Obesity 
An estimated 36% of adults and 17% of children and adolescents in the United States are obese. Obesity is a serious health problem that has physical and psychosocial consequences. It increases health care costs to employers and reduces productivity. Rates of obesity in the United States and throughout the world have increased dramatically over the past 40 years and continue to rise in many countries. 
BMI values for adults are interpreted based on a fixed number, regardless of age or sex, using the following guidelines: 
Underweight:   BMI less than 18.5Overweight:   BMI of 25.0 to 29.9Obese:   BMI of 30.0 or more
100 million adult americans are overweight and risk serious disease Causes of obesity 
Overeating and a sedentary lifestyle Hormonal disorders such as hypothyroidism (rare) Corticosteroid drugs Psychological problems  
Are there complications? 
Increased risk of various chronic health problems such as high blood pressure levels Greater risk of gallstones Greater risk of developing diabetes Strains on the joints (osteoarthritis is common in obese people) Sleep apnea (a respiratory disorder)  
BMI and risk of Coronary Heart Disease (CHD) in men 
In a study of British men, CHD incidence increased at BMIs above 22 An increase in one BMI unit is associated with a 10 percent increase in the rate of coronary events Similar relationships have been shown in U.S. populations  
Other overweight/obesity-related health complications 
Cancer 
Twice as many women with a body mass index (BMI) greater than 29 had colon cancer as women with a BMI less than 21 A gain of more than 20 pounds, from age 18 to 40, doubles a woman's risk of postmenopausal breast cancer The risk of endometrial cancer is three times higher among women with a BMI of 30 or higher, compared to normal weight women  
Diabetes 
Twenty-seven percent of new cases of diabetes are attributable to weight gain of 11 pounds or more in adulthood The relative risk of diabetes increases by about 25 percent for each additional unit of BMI over 22 Diabetes is associated with long-term complications that affect almost every major part of the body; it can cause blindness, heart disease, stroke, kidney failure, nerve damage and sometimes requires amputation(s)  
Osteoarthritis 
In a study of middle-aged women, every 2.2 pound increase in weight was associated with a 9.13 percent increase in the risk of developing osteoarthritis in the knees A drop in BMI of two units or more during a 10-year period decreased the odds for developing knee osteoarthritis by more than 50 percent The risk of endometrial cancer is three times higher among women with a BMI of 30 or higher, compared to normal weight women