Health experts have urged younger people to try to maintain a healthy weight throughout their lives as stark new figures show that gaining weight over a lifetime can dramatically increase a person's risk of getting certain types of cancer.
People who are overweight in their twenties and become obese in later life could be three times more likely to develop cancer of the food pipe or the upper stomach, the study found.
Researchers at the National Cancer Institute in Bethesda, in the US, analysed data on more than 400,000 people, including information on their height and weight at ages 20, 50 and at the time they gave the information.
These people were then tracked to see whether they developed these cancers in later life.
The reserach, published in the British Journal of Cancer, found that continued increases in excess weight across a lifetime, particularly when exposure begins by early adulthood, is associated with increased risks of both types of cancer.
The strongest links were found among people who reported being overweight in their twenties who progressed to obesity in later life.
Participants in this group had a three times increased risk of oesophageal (food pipe) or upper stomach cancer.
Similarly, people that first reported being overweight at age 20 had 60-to-70% increased risk of developing these cancers, the authors said.
People who gained more than 20kg during adulthood were also twice as likely to develop food pipe cancer.
Study lead Dr Jessica Petrick said: "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.
"Carrying excess weight can trigger long-term reflux problems and heartburn that can lead to cancer.
"It can also change the levels of sex hormones, such as oestrogen 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."
Sarah Williams, health information manager at Cancer Research UK, said: "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."
Figures from Cancer Research UK show that around 5,600 people are diagnosed with oesophagus and upper stomach cancers in England every year.
The charity said that after smoking, being overweight is the biggest preventable cause of cancer in the UK and contributes to around 18,100 cases each year.
Being overweight has already been linked to bowel, breast, liver and pancreatic cancers.