Do you find yourself unable to avoid pulling into a fast food drive-in for lunch? Can you barely resist the urge to get a donut with your coffee? Have you stopped keeping chips in the house because you can\u2019t control how many you eat in one sitting? If you can say yes to these questions, you\u2019re not alone. Most of us find junk food and fast food irresistible, even when we know how harmful they are. These foods are carefully crafted by companies to make you want more. Here are five common fast food ingredients that keep you coming back for more: \tFat is a huge player in junk foods, and it\u2019s appealing to us for a very good reason. Fat molecules provide a lot of energy, and it is energy that can be stored in the body for later. Evolutionarily speaking, fat has been important to our survival as a species. Today, however, we eat way too much of it. Researchers have found in animal studies that eating fat produces a pleasure sensation in the brain similar to that of cocaine and heroin. As with drug use, the more fatty foods you eat, the more tolerant you become to the pleasure. You will need more of it to feel the same pleasurable sensation. \tWe are also hardwired to get pleasure from sugar and probably for similar reasons. Sugary foods can provide us with quick and available energy, so we are drawn to sweetness. Studies similar to those conducted with fatty foods show that, like fat, sugar changes our brains and stimulates the pleasure center. Brain scans of animals high on sugar look eerily similar to those of animals using cocaine. \tFat, sugar, and salt make up the trinity of junk and fast food ingredients. Salt is not an energy source, but it is an important nutrient that provides electrolytes. Just like sugar and fat, this mineral stimulates the pleasure center in the brain, releasing chemicals that make us feel good. Animal studies have shown that rats show signs of being addicted when given a high-salt diet. They not only demonstrate brain changes similar to those seen with drug use, but the lab animals also showed signs of being psychologically addicted. \tIf you have ever casually mentioned that you think you are addicted to cheese, you might not be wrong. Casein is a protein found naturally in milk and cheese, but in many cheeses it is concentrated by the manufacturer to make the product tastier. Casein is even sometimes added to French fries and milkshakes. When you digest casein, it breaks down into casomorphins, compounds that are similar to opioid drugs like heroin. This explains why cheesy foods, like macaroni and cheese, are considered comfort foods. The casomorphins relieve pain and produce relaxation. \tMonosodium glutamate, or MSG, has long been a controversial food additive. Experts still can\u2019t agree on whether it is really bad for us. Those who think it is bad believe that it is addictive, but evidence is scarce. MSG used to be common in Chinese takeout food, and many have claimed it made the foods highly addictive. Many restaurants now leave it out due to health concerns, but other junk foods and fast foods still include MSG to improve the flavor. Now that you know your favorite junk foods and fast foods are designed to get you hooked, take a look at your eating habits. Don\u2019t let the food companies win. Cut back on fast food and eat more fresh and whole foods. It will be difficult initially, thanks to the addictive nature of these ingredients, but you can do it.