Q: My New Year’s resolution is to lose weight. Any advice?A: There are many ways to “define” being overweight or obese:The body mass index (BMI) is calculated from someone’s height and weight (see nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm for a BMI calculator). People with a BMI less than 18.5 are considered underweight, 18.6 to 24.9 is a healthy weight, 25 to 29.9 is overweight, over 30 is obese and over 40 is severely obese.