The worldwide incidence for obesity is increasing. Apart from being associated with increased risks of developing diabetes mellitus, ischaemic heart disease, back problems and joint diseases, obesity is also a risk factor for the development of cancer.

A study from the University of Texas M D Anderson Cancer Center compared 841 patients with pancreatic adenocarcinoma with 754 healthy individuals to see if there is an association between obesity and increased risk of pancreatic cancer (JAMA 2009; 301: 2553 – 2562). Overweight individuals (BMI 25 – 29.9), aged 14 to 39 years, and obese individuals (BMI ≥ 30), aged 20 to 49 years, respectively had a 67% and 158% increased risk of pancreatic cancer. The association was stronger in men than in women. Those who were overweight or obese from the ages of 20 to 49 years had an earlier onset of pancreatic cancer by 2 – 6 years. When non-obese individuals with pancreatic cancer were compared to obese individuals with pancreatic cancer, aged 30 to 79 years, the non-obese individuals had longer overall survival irrespective of the cancer disease stage and tumour resection status.

Once you have become overweight or obese, would losing weight reverse the increased risk of cancer? The Swedish Obese Subjects (SOS) study recently published its study involving 2010 obese patients (BMI ≥ 34 in men and ≥ 38 in women) who underwent weight reduction surgery (bariatric surgery) and 2037 contemporaneously matched obese controls (Lancet Oncol 2009; 10: 653 – 662). The median follow-up time was 10.9 years. Over 10 years, bariatric surgery led to a sustained weight reduction of 19.9 kg while in controls there was a weight gain of 1.3 kg. The risk of developing cancer was reduced by 33% in those who underwent bariatric surgery. However, the risk reduction by bariatric surgery was only seen in women but not in men.

These two studies demonstrate that being overweight or obese will increase your risk of developing cancer. While surgery to help you lose weight can reduce your risk of developing cancer, the goal in life surely is not to become overweight or obese in the first place.

Watch your weight. Keep fit and keep trim.

The World Cancer Research Fund (WCRF) and its sister organization, the American Institute for Cancer Research (AICR) in their recent report titled ‘Policy and Action for Cancer Prevention’ stated that approximately one third of common adult cancers in the US may be preventable. (This is not including those which can be prevented by not smoking.) The WCRF and AICR estimated that eating a nutritious diet, being physically active and keeping body fat under control may prevent:

• 38% of breast cancers
• 45% of colorectal cancers
• 36% of lung cancers
• 39% of pancreatic cancers
• 47% of stomach cancers
• 69% of esophageal cancers
• 63% of cancers of the mouth, pharynx, or larynx
• 70% of endometrial cancers
• 24% of kidney cancers
• 21% of gallbladder cancers
• 15% of liver cancers
• 11% of prostate cancers

According to the report, diet, physical activity and limited body fat could prevent 34% of these 12 cancers overall and 24% of all cancers.

A study from the Karolinska Institute followed 45,920 Swedish male conscripts from the period 1969 - 70 for 38 years and examined the effects of overweight in adolescence on subsequent adult mortality (BMJ 2009; 338: b496). Compared with normal weight [body mass index (BMI) 18.5 – 24.9 kg/sq.m] men, the mortality risk in overweight (BMI 25 – 29.9) and obese (BMI ≥ 30) men was increased by 33% and 114%, respectively. The risk was not increased in underweight men, but in those who were extremely underweight, BMI < 17, the risk of mortality was increased by 33%. The risk of mortality in light (1 – 10 cigarettes / day) and heavy (> 10 / day) smokers was also increased by 54% and 111%, respectively, when compared to non-smokers. (Since the start of this study the number of overweight adolescent men in Sweden has tripled and the number of those who are obese has increased 5 fold. Fortunately, the number of smokers has halved.)

Another study looked at the effects of alcohol consumption on the incidence of cancer risk in 1,280,296 women involved in The Million Women Study (J Natl Cancer Inst 2009; 101: 296 – 305). They attended breast cancer screening clinics in the United Kingdom from 1996 to 2001. The average follow-up time was 7.2 years. The 5 categories of alcohol intake were 0 (24%), up to 2 (29%), 3 – 6 (23%), 7 to 14 (19%) and at least 15 (5%) drinks of 10 g of alcohol (= 1 unit) / week. Increasing alcohol intake was associated with an increased risk of specific cancers. The excess cancer incidence of these cancers, up to 75 years of age, with 10 g increase in daily alcohol intake were:

• Oral cavity and pharynx – 1 per 1000
• Oesophagus – 0.7 per 1000
• Larynx – 0.7 per 1000
• Rectum – 1 per 1000
• Liver – 0.7 per 1000
• Breast – 11 per 1000

To put it another way, the researchers estimated that the background incidence of cancers among women in developed countries was 118 cancers diagnosed per 1000 women up to the age of 75 years. Drinking 1 unit per day increased this by an extra 15 cancers per 1000 women and 2 drinks a day  increased this an extra 30 cancers per 1000 women; the majority of the cancers would be breast cancer.

Most cancers are not inherited. For the small proportion of inherited cancers, your cancer risk is not within your control. For most of us, how you lead your life can impact on your cancer risk. Leading a healthy lifestyle does not reduce your cancer risk to zero; it does however reduce your odds of developing cancer. Do not think that regular health checks will save you from cancers. You hope that the checks will help you detect the cancer at an earlier stage, and that is no guarantee either. A healthy lifestyle has no downside. Embracing it might just save your life!

Christmas is just round the corner and most people will be attending a few Christmas lunches or dinners at work or with friends. Everyone is ready for a good nosh up and making merry, and so you should! Perhaps you might consider making it more interesting by observing who eats quickly and who eats until full, or both. ‘What for?’ you might enquire.

A study from Japan studied 4140 adults (1496 men, 2644 women), aged 30 – 69 years, living in Ikawa, a rural community in the north east of Japan, and Yao, a suburb in the south west (BMJ 2008; 337: a2002) . In this population, they examined whether eating until full, eating quickly or both are associated with being overweight (BMI ≥ 25). Overall, 50.9% (571) men and 58.4% (1265) women reported eating until full and 45.6% (523) men and 36.3% (785) women reported eating quickly (fast and very fast categories). In the eating until full group the men are 2 times and women are 1.92 times more likely to be obese when compared to those not eating until full. In the eating quickly group, both men (1.84 x) and women (2.09 x) are more likely to be obese when compared to those who did not eat quickly. As for those who eat quickly and eat until full, the risk of being overweight was 3.13 for men and 3.21 for women. This observation is not unique to the Japanese. In fact, in 1996, a study among fireman and paramedics in USA showed similar findings (Prev Med 1996; 25: 593 – 600).

Do enjoy yourself at the Christmas gathering but remember, don’t rush and don’t gorge! Have a Very Merry Christmas!