, < 18.5 (underweight), 18.5~22.9 (normal), 23~24.9 (overweight), and > 25 (obese). Results The 2 highest prevalence of T2DM is in 55~64 and > 65 age groups, in both male and female patients. However, the prevalence is higher in females than males. The percentage of female patients in 55-64 age group is 39.57%, whereas it is only 35.55% in males. There is 40.89% of female patients in > 65 years-old age group, which is also higher than the percentage of male patients, 33.25%. Moreover, the result delineates that the highest BMI group in both genders is > 25, yet males appear to be more obese than females. As compared to the percentage of BMI > 25 in males, 38.87%, only 35.47% of female patients are obese. Conclusion The result indicates that there is much higher prevalence of T2DM and BMI than expected. Therefore, may this susceptibility be caused by low birth weight during the Khmer Rouge Famine and the changes of life-style due to the rapid growth of fast food chains?