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Long associated with serrated spoons and deprivation diets (Joan on Mad Men was a fan), the sour, zingy citrus deserves a spot on your plate. A 2014 lab study at the University of California, Berkeley, found that grapefruit juice not only helped animals lose 18 percent more weight than those that drank just water, but also lowered their blood glucose as effectively as the type 2 diabetes drug metformin. If you have a choice of yellow or pink, go for the later: A ruby-hued grapefruit provides about a fifth of your daily vitamin A needs (critical for vision and skin) and contains lycopene, the pigment that lends tomatoes their potentially heart-protecting properties. One word of caution: Grapefruit can interfere with certain medications, so check with your doctor before adding it to your diet.