Even though (or maybe because) I’m a registered dietitian and associate nutrition editor of EatingWell Magazine, I think that healthy diets should leave room for indulgences. (Small treats won’t break your diet and may even help you stick to an overall healthy eating pattern.) That being said, I think there are plenty of tasty ways to substitute healthier ingredients for higher-calorie foods without feeling like you’re making a big sacrifice taste-wise. Here are some of my favorite swaps. Try them all and you can save 875 calories!
Related: 4 Habits of Skinny People 
Swap: Some of the avocado in guacamole for zucchini
Save: 100 calories
The monounsaturated fats in avocado—the main ingredient in guacamole—may be heart-healthy, but they also pack a calorie punch. A typical avocado-heavy guacamole delivers 200 calories per half cup. For the May/June 2012 issue of EatingWell Magazine, the EatingWell Test Kitchen came up with an amazing (and surprising) substitution for half the avocado—cooked zucchini! This is some of the best guacamole I’ve had—and the swap shaved 100 calories off the real deal. Get the recipe for slimmed-down guacamole and more healthy Mexican dips. 
Swap: A hamburger bun for an English muffin
Save: 120 calories
As grilling season kicks into high gear, beware the burger bun. A typical bun delivers 236 “empty” calories—mostly from white flour—without adding much taste or nutrition. Save 120 calories simply by swapping that burger bun for an English muffin. If you want to really pump up the nutrition, choose a whole-wheat muffin, which will give you added fiber, helping you feel more full from your meal. No English muffins at your friend’s cookout? Scoop out the inside of a regular hamburger bun and you’ll save 60 calories.
Swap: Premium ice cream for blended frozen banana “yogurt”
Save: 170 calories
If you’re really craving ice cream, go for it (sometimes I find that just a spoonful will satisfy me, or measure yourself a half-cup serving and enjoy). But if it’s just a cold, creamy treat you’re after, this skinny swap is surprisingly satisfying: put some slightly thawed frozen bananas in the blender and blend until they’re creamy, the consistency of soft-serve ice cream. Sprinkle in cocoa powder if you want a chocolaty version. A small banana is 90 calories; a half-cup serving of premium ice cream is 260 calories.
Swap: Mayonnaise for low-fat mayo
Save: 45 calories
Mayonnaise—made primarily from oil and eggs—is not surprisingly a calorie bomb (a tablespoon of the stuff packs 90 calories). It may seem like a no-brainer, but swapping low-fat mayo for full-fat is one switch that EatingWell’s Test Kitchen cooks consistently find worth it. Of all the variations on mayo—light, no-fat, reduced-fat—they’ve found that low-fat mayo tastes the best and has only half the calories (just 45 calories per tablespoon).
Swap: Some ground beef for grated vegetables
Save: 30 calories
Ground beef is chock full of healthy iron and zinc, but its saturated fat can lend extra calories (that’s why it’s always good to look for lean ground beef). To sneakily lower calories without sacrificing portion size or flavor, try bulking up your beef with shredded or chopped vegetables—mushrooms, peppers, zucchini and even carrots work well. (You might recognize this trick from all those cookbooks on sneaking vegetables into children’s diets, but it works for adults, too—in fact, it’s another trick the EatingWell Test Kitchen uses often to cut calories, boost vegetables and make recipes healthier.) We recommend adding up to 1 cup of chopped or grated veggies to a pound of ground beef when making meatloaf, chili and other dishes. Doing this may help you stretch that pound of beef from four servings to five—and trim 30 calories per serving.
Swap: Chicken for tofu
Save: 100 calories
You might think of tofu only as a replacement for meat or chicken when you want to eat vegetarian, but when you’re looking to save calories it’s also a great choice. Ounce for ounce, it has fewer calories than chicken or beef, saving you up to 100 calories per 3.5-ounce serving of chicken breast. (Try it yourself in this Tofu Parmigiana and more delicious tofu recipes. )
Swap: Sour cream for plain yogurt
Save: 30 calories
Rich and creamy plain yogurt adds tang and texture similar to sour cream for baked potatoes, burritos or black bean soup. Go for nonfat or lowfat yogurt for the biggest calorie savings (and an added dose of calcium). You’ll save 30 calories per 2 tablespoons.
Swap: Potatoes for cauliflower
Save: 100 calories
There’s a reason cauliflower has a reputation as the skinny “starch.” Boasting only 29 calories per cup (compared to 130 calories in a medium potato), it also delivers almost a day’s worth of vitamin C. It’s a versatile vegetable that’s delicious mashed, blended into a “creamy” soup or roasted. Celery root is another good swap for mashed potatoes—just replace some of the potatoes with boiled celery root.
Recipes to Try: Creamy Mashed Cauliflower and More Easy Cauliflower Recipes 
Swap: Spaghetti for spaghetti squash
Save: 180 calories
When I first discovered spaghetti squash I was thrilled—I baked it and used the spaghetti-like interior as a base for my favorite homemade pasta sauce and instantly doubled the amount of vegetables I ate at that meal. But this swap not only ups your veggie intake, it slashes calories while letting you enjoy the flavors of your favorite noodle dishes. Spaghetti squash has only 42 calories per cup—180 calories less than a cup of cooked spaghetti! If you’re not a fan of spaghetti squash, you can still lighten your pasta by using less pasta and bulking up on veggies in the topping.
Must-Read: 7 Simple Ways to Save 100 Calories 
What sneaky substitutions do you use to save calories? Tell us what you think below.