What Really Happens to Your Body When You Stop Eating Fast Food

Fast food has its place in life—sharing a pizza with friends can bring joy, for example, regardless of the nutrients it's giving you.

But cutting down or removing fast food from your diet has its benefits, too.

"As much as I love focusing on positives versus negatives, research shows that many chronic diseases are lifestyle-induced and many heart attacks and strokes could be prevented by incorporating healthier lifestyle habits," says Crystal Scott, RD at Top Nutrition Coaching. "With that being said, it is more about food quality and macro/micronutrient composition. Fast food has less fiber, less water and more saturated fats and sodium than whole foods."

Eating more fast food means you're getting less nutrient-dense foods that your body needs, Scott explains. By quitting fast food, you may take in fewer calories and increase your fiber, vitamin and mineral intake because doing so creates space for more vegetables, fruits, whole grains, healthy fats and lean sources of protein in your diet.

Here are the ways quitting fast food can positively impact your health, according to a few experts.

Your Gut Health May Improve

Restricting fast food consumption can improve your digestion because you're making more room for whole foods rich in fiber and probiotics in your diet.

"High-fat and high-sugar fast foods can wreak havoc on the gut by promoting the growth of unhealthy gut bacteria,” says Bianca Tamburello, RD, a dietitian at FRESH Communications.

“Eating more high-fiber foods (such as fruits, vegetables and whole grains) and probiotic-rich foods (like yogurt and sauerkraut) feeds the healthy gut bacteria and promotes proper gut balance,” Tamburello says.

She adds that, because your gut is intrinsically linked to your immunity and mental wellbeing, these areas of your health may be positively affected. We’ll get more into that a little later.

You'll Lower Your Risk of Heart Disease

"When we consume a diet heavy in saturated fat, it raises LDL levels in the blood and blood pressure, which puts you at greater risk of heart disease and stroke," Scott says.

"Eating less sodium, saturated fat and added sugar from fast food can drastically improve your heart health and decrease your risk of heart disease by promoting healthy blood pressure and better cholesterol levels," Tamburello says.

"Replacing highly processed fast foods with whole foods high in fruits, vegetables, whole grains and lean protein can also decrease chronic inflammation, which contributes to better heart health,” she adds.

You'll Likely Have Better Blood Sugar Control

Frequently eating high amounts of added sugar, often found in fast foods, can put you at risk for prediabetes, type 2 diabetes, and metabolic syndrome. Metabolic syndrome happens when you have several health conditions, including high blood pressure, high blood sugar, excess abdominal fat, and high cholesterol or triglycerides, Tamburello explains.

"Metabolic syndrome is dangerous because it increases one's risk of heart attack, stroke and diabetes,” Tamburello says. “Eating less fast food high in calories, saturated fat, sodium, and added sugar can help prevent metabolic syndrome."

"I do not think that fast food alone is the root cause of diabetes, metabolic disorders or even cholesterol and blood pressure,” Scott says, “but a combined effect with decreased activity levels, decreased adequate hydration and a decrease in fiber and vitamins and minerals."

By limiting your added sugar, sodium, and fat intake from fast food — and eating more nutritious, fiber-rich foods in their place — you may be able to better manage your blood sugar levels.

"Eating more healthy unsaturated fats in place of saturated fats from fast food has been shown to prevent insulin resistance, which means better blood sugar control and prevention of diabetes. Naturally, eating less added sugars and refined starches from fast food prevents blood sugar spikes and promotes better blood sugar control, too," Tamburello says.

You Might Lose Weight

"By decreasing fast food and increasing lean proteins, complex carbohydrates full of whole grains and fruits and vegetables and healthy fats, like in avocados, you increase volume foods that are lower in calories, are more nutrient-dense and leave you full and satisfied, preventing overeating and in general promoting a healthier lifestyle,” Scott says.

You May Sleep Better and Have More Energy

Getting more rest might not be something you think of as a benefit of healthier eating but, because these foods are usually heavily processed and are high in added sugar, they can cause your blood sugar levels to spike and then dip low, Tamburello says. This can cause an energy crash and mess with your sleep.

When you incorporate more high-fiber foods, such as whole-wheat bread, fruits and vegetables, into your diet, it can prevent these big spikes and crashes, she says.

Another reason you might see improvements in your sleep and energy levels: Not getting enough sleep is associated with eating more sweets and fast foods, which increases ghrelin, a hormone that promotes hunger, Scott says.

"A low-quality diet high in added sugar and processed foods and low in fruits, vegetables and protein is associated with poor sleeping patterns. If you struggle with sleep, replacing fast food with high-quality, nutrient-dense foods such as fruits, vegetables, whole grains, nuts and seafood, may help you sleep better and stay asleep longer," Tamburello says.

Your Mental Health and Cognition May Improve

Although research in this field is still growing, more recent studies show that your diet can affect your mood and cognition.

A Dietician’s Tip: Embrace the 80-20 Rule

You don't have to give up all of your favorite fast foods to reduce your health risks. Unless you have specific dietary restrictions, you can still enjoy your favorite menu items as part of a balanced lifestyle.

"I think you can have a well-balanced diet without being overly restrictive, by following the 80-20 rule: 80 percent of the time, you're consuming lean proteins, fruits and vegetables and healthy fats, and 20 percent [of the time you're] enjoying other foods like fast food," Scott says.

"By doing that, you can remove yourself from 'food jail,' remove guilt and shame around food, and allow yourself foods in moderation. This builds a really healthy relationship with food and being able to be more mindful when it comes to choices."

The Takeaway

• Cutting back on fast food can dramatically improve gut and heart health, lead to better blood sugar control, support weight loss, and boost energy and sleep quality.
• Reducing ultra-processed fast foods is linked to reduced cognitive decline and may lessen symptoms of depression and anxiety.
• While limiting fast food offers major benefits by making room for nutrient-dense whole foods, completely giving it up isn't necessary for many people; an 80/20 approach can allow for occasional enjoyment within a balanced diet.