It's a common scenario: you're eating a healthy diet and exercising regularly but the bathroom scale won't budge. Here's the good news: the problem usually isn't a slow metabolism, genetics or your thyroid. Instead, these five common diet mistakes may be keeping the pounds on.

Blunder 1: Eating "healthy" portions of healthy foods

Sure, grilled salmon is better for you than a juicy, marbled steak. But that doesn't mean you should eat a 10 ounce portion of it. Even though it's packed with heart healthy omega-3 fats, 10 ounces of salmon has 583 calories (the same number of calories found in 10 ounces of sirloin steak). Keep your portion size of cooked meat, poultry and fish to three to six ounces at meals.

And yes, skim milk is a nutritious, fat free beverage but it still has calories. Instead of drinking two 12 ounce glasses with dinner, limit yourself to an 8 ounce serving. Drink water if you're still thirsty. Doing so will save you 165 calories.

Blunder 2: Thinking fruit and vegetables are "free" foods

Produce is one of the best sources of vitamins, minerals and antioxidants. That's why we're told to get seven to 10 servings, combined, each day. Even so, if you want to lose weight you can't eat all the fruit and vegetables you want.

Consider that peas (1/2 cup = 62 calories) and potatoes (1/2 cup = 68 calories) are higher in calories than vegetables that have a higher water content like broccoli (22 calories) and green beans (27 calories). And a medium sized fruit has anywhere from 70 to 100 calories because it's contains natural sugar.

Fill up on low calorie, water-rich vegetables such as leafy greens, zucchini, peppers, broccoli and cauliflower. Aim for four to five servings per day. Keep your fruit intake to three servings per day.

Blunder 3: Going crazy with condiments

That seemingly innocent squirt (or two) of ketchup, brush of barbecue sauce, or slather of peanut butter may not be as harmless as you think -- especially if you use condiments to flavour most of your meals. These add up at often 50 to 100 calories per tablespoon.

Lower calorie alternatives include salsa, hot sauce, mustard, hummus and fat-reduced mayonnaise. When you do use higher calorie condiments, use them wisely. Read nutrition labels to learn calories per serving.

Sugars can sneak in too. Maple syrup on oatmeal, sugar in coffee and honey in tea can add up over the course of a day. Per tablespoon you'll find 52 calories in maple syrup, 64 calories in honey, and 50 calories in sugar. If you can't give up added sugars, cut back. Use only one teaspoon of sweetener on your cereal and in coffee and tea.

Blunder 4: Sprucing up the salad

What starts out low in calories -- lettuce, tomato, cucumber, mushrooms -- can turn into more than a meal if you're not careful. Add-ins like cheese, nuts, avocado, and dried cranberries add flavour but at a cost: plenty of calories. Once you account for the dressing, a small side of greens can pack in as many as 600 calories.

Keep salads simple: stick with leafy greens and vegetables. For main course salads, top with chicken breast, tuna, salmon or beans (e.g. chickpeas, kidney beans, lentils).

Vinaigrette dressings often have fewer calories than creamy ones, but they're still oil-based. And at 120 calories per tablespoon of oil, it's wise to use a measuring spoon to dress your salad.

Blunder 5: Eating like an athlete

It's easy to justify eating a larger portion or an extra dessert because you're working out four days a week. Surely you're burning those calories off. But if you eat more food your weight will hold steady instead of drop.

Another common mistake: overeating protein because your strength training. It is true that exercise increases protein requirements. But most people, athletes included, can get what they need from diet alone. If you're already getting the calories you need -- and I suspect you are if you're not losing weight -- excess protein from a steady intake of protein shakes and protein bars will be tucked away as fat.