You've been good; exercising, eating right, doing sit-ups until your abs burn and the spare tire around your middle hasn't budged an inch.

Or maybe you haven't been so good and are looking for an easy way to lose stubborn belly fat.

Either way, there have been some interesting medical studies that have come out over the last year on belly fat. Researchers have discovered some simple, but effective things you can do to get rid of belly fat without buying expensive pills or other weight loss gimmicks and without changing your diet or living at the gym.

Read on to find out three simple changes you can make in your daily life to get rid of up to 50% of your belly fat.

Calcium has been in the news for years as a weight loss aid. Research has found that people who have higher intakes of calcium weigh less than those who don't eat as much calcium. Calcium works by inhibiting fat absorption and, because scientists believe low levels of calcium cause increased appetite, adequate levels reduce hunger.

To effectively use calcium for belly weight loss, take 1200 mg of calcium over the course of a day, preferably before meals. Supplements are ideal because they provide calcium without adding any calories to the diet. Consider taking a Viactiv supplement or a pill such as Citracal before meals.

Without even realizing it you will; naturally eat less, burn more fat, and lose your gut. However, note that calcium will have to be taken on a long term, consistent basis for optimal results.

Read on for some other simple, but effective ways you can lose belly fat.

A study presented at the Experimental Biology Conference in 2009 showed that blueberries can get rid of belly fat. People who ate 1 1/2 cups of blueberries daily lost 12% of their belly fat. Results were seen even in subjects who ate a high fat, high calorie diet.

The active ingredient in blueberries is a compound known as anthocyanin. This compound controls insulin and glucose levels and determines how the body will burn and store energy.

Incorporating blueberries into your diet is simple (assuming you like blueberries). Fresh blueberries can be consumed by the handful, much like potato chips. They can also be frozen and used as a sweet treat to beat summer heat. In addition, blueberries can be blended with a low-glycemic yogurt such as Oikos to make a healthy breakfast smoothie.

The key to using blueberries effectively is to avoid combining them with lots of fat and sugar and to eat them everyday.

If this seems a little daunting or you're concerned you'll end up like Violet in Charlie and the Chocolate Factory, don't worry, we're going to discuss an even better way to lose belly fat next.

A 2009 medical study published in the Journal of Nutrition took two groups of people and put them on the same regimen with one important exception; one group drank green tea, the other did not.

The group that drank the green tea lost up to 44% more belly fat than the control group. Researchers believe it is the epigallocatechin gallate (EGCG) in green tea that is the active ingredients. Science has shown that EGCG increases fat metabolism in the body making it easier to lose weight. In addition, EGCG is more likely to target belly fat over other areas of the body.

Getting rid of belly fat with green tea requires drinking 5 to 8 cups of tea a day. The tea must be warm and plain--no sugar, no milk, no lemon--as adding any other ingredients deactivates the EGCG. 5 to 8 cups of tea a day is a lot of tea, particularly if you are not a tea drinker, but it can be done with some discipline and attention to detail.

In addition, it's important to buy a high quality tea. Loose leaf organic green tea is the best green tea to use for belly fat weight loss. Failing that, bagged organic green tea is another good option. Below, we've listed some teas for you to consider.

Avoid packaged green tea drinks as they often do not contain enough EGCG to be effective. EGCG capsules are also problematic as their quality and EGCG levels are untested.

When drinking green tea, expect to see results within 10 to 15 days so long as the tea is consumed regularly. To accelerate results, combine green tea with other weight loss efforts such as restricting calories and exercising.