When we take anything - a supplement, a vitamin, a prescription drug - we should know how it will interact with other things we might take. A key detail to pay attention to is how long something will stay in our bodies.

Fat burners rely on a number of different ingredients to achieve effectiveness. Depending on the specific ingredients used in your chosen supplement, the ingredients may stay in your system only a few hours, or up to several days.

The most important indicator of whether something will stay in your system is whether it is fat soluble or water soluble.

Fat Soluble

Certain vitamins, minerals, and other nutrients, are fat soluble. This means that they are broken down and absorbed by fat cells in our digestive tracts. Before we go further, we should mention that not all fats are created equally.

For instance, some fats are the necessary cell walls of our body's smallest structuress (like phospholipids). Without these fats we couldn’t live. Other fats are needed to regulate our electrical impulses or our body heat. Again, vitally important.

So having things that are fat soluble isn’t a bad thing. It’s only important to know that if something is absorbed and stored into fat, it will stay in our systems far longer. A quick list of common fat burner ingredients that are also fat soluble are:

  • Caffeine
  • Cayenne Pepper
  • Vitamins A, E, and K
  • Chromium
  • Choline
  • L-Tyrosine

It’s not necessarily a bad thing to have these ingredients in your body, but it is important to know that because they are fat-soluble, they may take longer to pass through our systems.

Water soluble

Water soluble compounds dissolve in the water in our digestive tract, and are much more likely to pass through our systems very quickly. That’s one reason why taking a 1,500 mg Vitamin C tablet isn’t always effective. Vitamin C is water soluble, so you’re likely to simply pass all of it on your next trip to the rest room.

Some common fat burner ingredients that are water soluble include:

Being water soluble can actually be a bad thing. It means your body may have a harder time absorbing it. That’s why it’s important to look for the ingredient Bioperine or other black pepper extract in your supplements. Bioperine helps the body more effectively absorb all nutrients for more even digestion.

Also, you may have noted that some things appear on both fat and water soluble lists. This is because not all compounds can be neatly separated by human terminology. Sometimes a given nutrient, like caffeine, will be absorbed by both fatty tissue and water. In cases like Choline, this is a vital versatility of the substance, aiding our body in getting it to all the areas it may be necessary.


How long a nutrient stays in our bodies is in large part a function of whether it is fat or water soluble. Then it comes down to individual biochemistry, and how quickly or slowly our own bodies process or breakdown nutrients stored in the two media.

If you’re concerned with a given compound staying too long in your system and possibly interacting with other medications or supplements, consult your doctor. And when in doubt, don’t take a supplement. Instead, check the market for other products without the ingredient you’re worried about. We have a great list of fat burners here.

About the Author

Steven has been into health, nutrition, and fitness for over 10 years, and has a degree in Physical Education and Coaching. He is an expert in supplements and is devoted to helping his clients achieve their fitness goals and live their best lives.

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