We all want to battle the belly bulge, but new research points out just how much these bellies have grown in the last 12 years. Before you throw out all of your food, you may want to know, it might not have anything to do with an increase in body mass index. A recent study published in American Journal of Clinical Nutrition, looked into the waist measurements of both men and women who participated in the National Health and Nutrition Examination Survey from 1999 to 2012. After a comparison of both BMI's and waist measurements of each gender, it showed that women's waistlines grew about 1.5 inches during the course of the study (on average) while men's only expanded 0.75 inches. Women under 40 also tended to see the greatest increase in waist size. However, during the same study time frame, men's BMIs increased by 0.7, and women's only went up by 0.6. Although researches are not 100 percent certain as to why women have the larger waist size, it was pointed out that a larger midsection has been associated with various factors like stress, depression, certain medications, lack of sleep, and yo-yo dieting.