What Happens To Your Body If You Eat Only 'Junk Food' For A Week

At one time or another, most of us have given in to the craving for junk food. According to a 2018 report from the Centers for Disease Control and Prevention, nearly 45% of adults aged 20 to 39 consumed fast food on a daily basis. Additionally, a 2021 study published by the Journal of Nutrition showed that 75% of total sugar, 46% of sodium, and 48% of saturated fat in the diets of adults in the United States come from junk food.

However, although salty and sugary snacks and greasy cheeseburgers can be enjoyable indulgences, excessive junk food consumption comes with a number of health risks.  Eating too much junk food can cause obesity, cardiovascular disease, diabetes, and some cancers. Even in the short term, junk food consumption can lead to some issues, including issues with concentration, lethargy, and bowel problems (via Frontiers for Young Minds). This is what can happen to you over the course of a week if you make junk food the staple of your diet. 

Digesting and metabolizing the food you eat takes energy, and the healthier the diet, the more energy is required to process it, leading to more calories burned (via Healthline). However, a high-carb, high-fat meal or snack will be absorbed more slowly by the body, meaning that fewer calories are burned throughout the day. A 2010 study published in Food & Nutrition Research showed that people who ate a cheddar cheese sandwich on whole grain bread burned double the calories via digestion than people who ate the same sandwich made with refined grains and processed cheese. 

It's no secret that junk food has little to no nutritional value, and those low-nutrient snacks pass through your body rapidly, according to experts at Wausau Weight Loss. This means that you get hungry again more quickly, which leads to your craving more junk food, and the cycle repeats itself. It also means that, because of the fast digestion process, your body burns next to no calories processing these snacks. As a result, plenty of calories go in and few go out.  

As most everyone knows by now, junk food is very low in nutritional value. What it is high in, among other things, is sodium, sugar, and saturated fats. And, because much of junk food is made from refined ingredients, it tends to break down very quickly in your system. As a result, your insulin levels spike, while your blood sugar drops, making you feel tired and lethargic. Additionally, a 2016 study published in the Journal of Hypertension showed that consuming high-sodium foods could have a direct effect on the blood vessels. 

Junk food could also have even more serious effects on your central nervous system, impacting your ability to concentrate, as evidenced by a 2020 study published in the Sadara Medical Journal. That study showed that excessive eating of fast food among college students was linked to a lower short-term memory score. Long-term, you could also face more devastating problems. A 2016 study published in Environmental Health Perspectives showed that processed foods are high in phthalates, chemicals that impact hormone function in the body. Too much exposure to phthalates could lead to reproductive problems. A 2020 study published in the International Journal of Environmental Research and Public Health showed that phthalate exposure can lead to fertility problems, alterations in puberty, and cancer in both males and females. 

Junk food can have a number of effects on your brain, ranging from depression to memory problems and irritability (via Bayside Psychotherapy). This is primarily because the food you eat influences your gut bacteria, which then helps to regulate some of your body's mood-affecting hormones, such as serotonin, a hormone known to produce positive feelings. The unhealthy ingredients in snack foods can directly impact the production of serotonin, which can bring your mood down. 

Additionally, as demonstrated by a 2022 study published in Public Health Nutrition, people who subsist on a diet of unhealthy, processed foods are more likely to experience symptoms of anxiety and depression. The study showed that people who ate processed foods had significant increases of depression versus those who did not. They also had a far lower rate of "mentally unhealthy days" than people who did not make these foods a major part of their diets. 

Junk food isn't just bad for your insides; it can also have a negative effect on your outward appearance as well. According to a 2020 study published in JAMA Dermatology, adults who ate a diet high in fatty and sugary foods increased their chances of developing acne by more than 50%. A 2010 study published in the Journal of the European Academy of Dermatology and Venereology showed that eating fried foods increased the risk of acne by 17%. In addition, the high sodium content in these food can lead to high blood pressure, which can weaken your skin and lead to wrinkles forming. Sugar in junk foods can also make your skin age more quickly, affecting your body”s collagen and forming lines and wrinkles.

The main reason that these foods can wreak havoc on your skin is due to the fact that many of the ingredients, such as sugar, have been known to trigger inflammation due to blood sugar spikes (via Penn Highlands Healthcare). When your blood sugar level rises, it causes your body to produce insulin, which, in turn, leads to more production of oil from your glands. Too much oil eventually leads to acne breakouts and skin problems. 

At one time or another, everyone gets a craving for an unhealthy snack, even if we don't indulge that craving. Whether it's a bag of chips or a sleeve of Oreos, cravings for junk food can be hard to ignore. And if we do answer them, we may find that those cravings continue. Consuming vast amounts of junk food triggers the reward center of your brain, releasing the chemical dopamine and almost giving you the sensation of feeling high. According to the Royal Melbourne Institute of Technology, the sensation is so powerful that, in response, the brain creates more dopamine receptors, leading you to crave more junk food, and ultimately requiring even more to get to that same initial euphoric sensation.

There can also be other triggers that may have you reaching for a can of Pringles. According to a 2013 study from the University of California Berkeley, people who were sleep-deprived were more likely to indulge in junk foods than people who had enjoyed a good night's rest. This could be because, according to the researchers, lack of sleep impacts the frontal lobe of the brain, which regulates our decision-making abilities. 

Among the many physical problems caused by junk food is weight gain, which can not only cause a wide array of issues, but also trigger a hormone imbalance. For one thing, sugar and carbs contained in unhealthy foods raise your glucose levels, and the sugar that isn't converted to energy by your cells will instead simply be stored as fat. Additionally, endogenous estrogen, or estrogen that is naturally produced by your body, is key to retaining fat. When you have a higher body weight, your body produces more estrogen, which further retains the fat you have. Excess weight will also lower your testosterone levels, making you feel sluggish and unmotivated and less inclined to lose weight. 

According to experts at North Valley Women's Care, processed foods increase inflammation, which places stress on the body's adrenal glands, thereby throwing off the body's hormones. These chemicals, sweeteners, and additives in these foods that are designed to give them more flavor can also cause issues with your hormones (via MyVita Wellness Institute). These additives have been linked to changes in the body's levels of such hormones as estrogen, cortisol, and insulin. 

Junk food is high in fat and salt, but one thing it's sorely lacking in is fiber, which is what helps food move through your digestive system more easily. Because of its low fiber content, binging on junk food regularly will leave you constipated and bloated from indigestion. Fried foods and foods that are high in fat are difficult to digest, and move through your system slowly, which can lead to more water being taken out of it. The end result is harder stools that are more difficult to pass. 

These unhealthy snacks can also lead to other digestive issues such as irritable bowel syndrome. Fried foods, processed foods, and caffeinated drinks can all affect the digestive system, the intestines, and the colon. A 2019 report published in the British Medical Journal showed that people who consumed a diet made up of up processed foods were more likely to develop irritable bowel syndrome, as well as more serious illnesses like cancer. 

Given all of the devastating effects that junk food can have on your body, it shouldn't be surprising that it can also be detrimental to your cardiovascular system. According to a 2019 study published in the Journal of the American College of Cardiology, consuming a diet that is high in processed foods, red meat, and sugar can trigger inflammation in the body. This inflammation can raise your risk of cardiovascular disease.

Additionally, according to the Cardiovascular Institute of the South, high-fat and high-sugar foods can lead to a buildup of plaque in your arteries, restricting the flow of blood through the body, increasing your risk of a heart attack or stroke. A 2021 study published in Science showed that foods that are high in saturated fat and choline throws off the balance of gut bacteria and produces metabolites that directly contribute to artery-clogging plaque. Choline, a nutrient commonly found in high-fat diets, can cause the gut bacteria to produce a metabolite known as trimethylamine, which is linked to atherosclerosis.  

Eating poorly won't just affect you during the day; with mood swings and digestive issues, it can also impact your night. According to a 2023 study published by Obesity, people who consumed a high-fat, high-sugar diet had the quality of their deep sleep negatively impacted. The sleep patterns that were observed during the study were consistent with conditions such as insomnia. 

Additionally, junk food consumption  has been linked to poor sleep quality in adolescents. In a 2020 study published in eClinicalMedicine, researchers at the University of Queensland found that teenagers who consumed three or more soft drinks daily increased their odds of a poor night's sleep by more than 50%. Male adolescents who consumed fast food more than four times a week also had 55% higher odds of sleep disturbances than males who only ate fast food once per week. For females, the numbers were slightly lower, but their odds were still 49% higher.