In a study, published in the International Journal of Epidemiology, the researchers wanted to find out how adult overweight (BMI over 25) and obesity (BMI over 30) increase the risk of different types of cancer.

The study showed that if you were overweight before age 40, the risk of developing cancer increases by:

• 70 percent for endometrial cancer.
• 58 percent for male renal-cell cancer.
• 29 percent for male colon cancer.
• 15 percent for all obesity-related cancers (both sexes).

"Obesity is an established risk factor for several cancers. In this study, we have focused on the degree, timing and duration of overweight and obesity in relation to cancer risk," says Professor Tone Bjørge, at Department of Global Public Health and Primary Care, University of Bergen.

Obesity increases risk over time

In the study, the researchers included adults with two or more measurements, obtained at least three years apart, and before a possible cancer diagnosis.

On average, the individuals were followed for about 18 years.

Obese participants (BMI over 30) at the first and second health examination had the highest risk of developing obesity-related cancer, compared to participants with normal BMI.

"The risk increased by 64 percent for male participants and 48 percent for females," Bjørge said.

Avoid weight gain

Obesity is a global challenge and associated with increased risk of several types of cancer.

The results from the study show that overweight and obese adults have an increased risk of postmenopausal breast, endometrial, renal-cell and colon cancer.

"Our key message is that preventing weight gain may be an important public health strategy to reduce the cancer risk," added Tone Bjørge.

Key facts

• The researchers used data for 220 000 individuals from the Me-Can study, with participants from Norway, Sweden and Austria.
• Data from health examinations, including information on height and weight, were linked to data from national cancer registries.
• 27 881 individuals were diagnosed with cancer during follow-up, of which 9761 (35 percent) were obesity-related.

Source: The University of Bergen