A fat-burning superfood, grapefruit contains a compound that can lower the fat-storage hormone insulin, which in turn can lead to weight loss. In fact, eating half a grapefruit before each meal could help you lose up to a pound a week—even if you don't change anything else about your diet. Because grapefruits are 90% water, which fills you up, they also act as a natural appetite suppressant.
This dark, leafy green has a long list of benefits: it's a rich source of iron, folic acid, vitamin K, vitamin C, lutein, and powerful antioxidants that can help fight diseases like ovarian and breast cancer. Spinach is also loaded with magnesium, which can lower blood sugar and insulin levels (aiding your body in weight loss as a result), according to a 2013 study.
For a 2,000-calorie daily diet, aim for 2½ cups of vegetables and 2 cups of fruit a day. If you consume more calories, aim for more produce; if you consume fewer calories, you can eat less. Include green, orange, red, blue/purple, and yellow vegetables and fruits. In addition to the fiber, the nutrients and phytochemicals in these foods may help protect against certain types of cancer and other diseases. Legumes, rich in fiber, can count as vegetables (though they have more calories than most vegetables). For more fiber, choose whole fruits over juice.