Grapefruit
Grapefruit is low in calories, high in enzymes and can keep you full. In a study published in the Journal of
 Medicinal Food, researchers found that eating half of a fresh grapefruit before meals was associated with significant
 weight loss among obese study participants. Researchers also noted that participants who consumed grapefruit before
 a meal also experienced a significant reduction in two-hour post-glucose insulin levels.