New research further supports the link between excess weight and cancer, after finding that gradually gaining weight from the age of 20 to the point of obesity may triple the risk of developing esophageal and stomach cancers in later life.
The study - led by Dr. Jessica Petrick of the National Cancer Institute in Bethesda, MD - was recently published in the British Journal of Cancer.
Overweight and obesity have become major health concerns in the United States. More than 2 in 3 adults and around a third of children and adolescents are considered to be overweight or obese, raising their risk of type 2 diabetes, stroke, heart disease, and some types of cancer.
Some studies have associated excess weight with increased risk of esophageal and stomach cancers.
However, Dr. Petrick and colleagues note that it has been unclear how weight gain throughout a lifetime might influence this risk. The researchers note that because obesity rates are expected to rise, it is important to understand this association.
"This may provide mechanistic insight and inform the time window of when interventions may be successfully implemented to reduce the incidence of these highly lethal cancers," they add.
More than three times greater cancer risk with lifetime weight gain
To investigate the link between lifetime weight gain and esophageal and stomach cancers, the team analyzed the data of 409,796 individuals aged between 50 and 71 who were a part of two studies: the NIH-AARP Diet and Health Study and the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.
At the baseline of each study, the participants reported their current weight and height, as well as their weight and height at the ages of 20 and 50.
During follow-up, 633 participants developed esophageal cancer and 415 developed cancer of the upper stomach.
Compared with subjects who maintained a healthy weight throughout their lifetime, individuals who reported being overweight at the age of 20 were found to be at a 60-80 percent greater risk of developing esophageal and upper stomach cancer in later life.
Furthermore, the team found that participants who gained at least 15-20 kilograms throughout adulthood and were obese by the age of 50 were around
"This study highlights how weight gain over the course of our lives can increase the risk of developing these two cancer types, both of which have extremely poor survival," says Dr. Petrick.
Study 'highlights the importance of a healthy weight throughout life'
The researchers suggest a number of possible mechanisms by which weight gain may raise the risk of esophageal and stomach cancers. For example, Dr. Petrick notes that excess weight may prompt long-term reflex problems and heartburn, which can fuel cancer.
"It can also change the levels of sex hormones, such as estrogen and testosterone, cause levels of insulin to rise, and lead to inflammation, all of which are factors that have been associated with increased cancer risk," she adds.
While additional studies are needed to confirm their findings, the researchers believe that their research further demonstrates the harms of lifetime weight gain.
"This study further highlights the importance of keeping a healthy weight throughout life to reduce the risk of developing these cancers.
Small steps like taking the stairs more often, keeping an eye on portion sizes and switching to sugar-free drinks are simple things we can all do to help keep a healthy weight."
Sarah Williams, health information manager, Cancer Research UK