High-Fat Diets Are All The Rage. But Can They Also Be Dangerous?

While diets high in foods rich in fat like meats, cheeses, butter, dairy, and egg yolks are popular, they don't come without some consequences. New research has provided further insight into what happens to the human body when a person eats a fatty meal. Fatty foods can come in many forms ranging from the classic high-fat, unhealthy foods like milkshakes or a burger and fries all the way to adding butter to your morning coffee for the sake of your health. Therefore, it's worth considering what a large amount of dietary fat, especially those that come from animal sources—does to your health.

Researchers at the Medical College of Georgia recently conducted a study1 that fed healthy volunteers two meals on different days. Both meals provided 1,000 calories, but one was high in fat and low in carbohydrate, and the other was the opposite. Four hours after the meal, measures of artery function, red blood cell appearance, and the levels of an enzyme called myeloperoxidase or MPO (which is capable of damaging arteries) were all measured. Only the fatty meal caused negative changes in the arteries, blood levels of MPO to skyrocket, and red blood cells to change shape from round discs to a spiky appearance more likely to clump and clot. The impact of the fatty meal on red blood cells and MPO were new findings, and the authors indicated that "meals enriched in fat may promote destabilization of vulnerable plaques leading to acute myocardial infarction," the medical term for a heart attack.

Researchers in Germany studied2 14 healthy subjects after receiving a meal of palm oil, a tropical oil similar to coconut oil and almost as high in saturated fat. A single meal high in saturated fat reduced insulin sensitivity, an unfavorable result that drove fatty lipids to be stored in the liver. This same finding was seen in a separate study3 of women, and the reduced insulin sensitivity carried over all the way to the next meal, too.

Bacteria contain dangerous components called endotoxins that can be released into the bloodstream and may contribute to diseases like obesity4. In a study5 on healthy volunteers, a single meal high in saturated fat released endotoxins into the bloodstream while meals with vegetable and marine oils did not cause this release. In another study6, a high-fat meal was worse than smoking three cigarettes in prompting the release of high levels of endotoxins into the blood of healthy volunteers. The endotoxins were demonstrated to activate cells that promote hardening of arteries.

The clotting of blood is involved in heart attacks, strokes, and pulmonary embolism. After fatty meals rich in saturated fat, measures of the tendency to clot increased in a study7 on healthy volunteers. In another study8 on the impact of a single fatty meal of different types, measures of blood clotting were also activated.

Just like the new study on red blood cells, other studies have shown artery damage following a single high-fat meal. After consuming a meal rich in saturated fat, measurements9 of arterial health dropped significantly in subjects with type 2 diabetes. Another study on healthy volunteers observed10 that after a single high-fat meal, measures of arterial health and function dropped dramatically for four hours. This was not seen after a low-fat meal. Finally, another study11 compared a high-carbohydrate meal to a high-fat meal in healthy subjects, and blood flow decreased for four hours only in the subjects fed the fatty meal.

In a classic study12 of the impact of fat ingestion in patients with serious heart disease, a single meal rich in butter fat (saturated fat) resulted in EKG changes and angina chest pain in nearly half of the patients in about three hours. The potential for a fatty meal to trigger heart attacks has been discussed in the medical literature13 for many years.

Remember, everything in moderation. Here's how eating a super low-fat diet can mess with your health, too.