Across the country, millions of Americans try to lose weight only to regain what they’ve lost later on. At least one benefit to this cyclical weight loss and weight gain, known as yo-yo dieting, is that people who go through this won’t increase their risk of cancer, according to a study conducted by the American Cancer Society. Published in the American Journal of Epidemiology, the study is the first of its kind to track cancer risk in both men and women who repeatedly lost and regained weight.

"For the millions of Americans struggling to lose weight, the last thing they need to worry about is that if it comes back, they might raise their risk of cancer," said the study’s lead author Dr. Victoria Stevens, a director at the American Cancer Society, in a press release. "This study, to our knowledge the largest and most comprehensive to date on the issue, should be reassuring. Our findings suggest that overweight and obese individuals shouldn't let fears about their ability to maintain weight loss keep them from trying to lose weight in the first place."

Over the course of 17 years, Stevens and her research team followed more than 132,000 men and women between the ages of 50 and 74. They asked each participant how many times in their life they tried to lose at least 10 pounds, and ended up regaining the weight. Overall, 57 percent of women and 43 percent of men admitted to yo-yo dieting. Afterward, researchers analyzed their cycles of weight loss and weight gain, and compared them to their risks of developing 15 specific cancers — they found no link.

The fear that yo-yo dieting could increase cancer risk began when previous animal studies suggested that regained weight led to T cell accumulation, inflammation in fat tissue, and a decrease in the amount of cells that fight toxic compounds, which are all signs of cancer development. It’s already frustrating for people to go through the cycle just to try to lose weight again. But adding on the fear that this process could increase cancer risk makes it far worse, which is why Stevens and her team set out to uncover the truth.

More than one-third of adults in the United States are obese, according to the Centers for Disease Control and Prevention. Although certain cancers are linked to obesity, along with heart disease, stroke, and type 2 diabetes, regaining weight after losing it does not have a caustic effect.

A group of Australian researchers may be able to explain why so many people fall victim to regaining weight. Their 2011 study, published in the New England Journal of Medicine, revealed that when overweight or obese people lost weight, their bodies responded by implementing changes in their hunger hormones.

One of these hormones was leptin, which is produced by fat cells and is responsible for suppressing appetite. When a person loses weight, leptin levels decrease, thus sending signals to the brain that energy stores are low. This causes metabolism to slow down, ultimately triggering hunger. In the study, even after participants gain the weight back a year later, their leptin levels still remained a third lower than before weight loss, meaning they stayed hungry despite losing and gaining weight.

“These mechanisms would be advantageous for a lean person in an environment where food was scarce,” wrote the authors, from the University of Melbourne and La Trobe University. “But in an environment in which energy-dense food is abundant and physical activity is largely unnecessary, the high rate of relapse after weight loss is not surprising.”

This research adds to a better understanding of how the body reacts to gaining and losing weight. While it’s reassuring to know that regaining it won’t lead to cancer, there are still negative health consequences to yo-yo dieting. Hormonal fluctuations within the body often persist and can even become permanent when a person gains back the weight they lost. This is is why fighting the brain’s signals to eat more food is key to keeping weight off for good.

Source: Stevens VL, Jacobs EJ, Patel AV, et al. Weight Cycling and Cancer Incidence in a Large Prospective US Cohort. American Journal of Epidemiology. 2015.

Sumithran P, Predergast LA, and Delbridge E, et al. Long-term Persistence of Hormonal Adaptions to Weight Loss. New England Journal of Medicine . 2015.