BMI of 25 to 29.9 Measure your middle. Evidence suggests that where you carry excess weight is more important than how much you lug around, and belly weight is the most dangerous. A waist that’s more than 35 inches (40 for men) means too much belly fat—a risk factor for heart disease and diabetes. If you’re in the danger zone, try to lose 5 to 10% of your body weight and also shrink your waistline. (Exercise can help.) If your waist is less than 35 inches, your biggest health benefit will come from exercising and maintaining your current weight. BMI below 25 Check your waistline. Slim folks can have too much belly fat, too. If you do, your goal should be regular exercise, not weight loss. More from Prevention: 50 Ways To Lose 10 Pounds