Everyone struggling with changing their dietary habits has wondered this very question. In America, processed foods, fast foods, and junk food are the norm. We learn from a very young age that these foods pack a tasty punch, and vegetables... suck.
Taste is often the first hurdle to address when changing your diet. If you've been eating processed foods, fried food, and other “junk” for many years, your brain and taste-buds are likely NOT going to make the switch to broccoli and chicken without putting up a fight.
The simple explanation is that processed foods are actually engineered to be addictive as a business strategy. Meaning, manufacturers need these “foods” to maximally spike dopamine (your brain's novelty and reward neurotransmitter) so that you'll keep coming back for more. Food engineers do this by incorporating the perfect levels of salt, fat, or sugar in the food and providing interesting textures and mouth-feels that enhance the sense of novelty while you're eating these foods.
Humans are naturally hard-wired to seek out salty, fatty, sugary foods, because in nature, these foods tend to have a lot of nutrition. Processed junk food, on the other hand, is generally very low in nutritional value. This is because food engineers want these foods to elicit a craving without ever making you feel full. When foods contain a lot of nutrients, they tend to make you full very quickly.
Another way food engineers design addictive foods is by using simple flours, such as in the case of breads, that break down rapidly into simple sugars. Bread doesn't actually taste like much of anything, but it's one of the most addictive foods on the planet, because it delivers a quick spike in dopamine when you eat it. Also, the simple sugars in breads, pastas, and crackers are quickly swept out of your blood stream by insulin, making you hungry again shortly after eating.
The biggest issue is that the dopamine system that junk food takes advantage of is responsible for our motivation, drive, and happiness. Having this delicate system down-regulated, the way it is when you live on sugar and junk food, puts you at severe risk of depression and other mental disorders. And the fact that you don't feel good without your dopamine hit makes it much harder for you to change your habits.
Processed foods are intelligently-designed food drugs.
Your brain and taste-buds have been hijacked into believing that truly flavorful, healthy foods like broccoli, Brussels sprouts, fruit and fish have no flavor... because they don't provide a dopamine spike.
So what can you do about it?
Commit to 30 days without processed foods or junk.
Seriously, you can undo the damage to both your taste-buds and your brain in as little as 30 days. What happens is the more you eat these dopamine-spiking junk foods, the more of these foods it takes to get the same spike in dopamine. If you were to take a break from the junk, you'll notice that you are more sensitized. It will take much less sugar or junk food to get the same effect, which will make it hard for you to eat the same amounts. If you go 30 days without soda, you'll realize just how overly sweet soda really is. It's the same level of sweetness it was before, but your tongue and brain were both numb to it.
Shop the perimeter and use the “5 or less” ingredients rule.
By shopping around the perimeter of grocery stores, you can avoid most processed and packaged foods. If it's not in your house, you won't eat it.
Another tactic is to start buying foods with less ingredients. Food products with more than 5 ingredients are more likely loaded with additives that have the sole purpose of making you eat more.
Eat new foods often.
The brain loves novelty, so try to incorporate some variety into your diet as you begin to eat better. Don't eat the same foods over and over again. Try vegetables with different textures and expand your cooking methods to keep things creative.
Nourish your body.
This tactic has to do with how you approach eating. Many people have a disordered way of looking at food. They see eating as a way to fill a void, handle stress, or dull their emotions. So junk food becomes a coping mechanism or a crutch.
It takes time to develop a healthy relationship with food, but it has to come from a place of love. It also takes time to undo the mental connections you've made between food and emotions. If you view food as a vehicle for nourishment, you will see eating healthy as a way to love your body and improve your health. Always ask yourself if you're eating for hunger... or for some other reason.