Fats vs. Carbohydrates: Which Are More Important to Reduce Triglycerides?

by William Davis, M.D. Health Professional

In our last discussion (What foods increase triglycerides?), we talked about how fats increase triglyceride levels after eating, but carbohydrates increase triglycerides when not eating (i.e., fasting).

So should you avoid both fats and carbohydrates?

No, of course not. After all, we've got to eat something. Humans cannot survive on a diet of pure protein without fats or carbohydrates. So let's ask: Which is more important in determining your level of triglycerides, fats or carbohydrates?

Without question, carbohydrates are the dominant determinant of triglyceride levels.

Because dietary fats are triglycerides, fats increase triglycerides just after eating in the process of absorption, an effect that lasts several hours after a meal. Triglyceride levels then drop. Curiously, over time, a diet rich in fats reduces fasting levels of triglycerides when you're not actively digesting them.

Unlike fats, carbohydrates do not increase triglycerides in the period immediately following a meal. But carbohydrates stimulate insulin, which leads over time to abdominal (visceral) obesity. The stage is then set for insulin resistance, a situation in which your body no longer responds to its own insulin. This is followed by reduced activity of the enzyme, lipoprotein lipase, the enzyme responsible for metabolizing triglycerides. Even worse, a process called de novo lipogenesis begins, allowing rapid and dramatic conversion of dietary carbohydrates to triglycerides, flooding the blood even more with triglycerides. Both processes cause triglycerides to accumulate, showing up as high triglycerides on your standard cholesterol panel.

Depending on the quantity of fat consumed and other factors, triglyceride levels can reach around 300 mg/dl after a fat-containing meal, only to descend rapidly. In contrast, carbohydrates can increase triglyceride levels many times higher, increasing levels to 300, 400, 500 mg/dl or more, even occasionally in the thousands, after many weeks to months of carbohydrate-excess. But carbohydrate excess leads not just to after-eating high triglycerides, but high triglycerides all the time.

If triglycerides are high all the time, a domino effect of undesirable changes occur: Blood sugar is higher, insulin responses are further blocked, arteries become more rigid, HDL cholesterol drops, small LDL particles develop. In short, heart disease is more likely to develop.

So, in the debate over whether fats or carbohydrates are worse culprits in the American diet, from a triglyceride perspective, carbohydrates are far worse.

William Davis, M.D.
Meet Our Writer
William Davis, M.D.

William R. Davis is a Milwaukee-based American cardiologist and author. He wrote for HealthCentral as a health professional for Heart Health and High Cholesterol.