We’ve all been there—there, meaning the drive-thru, with our tummies rumbling. In a weak moment, throwing caution to the pick-up window might not seem like a grave mistake, but the terrible feeling that rises in your gut as soon as you dispose of the last empty ketchup packet is more than just regret.
Science, known for ruining everything, has shown that a single junk food meal can have a huge impact on your body—and not in a good way. Couple that with the fact that the largest study of fast food to date found that the portion sizes, calories, fat, and sodium have increased across the board, and you’ve got trouble.
Take the fast food standby, the hamburger. Even a single quarter-pound patty rings in at an excess of 500 calories, 25 grams of fat (nearly half of those saturated, accounting for more than half of your recommended daily intake, plus some trans fats), 40 grams of carbs, 10 grams of sugar, and 1,000 milligrams of sodium. It easily makes the list of foods nutritionists never eat, so you shouldn’t either.
When that burger hits your bloodstream, which begins roughly 15 minutes after your first bite, you’ll experience a massive surge of glucose as your body converts all those calories to energy. That triggers the release of insulin to offset the spike—sometimes, a bit too much insulin, which leads you to feel hungry again in a few hours. Repeating this pattern can lead to insulin resistance, a precursor to diabetes. Researchers attribute this to oxidative stress on cells that occurs when taking in an excessive number of calories in one sitting.
All that saturated fat also has a pretty instantaneous effect, too. When researchers fed healthy men a fast food meal high in saturated fat and then measured their endothelial function, they found that their arteries were significantly impaired and did not dilate as much. This is the first step to atherosclerosis, the restriction of blood flow that can lead to cardiac disease. Find out more about the effects eating fast food has on your immune system.
The high amounts of sodium in that all-beef patty can compound the problem. A separate study published in the American Journal of Clinical Nutrition found that salty foods can negatively impact blood vessel function in as little as 30 minutes.
And that’s not all. Researchers served study participants a 1,000-calorie meal loaded with saturated fat, and found that within four hours, everyone who consumed it had elevated triglycerides and fatty acids in their blood, as well as impaired arterial function. But less expectedly, the study authors also noted that the test subject’s immune systems had responded to the meal the same way they would have to an infection.
So next time temptation hits and you think about giving in “just this once,” consider that a quarter-pounder is going to give you so much more than indigestion—and that’s without fries and a soda—and keep on driving. Sure enough, that soda has some unpleasant effects on your body, too—find out how just one can affects you.