Hazelnuts are high in fiber, with three grams per ounce. Fiber helps keep you full by slowing down food digestion and absorbing water in the stomach, which tricks your body into believing you've eaten more than you have. Copper, a key mineral for producing red blood cells and maintaining healthy bones and nerves, is abundant in hazelnuts. You can eat them whole as you would any other nut, but don't buy them blanched or peeled – the light-brown skin that covers hazelnuts contains the most antioxidants. 

How to eat them: Make your own Nutella by grinding 1 cup roasted hazelnuts in a food processor until a paste forms, about 5 minutes. Add 1/4 cup cocoa powder, 1/4 cup honey, 1 tbsp olive oil, 1 tbsp vanilla extract, and 1/4 tsp salt; blend 1 minute. Spread on toast, or use to top ice cream.