3 zero-calorie foods that could keep you from losing weight

Everyone wants to slip into their summer swimsuit and feel great, and it's not too late. When it comes to shedding a few pounds, making small changes can have big results.  But there are a few hidden pitfalls that aren't as obvious as that chilly pint of ice cream lurking in the freezer.

It's never fun to fight the battle of the bulge when you have "unknown forces" against you, but I'm here to shed some light on three "zero-calorie" foods that could be keeping you from shedding those last five pesky pounds.

1. Cooking spray

Non-stick cooking spray is a great way to cut back on calories that you normally consume when cooking with oil. Cooking spray used in excess can rack up the calories as well.

Here's why: Cooking spray, per serving, has a negligible amount of calories. So food companies are permitted to list a serving as "zero calories" on their nutrition labels.  But most people don't use only "one serving" when they spray (1/8 of a second), so go easy on the trigger if you use cooking spray often.

2. Diet sodas

Diet sodas might seem like a sweet tasting, zero-calorie way to address your sweet tooth, but artificial sweeteners "can increase appetite because as the sweet taste hits the mouth, a message is passed on to the body that carbohydrates are coming in.

Then the pancreas swings into action and sends insulin into the bloodstream," according to Annemarie Colbin, a noted expert on healthy eating.

We all know that tightly controlling insulin or blood sugar levels is the best way to keep hunger at bay and also burn calories more effective.  If you're hooked on the bubble stuff and have a hard time switching to just plain water, try replacing diet sodas with sodium-free sparkling water flavored with fresh lemon or lime zest.  Zero-calorie extracts, like mint, orange, and vanilla are another way to perk up your water without relying on artificial sweeteners.

3. Coffee

I love a steamy hot cup of joe in the morning, like many Americans.  Contrary to what most people think about coffee, there's been some compelling health news on antioxidants and coffee.

On the other hand, if you're overdoing it with coffee in hopes of curbing your appetite, it can sabotage your weight loss efforts for two reasons:

Drinking to much coffee can interrupt your sleep patterns.  If you're not getting a restful, full night's sleep, your hunger can dramatically increase as sleep depravation can offset your blood sugar.  If you suffer from sleepless nights suddenly, try stopping all caffeine intake 10 hours before you hit the sheets.

Excessive caffeine intake can also affect your adrenal glands which secrete and manage a number of stress hormones.  If your adrenals are working too hard (because you are activating them with too much caffeine), they can become fatigued – meaning a serious energy lag that can put a damper on your workout and having you earning for sweets for an energy boost that will add in just another crash.

So if you're looking for an easy way to curb appetite, try eating slowing and chewing your food more carefully.  Harvard researchers say feeling full is a combination of the brain receiving a series of signals from digestive hormones secreted by the gastrointestinal tract and signals that come from a nerve located in your stomach.