A large-scale new report warns that medical evidence is stronger than ever that excess body fat increases a person's risk for numerous cancers.
The report by the American Institute for Cancer Research and the World Cancer Research Fund says there is also convincing evidence linking consumption of alcohol, red meat and processed meat to elevated cancer risk.
The report, Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective, was releasedWednesday in Washington. It says carrying excess body fat boosts the risk for cancer of the esophagus, pancreas, colon, kidney and endometrium, as well as breast cancer in post-menopausal women.
Consumers are advised to avoid excess weight gain by limiting intake of high-fat and sugar-rich foods that are low in fibre, including hamburgers, french fries, pastries and sugary drinks.
The report by an expert panel also says there is more convincing evidence than a decade ago linking consumption of red meats like beef, pork and lamb to colorectal cancer.
The panel says consumers should limit intake of cooked red meat to about 500 grams per week.
Ramp up veggies, panel recommends
The experts say bacon, ham, sausage and luncheon meats should be avoided completely, and that every 48 grams of these processed products consumed per day bumps up the risk of colorectal cancer by 21 per cent.
In a separate recommendation, the panel says meals should be planned around non-starchy vegetables and fruits, served with such protein sources as poultry, fish or eggs.
"We are recommending five servings or more of vegetables and fruit daily because, like physical activity, they pack a double whammy against cancer," panel member Dr. Phillip James said in releasing the 517-page report.
"Probable evidence indicates they help reduce cancer risk on their own, and as low energy-dense foods, they help maintain a healthy weight, which the evidence shows has a big influence on cancer risk," James said.
The experts also found convincing evidence that alcohol consumption is linked to cancer of the mouth, pharynx, larynx and esophagus. It is also implicated in colorectal cancer among men and pre- and post-menopausal cancer in women.
Drinking alcohol is a probable cause of liver cancer and colorectal cancer in women, they say.
"It doesn't matter whether you are talking about wine, beer or spirits, when it comes to cancer, even small amounts of alcohol raise your risk," James said. "In light of evidence suggesting that small amounts of alcohol protect against heart disease, however, the panel decided to recommend limiting rather than avoiding consumption."
The report recommends limiting consumption to no more than two drinks a day for men and one drink a day for women.
The report, the second by the expert panel in 10 years, is the most comprehensive ever published on the evidence linking cancer risk to diet, physical activity and weight.
It is the culmination of a five-year process that involved nine independent teams of scientists from around the world, hundreds of peer reviewers and 21 international experts who reviewed and analyzed more than 7,000 large-scale studies.