What makes an energy bar good for weight loss? When it's low in calories and sugar, but high in stomach-filling fiber and protein. Eat one between meals or after dinner to beat back cravings for dessert. Look for a bar with as little sugar and as few calories as possible, but with at least 10 grams each of protein and fiber, says Nelson.

Winner: QuestBar Apple Pie has the least sugar of all the bars here, with only 3 grams, yet still boasts a whopping 20 grams of protein and 18 grams of fiber. Better still, it tastes like a chewy apple tart.