You may think that you can postpone weight loss because you’re young. But a new study says reducing your body mass index (BMI) from the “obese” range to the “overweight” range before you reach middle age can cut your risk of early death in half.

According to the Centers for Disease Control, if your BMI is 25.0 to under 30, your weight is within the overweight range. If your BMI is 30.0 or higher, you are obese.

As many as 12 percent of early deaths in the U.S. may be related to a person being obese between early adulthood and midlife.

In the U.S. more than 40 percent of the population is obese. Obesity is associated with a number of chronic health conditions such as heart disease, diabetes and some types of cancer. It is also a risk factor for early death.

Researchers at Boston University School of Public Health (BUSPH) studied the weight patterns of over 24,000 adults between 40 and 74 years old using information collected during the 1988-2015 National Health and Nutrition Examination Surveys. Participants’ BMIs were noted at three points in time: at age 25, ten years before they began the study and when they entered the study. Over the course of the study, participants’ changes in BMI were analyzed in relation to the likelihood that a person died over the course of time.

Those who lost enough weight between early and middle adulthood to drop from a BMI in the obese range to being simply overweight had a more than 50 percent reduction in mortality risk relative to participants who remained obese throughout the period. Their risk of death was closer to that of someone who had stayed in the overweight range from age 25 until midlife.

Losing weight later in life, after midlife, did not seem to produce a lower risk of death, but this may be because weight loss later in life is often related to a person’s worsening health.

If everyone whose BMI was in the obese range when they were 25 had been able to lower their BMI to the overweight range by midlife, just over three percent of the people who died in the study would have lived. However, weight loss among the participants was rare overall, and less than one percent of the study group had BMIs that went down.

This study sheds new light on the importance of achieving and maintaining a healthy weight over the course of your life. The researchers believe that as many as 12 percent of early deaths in the U.S. may be related to a person being obese at any time in their life between early adulthood and midlife.

The study was published in JAMA Network Open.