FRIDAY, Feb. 15 (HealthDay News) -- The more weight you carry on your body, the greater your odds of developing cancer, British researchers report.

This is true not only of fairly common cancers such as colon and breast, but also of lesser known varieties, including gallbladder. Moreover, the degree of risk differs between men and women and among different ethnic groups, report the authors of a comprehensive new paper appearing in this week's issue of The Lancet.

"This is a profoundly important issue. Obviously, the obesity epidemic is a huge problem itself, and the relationship to cancer is only one of the many adverse health effects of being overweight and obese," said Dr. Michael Thun, head of epidemiological research at the American Cancer Society. "The evidence has been accumulating now for over 10 years. . . This study tries to provide a quantitative measure of how much the relative risk goes up with each increment, basically jumping from one BMI [body-mass index] category to another."

Although extra fat has already been identified by research as a risk factor for several different types of cancer, Thun said, "the problem of obesity is so large and so difficult to solve that there's a very sound reason for ongoing studies of things that have become increasingly well-known, just because it helps the momentum in stimulating approaches that will actually help people maintain a healthy weight."

Last year, a report issued by the American Institute of Cancer Research and the U.K.-based World Cancer Research Fund concluded that body fat is associated with an increased risk for several different types of cancer including esophageal adenocarcinoma, as well as cancers of the pancreas, colon and rectum, breast (postmenopausal), endometrium and kidney.

Although that report was one of the most comprehensive to date, it did leave some questions unanswered. For instance, are there associations between less common cancers and body weight, and do the associations differ between the sexes and people of different ethnic backgrounds?

The issue is a pressing one, with about two-thirds of adult men and women in the United States overweight or obese. That number is only expected to increase as people continue to eat more and exercise less.

This study, from scientists at the University of Manchester, analyzed 141 articles involving 282,137 cancer cases and 20 different types of malignancies to determine the cancer risk associated with a 5 kilogram-per-meter-squared increase in BMI, roughly the increase that would bump a person from middle-normal weight into overweight.

In men, such an increase in BMI raised the risk of esophageal adenocarcinoma by 52 percent, thyroid cancer by 33 percent, and colon and kidney cancer by 24 percent each.

In women, the same increase in BMI increased the risk of endometrial and gallbladder cancer by 59 percent each, esophageal adenocarcinoma by 51 percent, and kidney cancer by 34 percent.

In men, there were weaker associations between increased BMI and rectal cancer and melanoma. In women, there were weaker associations between increased BMI and postmenopausal breast, pancreatic, thyroid and colon cancers.

In both genders, there were associations between increased BMI and leukemia, multiple myeloma and non-Hodgkin's lymphoma.

For colon cancer, the associations were stronger in men than in women (24 percent vs. 9 percent).

There were stronger associations in Asia-Pacific populations between greater BMI and both premenopausal and postmenopausal breast cancers.

Although the main message is still to maintain a healthy weight, this research might indicate earlier screening for certain cancers, said Dr. Greg Cooper, interim chief of the gastroenterology division at Ireland Cancer Center of University Hospitals and Case Comprehensive Cancer Center in Cleveland. "If someone is obese, then lower the threshold for screening," he said. "One of the cancers they identified is esophageal adenocarcinoma, which is not as common as colon cancer, but it is increasing in incidence. It is thought to be related to reflux, so as a gastroenterologist, if I have a patient who has reflux and is obese, I might lower the threshold for doing an endoscopy. For other cancers like colon cancer, those guidelines are pretty well-established, and this probably wouldn't change practice."

Experts aren't sure why extra fat can lead to malignancies, but changes in the circulating levels of various hormones (insulin, insulin-like growth factors and sex steroids) might explain the link.

Here's more bad news as the world heads for a smoke-free future: An accompanying commentary from Swedish researchers notes that as people quit smoking (the biggest cause of cancer in developed countries), weight gain may become the main lifestyle factor contributing to new cancers.

More information

Visit the American Cancer Society   for more on the different types of cancer.

MONDAY, Feb. 11 (HealthDay News) -- Few people with high blood pressure follow recommended dietary guidelines that help control the disease, a new study says.

In fact, people with hypertension actually appear to be eating worse than before the government-approved guidelines were introduced, according to the report published in the Feb. 11 issue of the Archives of Internal Medicine. The study said young people, blacks and the obese fared the worst in their dietary habits.

A diet high in fruits, vegetables and low-fat dairy products has been shown to help significantly lower blood pressure, according to background information in the article. This Dietary Approaches to Stop Hypertension (DASH) method, first published in 1997, complements other lifestyle changes, such as reducing sodium and losing weight, and can also help lower cholesterol levels, previous studies have shown.

The DASH diet is recommended by the Joint National Committee on Prevention, Detection and Treatment of High Blood Pressure for all patients with hypertension.

The study analyzed dietary, health and personal data of adults collected in surveys done by the U.S. Centers for Disease Control and Prevention from 1988 to 1994 and from 1999 to 2004. Using the DASH guidelines, researchers identified goals for eight target nutrients and calculated scores ranging from zero to nine for individuals with and without hypertension from the surveys; those who scored a 4.5 or higher were considered to be following the diet.

Dr. Philip B. Mellen, of the Hattiesburg Clinic in Hattiesburg, Miss., and his colleagues found that among individuals surveyed from 1999 to 2004, 28 percent had been diagnosed with hypertension. These individuals had an average DASH score of 2.92 (compared with 3.12 among those without high blood pressure), and only 19.4 percent followed the diet. Compared with those surveyed in 1988 to 1994, 7.3 percent fewer individuals with hypertension followed the DASH diet, reflecting fewer patients who consumed target levels of total fat, fiber and magnesium.

The findings suggest that the diet of Americans with hypertension has not been greatly influenced by the recommendations emerging from the DASH trial and instead reflect secular trends in the dietary patterns of the overall population, the authors wrote. Moreover, the DASH score was lower in subgroups likely to receive the greatest benefit from the DASH diet -- blacks and obese individuals.

More information

The National Heart, Lung, and Blood Institute has more about high blood pressure and how to control it.

THURSDAY, Feb. 7 (HealthDay News) -- A diet low in carbohydrates but high in animal fat and protein doesn't seem to increase the risk of type 2 diabetes in women, a new study claims.

"One study is never enough to change a recommendation, but this study is interesting in that it shows that a low-fat diet is no better than a low-carbohydrate diet in preventing type 2 diabetes," said Thomas Halton, lead author of a study in the current issue of the American Journal of Clinical Nutrition. "The one diet that did seem to show a protective effect was a vegetable-based, low-carb diet which consisted of higher amounts of vegetable fat and vegetable protein, and lower amounts of carbohydrate."

The findings, Halton added, were a bit surprising in that most doctors and nutritionists recommend a low-fat diet to prevent type 2 diabetes. "This study showed that a low-fat diet didn't really prevent type 2 diabetes in our cohort when compared to a low-carb diet. I was also surprised that total carbohydrate consumption was associated with type 2 diabetes, and that the relative risk for the glycemic load was so high."

Halton is a recent graduate of the Harvard School of Public Health and has founded his own nutrition consulting company, Fitness Plus, in Boston.

Type 2 diabetes, which is associated with overweight and obesity, is a pressing health problem around the world. In the United States, two-thirds of adults weigh more than they should.

And, according to background information in the study, some 45 percent of women and 30 percent of men in the United States are trying to lose weight at any one time.

While low-fat, high-carb diets are often recommended, the long-term effects of such a regimen are not known.

People who reduce their carb intake generally take in more total and saturated fat and less whole grains, cereal fiber, fruit and vegetables, which can heighten the risk of type 2 diabetes.

For this study, Halton and his colleagues examined the association between low-carb diets and the risk of diabetes among 85,059 women participating in the Nurse's Health Study. The data included 20 years of follow-up.

Women were ranked according to what they ate. "We calculated a low-carbohydrate diet score based on the women's percent consumption of fat, protein and carbohydrate," Halton explained. "A higher score reflected a higher intake of fat and protein and a lower intake of carbohydrate. Therefore, the higher a woman's score, the more closely she followed a low carb-diet, and the lower her score, the more closely she followed a low-fat diet."

Women with a higher score did not have a heightened risk of diabetes. In fact, they seemed to have a small decreased risk when they derived their fat and protein from vegetable rather than animal sources.

Such a low-carb diet is similar to a healthy Atkins diet, meaning one which does not include large amounts of animal fat and animal protein, Halton said.

"When focusing on vegetable sources of fat and protein, this version of Atkins is similar to a low-glycemic Mediterranean diet," he said.

How easy will it be for people to follow such a diet?

"It's probably a very good thing to do . . . [but] people don't understand how to eat well. People don't know what simple and complex carbohydrates are and what it takes to have a good, balanced diet. People go to extremes," said Dr. Stuart Weiss, a clinical assistant professor of medicine at New York University School of Medicine in New York City. "In general, carbs should be limited just like saturated fat needs to be limited. . . If you eat too much of anything, you're bound to get into trouble."

More information

Learn more about healthy eating at the American Dietetic Association  .

FRIDAY, Jan. 18 (HealthDay News) -- Pregnant women who eat a Mediterranean diet rich in fish, fresh fruits and vegetables, legumes, nuts, dairy products and olive oil may help protect their children against asthma and allergies, new research suggests.

The study, published online this week in Thorax, included 468 mother and child pairs that were followed from pregnancy up to 6.5 years after birth. The researchers collected information on eating habits and on the children's asthma and allergy symptoms.

About 36 percent of the mothers ate a low-quality Mediterranean diet during pregnancy, while the rest ate a high-quality Mediterranean diet. A little more than 13 percent of all the children had persistent wheezing, 17 percent had positive responses to skin test allergens, and almost 6 percent had asthma-like symptoms plus positive skin test results.

The study found that mothers who ate a high-quality Mediterranean diet during pregnancy were significantly more likely to have children free of asthmatic symptoms and allergies than women who ate a low-quality Mediterranean diet.

Pregnant women who ate vegetables more than eight times a week, fish more than three times a week, and legumes more than once a week seemed to protect their children the most from asthma and allergies. Mothers who ate red meat more than three to four times a week seemed to increase their children's risk.

Children's eating habits at the age of 6.5 years seemed to have little effect on their asthma or allergy risk, the study found.

More information

The American Academy of Allergy, Asthma & Immunology has more about prevention of allergies and asthma in children  .