A new book, Greg Critser’s Fat Land attempts to focus attention on a new health crisis: the growing prevalence of obesity and poor physical fitness in the United States. During the past several years, both the popular media and the medical literature have drawn attention to the growing numbers of overweight persons. The prevalence of obesity has risen from 12 per cent of adults in 1991 to more than 20 per cent in 2001. Obesity rates for adolescents between the ages of 12 and 19 have tripled in the past 25 years, increasing from 5 per cent to the current 15 per cent.

Fast-food marketing efforts also aligned to change the way, and the amount, we eat. As Critser explains, once the staples used to make fast food became cheaper, marketers induced consumers to buy and eat more of them. French-fry vendors in the 1970s noticed that even though consumers ‘scrape and pinch around the bottom of the bag for more and eat the salt,’ fear of looking ‘piggish’ kept them from buying two bags. Consumer reluctance to go back for seconds was overcome by increasing portion sizes, and ‘super-sizing’ was born. A serving of McDonald’s fries ‘ballooned from 200 calories (1960)...to the present 610 calories.’ Satiety expanded to meet the larger portions. Critser cites research showing that our appetites are not fixed; when presented with more food, we learn to clean our larger plates. Between 1977 and 1995, average daily food intake increased by almost 200 calories.

The belief that early detection is the key to survival has been greatly strengthened by the high public profile of screening programmes for cancers affecting women. It is not surprising that, even though the evidence for this conviction is disputed, the demand for screening has spread to our increasingly health-conscious male patients.

Controversies about the benefits of mammography rage on. While some epidemiological studies indicate that routine mammography screening does save lives, others dispute this. Some believe that the benefits of prevention are bought at too high a cost and that resources would be better spent on treatment.

A study published last month suggests that cervical smears do save lives, but at a price higher than can be measured in monetary terms (Raffle A, et al. BMJ 2003;326:901–4). For every death prevented, 1000 women endure an adult lifetime of regular smears – and one of these women still dies from undiagnosed cervical cancer despite having smears. Of these 1000 women, some 150 endure the distress and anxiety of an ‘abnormal’ smear report and 80 are referred for further specialist treatment. Although more than 80% of cases of high-grade dyskaryosis and high-grade dysplasia do not progress to invasive cancer, all are currently treated surgically.

As the authors of the cautionary study of the cervical smear programme point out, if men continue to pursue their demands for screening test of dubious value, ‘the net result will be major iatrogenic harm from invasive investigations and treatments’.

The blood test that measures prostate specific antigen (PSA) to detect prostate cancer often produces false positive results and should be repeated at least once before an invasive biopsy is performed, a new study says.

‘We recommend having the findings confirmed by repeating the test after waiting at least six weeks,’ said Dr James Eastham, a surgeon in the department of urology at the Memorial Sloan-Kettering Cancer Center in New York and lead author of the study.

‘Even if the repeat test shows an elevated level, prostate cancer will only be discovered in about one quarter of men who undergo biopsy...A single, elevated PSA level does not automatically warrant a prostate biopsy,’ he said.

Concentrations above 4.0 ng/ml can signal prostate cancer, but not always – sometimes a rise in PSA is due to another cause, and sometimes cancer can occur without a rise. About a fifth of aggressive prostate tumours are found in men with normal PSA concentrations.

False positive results are common, because cancer is not the only cause of raised PSA concentrations. Inflammation can increase them, as can recent ejaculation. And the enlargement of the prostate that occurs normally with age brings a gradual increase. The new study indicates that natural fluctuation can also lead to high results of the test.

Scientists at biotech giant Genzyme say that many supposedly different kinds of adult stem cells – which hold enormous promise for treating disease – are in fact indistinguishable.

Because adult stem cells are present in everyone, they are easier to obtain than the embryonic stem cells taken from 10-day-old embryos, and far less controversial. Until recently, however, it was thought they had only limited potential.

That changed last year, when New Scientist revealed that Catherine Verfaillie of the University of Minnesota had discovered ‘multipotent adult progenitor cells’, or MAPCs, apparently capable of giving rise to all tissues in the body, just like embryonic stem cells.

Another promising kind of adult stem cell is Osiris Therapeutics’ mesenchymal stem cell. MSCs have only been shown to make a handful of tissues such as bone, cartilage, fat and muscle, but have a remarkable property: they seem to cause little or no immune reaction when transplanted.

But according to Ross Tubo of Genzyme, the MAPCs and MSCs are one and the same. Put the properties of the two kinds of cell together and all of a sudden you have a non-controversial, highly versatile source of adult stem cells that can, in theory, be transplanted to anyone. This truly would be the ultimate stem cell.