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Think you know about metabolism? Chances are, your understanding varies greatly from reality. Throw aside the common excuses attached to metabolism and learn how to finally get your under control, once and for all.

How Fast Can Your Metabolism Change?

It's easy to eat poorly for just 5 days in a row. However in just 5 days of eating a high-fat diet, changes in muscle behavior become measurable, and the tiny, small molecules that regulate our genetics as well as our development of insulin resistance begin change.

How Fast Can Your Metabolism Change?

Whether it's holiday time, a stressful week at the office, or a vacation on a remote beach, it's easy to eat differently for just 5 days in a row. If you have a loved one who becomes ill, or maybe you are just craving some fatty foods and you choose to take a week or month off of eating well-it's just too easy to do.

The problem is - while our waistline may not change too much in just 5 days, our bodies' intricate metabolism does. Most of us know how long it takes to gain weight, but most of us probably don't think 5 days is exactly how long it takes to start to ruin your metabolism.

Metabolism Changes Quickly

When you think about ruining your metabolism, thoughts of fatty snack foods, cakes, and high-sugar snacks while sitting on the couch could be conjured up in your mind. Most people feel that they have to gain around 30 pounds or develop a thyroid to condition to really ruin their metabolism. But recent science has demonstrated just how wrong we might be about what it takes to ruin our metabolism.

When you look at all the processes that make up our 'metabolism' your muscle tissue is king. You already know, biceps, triceps, quads and hamstrings - but the heart is a muscle too, and we require muscles to inhale and breathe oxygen. There are digestive muscles in your stomach to contract and digest food, and more muscles to push food along the digestive tract. You need to use a muscle to blink your eyes or your tongue to speak. All of the muscles in your body added together make up the majority of your metabolic rate. That's because the amount of muscle tissue we have directly indicates how many calories we can burn, just at rest.

When something goes wrong with how these muscles metabolize or 'deal with' nutrients - then we are full speed ahead for a whole host of potential metabolism problems. And yet when we begin eating a high-fat diet, this is exactly what happens. And it happens in just 5 short days.

How to Ruin Your Metabolism in Just 5 Days

A study funded by the National Institutes of Health (NIH) and the American Diabetes Association (ADA) looked at college-aged individuals who began consuming high fat meals including sausage biscuits, macaroni and cheese, and extra butter. They kept the participants caloric intake the same, but changed from 30% of their calories coming from fat to 55% of calories coming from fat.

What they found is that after just 5 days of eating a high-fat diet, the molecular changes in muscle behavior became measurable, and the tiny, small molecules that regulate our genetics as well as our development of insulin resistance begin change. Insulin resistance is a metabolic state where we cannot process sugar efficiently inside cells to be burned for energy, and so instead extra glucose gets stored as fat tissue. These scientists were able to measure the molecular changes in how muscle cells begin to change in response to a high-fat diet, and it's not good. Over time, molecular changes like this are highly likely to become more permanent metabolic issues like insulin resistance or metabolic syndrome, or even diabetes.

So it really does take just 5 days to ruin your metabolism. And yet we don't know how long it takes to correct those metabolic issues within muscle yet. Weight gain overall will ruin your metabolism, and so keeping your fat intake at a moderate level by eating foods like olive oil, nuts, seeds, and avocados - all sources of healthy fats-will help ensure you do not ruin your metabolism and can help keep weight gain at bay.


Anderson, A. S., Haynie, K. R., McMillan, R. P., Osterberg, K. L., Boutagy, N. E., Frisard, M. I., Davy, B. M., Davy, K. P. and Hulver, M. W. (2015), Early skeletal muscle adaptations to short-term high-fat diet in humans before changes in insulin sensitivity. Obesity, 23: 720-724. doi: 10.1002/oby.21031

Sarah Asay's Photo
Written By Sarah Asay, RDN. Published on November 10, 2015. Updated on October 22, 2019.


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