More bad news for big boys.

Research by from Manchester suggests that tubby men are at far greater risk of developing bowel cancer - the second biggest cancer killer after lung cancer - than women. A study of 221 previously published studies - 282,137 cancer cases in all - concluded that an increase of 5kg per square metre in body mass index equalled a 25% increase in bowel cancer risk.

The risk of other cancers was also up in obese men - gullet cancer by 50%, thyroid cancer by 33% and kidney cancer by 25%. There was also a slight link with rectal cancer, malignant melanoma, leukaemia, multiple myeloma and non-Hodgkin's lymphoma.

If that's not enough, research from the US suggests that a big waistline in your 40s could almost triple your risk of Alzheimer's Disease or other forms of dementia in old age. Indeed, according to the study of 6,583 people published in Neurology, a big tummy can increase your risk even if you're actually not overweight.

It is not clear why being overweight may affect your ageing brain, but it could be that the problems already associated with obesity such as high blood pressure, diabetes and high cholesterol levels may have an effect. Also a lot of fat around the middle of the body may mirror the levels of fat around the major organs of the body including the brain.

In the study, which followed people from their 40s into their 70s, the 20% of people with the largest waistlines had a 270% greater risk of dementia than those with the smallest waists. But, even those reckoned to be normal weight using body mass index calculations had approximately a 90% increased risk of dementia if they had a large rather than a small waist while those who were measured as overweight or obese using body mass index, but didn't have a large belly, had an 80% increase in dementia risk.

In other words, a large belly looks to be as big a risk factor as being generally overweight while being both is very risky indeed.