Beans!

People who eat beans have healthier diets overall, lower body weight, and a reduced risk for obesity. A study found bean-consumers between the ages of 12-19 weighed 7 lbs (~3 kg) less and had nearly an inch (~2.5 cm) smaller waist circumference than their non-bean consuming peers. Those who ate beans frequently had a 22% reduced risk of being obese.
The Experimental Biology Conference, 2006