Cholesterol is one of those words that can make people nervous. 

For years, we have been told that high cholesterol is something we need to lower. So if you are fasting, you might naturally assume that your cholesterol levels should be dropping, too. 

But the relationship between fasting and cholesterol is more complicated than that. 

Depending on how long you fast and when your blood is tested, some cholesterol numbers may temporarily increase during a fast. 

That doesn’t mean fasting is harmful. It means your body is changing how it handles fat for energy. 

Let’s take a closer look. 

What exactly is cholesterol?

Cholesterol is a waxy, fat-like substance that your body needs in order to function. 

Your liver makes most of the cholesterol in your body. You also get some from food. Cholesterol is used to build cell membranes, make certain hormones, produce bile acids, and support other important body functions.

Because cholesterol does not mix well with blood, it needs to be carried through your bloodstream. It travels in particles called lipoproteins. 

This is where LDL and HDL come in.

LDL and HDL

LDL stands for low-density lipoprotein. HDL stands for high-density lipoprotein. 

LDL and HDL  are not actually different types of cholesterol. They are different particles that transport cholesterol and other fats through the blood. 

A standard lipid panel may measure total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. 

These numbers give us useful information, but they are only part of the larger picture.

What happens to cholesterol when you fast?

When you stop eating, your body has to make a shift. 

After several hours without food, insulin levels begin to fall. Your body then starts relying more on stored energy. 

One major source is body fat. Fat cells release fatty acids, which can be used for energy. The liver can also use some of these fatty acids to make ketones. 

This is one reason why a blood test taken during a fast does not necessarily look exactly like a  blood test taken when you are eating normally. 

And the longer the fast, the more pronounced these metabolic changes can become.

Can fasting actually raise cholesterol?

Surprisingly, yes. 

Research on prolonged fasting has found that cholesterol can temporarily increase, especially during the early part of an extended fast. 

One older human study followed 36 healthy adults during fasts lasting between seven and 21 days. After one week, total cholesterol increased by an average of 25 percent. However, cholesterol later moved back toward baseline as the fast continued. 

The researchers also saw changes when participants began eating again. 

More recent research has found a similar pattern. LDL and total cholesterol can increase during longer fasts, especially during the early stages.

This is important to understand if you have blood work done during or soon after an extended fast. 

Your numbers may look different from your usual levels. 

That does not mean your long-term cholesterol levels have suddenly become worse. Your body is in a very different metabolic state while you are fasting. 

What about intermittent fasting? 

Intermittent Fasting is different. 

Most intermittent fasting involves repeated periods of fasting followed by regular eating, such as a five hour eating window daily, or alternate-day fasting. 

Studies looking at Intermittent Fasting over weeks or months have generally found modest improvements in some lipid measurements. 

A large umbrella review published in 2024 found that Intermittent Fasting was associated with reductions in LDL, total cholesterol, and triglycerides in overweight or obese adults. However, the researchers also stressed that different fasting methods produced different results. 

A more recent review of randomised trials found that the effects on cholesterol vary depending on the fasting strategy. In other words, a 16:8 schedule, alternate-day fasting, or something like a 5:2 approach are all very different metabolic experiences. 

Why might fasting improve cholesterol over time? 

Part of the answer may have less to do with fasting itself and more to do with the metabolic changes that can happen alongside it. 

Fasting can lead to weight loss, and can improve insulin sensitivity and other markers of metabolic health. These changes can affect lipid metabolism. 

What you eat still matters

If fasting is followed by a diet based mostly on highly processed foods, refined carbohydrates, and seed oils, the metabolic benefits may be different from what happens when fasting is combined with a nutrient-dense whole-food diet. 

It may be more accurate to think of fasting as one part of a larger metabolic picture, rather than a magic switch that simply lowers cholesterol. 

Should you worry if your cholesterol changes while fasting?

A change in cholesterol during fasting doesn’t automatically tell you what your long-term cardiovascular risk looks like. 

The timing of the test matters, too, as does the type and duration of fasting. 

There is also a difference between the short-term changes that happen during a fast and the long-term pattern seen over months or years. 

Bottom line

Cholesterol is an important substance that your body needs.

During a longer fast, cholesterol and other blood lipids can temporarily rise as your metabolism shifts toward using stored fat. 

But you shouldn’t judge your entire metabolic health by a single cholesterol number, especially one taken during an unusual metabolic state such as an extended fast.

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Çamli A, Ülker İ, Terzi M, Yağan E, Özbay S, Ulupınar S. Duration-dependent effects of water-only fasting on blood lipids: a systematic review, meta-analysis, and threshold meta-regression. Front Nutr. 2026 Apr 1;13:1772246. doi: 10.3389/fnut.2026.1772246. PMID: 41994097; PMCID: PMC13079636. 

Meng H, Zhu L, Kord-Varkaneh H, O Santos H, Tinsley GM, Fu P. Effects of intermittent fasting and energy-restricted diets on lipid profile: A systematic review and meta-analysis. Nutrition. 2020 Sep;77:110801. doi: 10.1016/j.nut.2020.110801. Epub 2020 Mar 12. PMID: 32428841.

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