If you've ever decided to start eating healthier but soon found yourself reaching for a bag of chips, it's not just because you lack self-control. You're probably fighting against enemies – trillions of them, in fact – that you can't see.

The bacteria in your gut play a larger role in your life than you may think. They are linked to your brain in what scientists dub "the gut/brain axis," which they use to send signals to your brain, affecting your decisions, especially with regards to what you eat.

If you feed the bacteria in your gut with junk food, you will be supporting the growth of those microorganisms that thrive on junk food. Soon these bacteria will multiply and keep on asking your brain for more – you got it right – junk food. This is how bad cravings are created. (Related: Junk food is engineered to addict you to chemical ingredients.)

The only way to put a stop to the cravings is by doing the opposite and starting to eat healthily. Consuming a diet rich in fruits and vegetables will starve out junk food-loving microorganisms, causing a decline in their numbers and reducing those cravings. The microorganisms that like healthy food will multiply in their place, fostering a healthier microbiome.

It doesn't take much to foster a population of friendly bacteria in your gut.

Fill your diet with fiber-rich food

There are two types of fiber, soluble and insoluble, and both are good for you. Insoluble fiber is usually found in the roughage of food items like vegetables, whole grain cereals, and fruits.

As implied by its name, insoluble fiber cannot be digested by humans. When eaten, it acts as a broom of sorts that transports toxins as it travels through your intestine and exits your body. Soluble fiber, on the other hand, absorbs water and helps in stabilizing digestion.

Apart from all these, fiber can act as a prebiotic, a substance that the human digestive system cannot process, but is eaten by bacteria in the gut instead.

Eat more fermented food

You may not like the smell of kimchi, but it's good for you. Fermented items like sauerkraut, kombucha, kefir, and yogurt help maintain a healthy balance of bacteria in your gut. The fermentation process occurs because of the action of microorganisms, so these items do contain microbes that are good for your digestive system.