During the holidays family, drinks, and good food often interfere with the amount of time people go to the gym. While it's human to take a break, you could be doing more harm to your body than you think. 

Taking just one week off from the gym can cause a person to lose up to 50 percent of their fitness gains, Pete Magill, six-time masters national cross-country champion and author of Build Your Running Body: A Total-Body Fitness Plan for All Distance Runners, from Milers to Ultramarathoners-Run Farther, Faster, and Injury-Free, told Shape. 

The speedy decline in the body's strength and endurance after only seven days without stepping foot in the gym begins with less blood being available for your heart to pump, followed by the decrease of the volume of mitochondria in your muscles, reported Shape. 

"When we exercise, we stimulate the synthesis of proteins, like mitochondria and enzymes, to meet the demand we place on our bodies. When we stop exercising, we eliminate the demand, so we start to lose our supply," Jason Karp, Ph.D., exercise physiologist and author of Running for Women, explained to Shape.    

When you stop exercising for a week your nervous system stops using the pathways formerly used to control muscle contractions, whcih causes muscle weakness; and it causes the enzymes that control your metabolism to decline, reported Shape. 

How fast the body deteriorates also depends on weather you spend more time doing aerobic training or weights and how long you have been physically fit. 

Those who focus more on cardiovascular training are more likely to lose their progress than those who mostly lift weights, reported Huffington Post. 

Cardio exercise is measured by VO2 max - which measures the oxygen that you take in compared to how much actually gets used. VO2 max declines more quickly when a cardio trainer takes off, as compared to a weight trainer, because less blood volume is being pushed around, reported Huffington Post.