Sunday, March 25, 2007

Is dieting good for you?

The authors of "Diet Nation" argue that efforts to lose weight are generally doomed to failure - and may possibly cause more harm than good

By this time of year, most New Year's resolutions to lose weight have long since bitten the dust. But actually, the prospects for successful dieting are never good. Out of every 100 people who diet, only four are able both to lose weight and to maintain their post-diet weight. When it comes to dieting, most of us are hopeless recidivists. Most of us also refuse to accept such glum news. Our image of what constitutes our correct weight and body size, dictated by a media and public health community obsessed with obesity, continues to drive both women and men to attempt something that is largely impossible. Worse, if there is a health effect of dieting, it may actually be detrimental rather than beneficial.

Research finds that 90 per cent of American high school girls are dieting, despite the fact that many are not overweight or obese. A 2001 study of female high school students by Brigham Young University researchers found that 11 per cent had used laxatives to lose weight, 15 per cent had taken appetite control pills, and nine per cent had made themselves vomit after eating. Almost half of these girls restricted their food intake to a mere 1,200 calories a day or less. The World Health Organisation defines starvation as a diet of less than 900 calories per day, yet many diets only allow between 950 and 1,200 calories per day. A recent survey of women's eating habits found that the median caloric intake is only about 1,600 calories per day, even though the recommended dietary allowance (RDA) for adult women is 2,200 daily calories.

As Jane Ogden of King's College, London writes in Fat Chance: The Myth of Dieting Explained: `For the large majority of women, dieting does not work. Dieting creates more problems than it solves; dieting and overeating become a vicious circle. Dieters never stop dieting, and never stop using the dieting industry.'

The evidence that diets are doomed to failure is extensive. Several studies that have looked at dieting, diet types and weight-loss counselling have concluded that attempts at weight loss are largely unsuccessful, even in highly controlled situations. In a study that compared low carbohydrate and low fat diets, researchers found that adherence was poor and attrition was high in both groups. Another study that compared self-help diets with commercial diet plans found that after two years the differences in the two groups were negligible.

A review of the major commercial weight loss programs concluded that even the comparatively successful programmes were characterised by `high costs, high attrition rates, and a high probability of regaining 50 per cent or more of lost weight in one to two years'. One shudders to think about the odds of the less successful ones. As the US National Institutes of Health's review of weight loss programmes put it, `Regardless of the products used, successful weight loss. was limited'.

The reasons for such failures are not always found in a lack of willpower. Our metabolic rate conspires against sustained weight loss by decreasing in response to reduced caloric intake so the body can still function. Some experts suggest that a fortnight of dieting can lead to a 20 percent decline in metabolic rate. This sets up a vicious cycle in which it becomes progressively more difficult to lose each additional pound, as the dieter's body uses food more efficiently and draws less from its reserve of fat.

The difficulties of dieting are usually put to one side when compared to the alleged health benefits. After all, don't people who lose weight have a lower risk of heart disease and type-2 diabetes? But those who accept the evidence about the dangers of obesity, based on epidemiological studies, should also be aware that there is equally strong evidence from such studies that dieting is bad for you. A National Institutes of Health conference that reviewed the evidence about dieting concluded: `Most studies, and the strongest science, shows weight loss. is actually strongly associated with increased risks of death - by as much as several hundred per cent.'

Dieters have double the risk of getting type-2 diabetes compared to those who are overweight but do not diet. The connection between weight loss and increased risk for an early death is particularly striking in two large studies - the Iowa Women's Health Study and the American Cancer Society study. In the follow-up to the American Cancer Society study, researchers found that healthy obese women were in fact better off not losing weight. Healthy women who lost weight had increased mortality risks from cancer, cardiovascular disease, and all other diseases when compared to healthy women who did not diet. A later study found comparable results for men.

Over the past 20 years, more than two dozen studies have found that weight losses of 20 to 30 pounds (between nine and 13 kilos) - the amount most dieters say they want to lose - lead to an increased risk of premature mortality. During the same period, only four studies have found that losing weight increases life expectancy. Commenting on the gain in life expectancy from such efforts, author and commentator Paul Campos notes that one study `found an eleven-hour increase in life expectancy per pound lost. the equivalent of an extra month of life in return for a permanent 50 pound weight loss'.

Rather than lamenting our inevitable fall off the dieting wagon, perhaps we should resolve to take our slightly plump selves as a testimony not to bad health but good health. Let's raise a well-laden fork to resolving not to think about dieting again until next year.


New prostate cancer drug

An experimental drug designed to fight the spread of aggressive prostate cancer is showing great promise for future sufferers, Australian developers say. A team from the University of New South Wales is working on a new therapy for prostate cancer patients who stop responding to standard hormone treatments. The medication is still in the development stage but if new tests prove successful, it could bring relief for a group of men for whom there is currently no treatment, said study leader Dr Kieran Scott. "We've seen enough positive data to know it's worth testing in people," Dr Scott said.

Prostate cancer is the most common cancer in Australian men, with patients usually treated with some combination of surgery, radiation and hormone medications. These drugs effectively limit the spread of prostate cancer in the early stages by suppressing the male hormones that tumours need to grow. But over time cancers often stop responding to this treatment, putting men at risk of tumour growth and cancer spread to the bones.

Dr Scott said his team at St Vincent's Hospital in Sydney believed it had a new oral medicine that could slow the growth of hormone-resistant cancer and stop its spread. The medication works by blocking an enzyme which releases Omega-6 fatty acids - fats which, when consumed in the diet, have been associated with increased rates of disease. "We think we can slow the growth of tumours that are resistant and we believe the drug may also help slow the growth of tumours in bones," Dr Scott said. "If we can help in those two areas then we'll have a therapy for prostate cancer patients who currently have no good treatment."

The team has been granted Cancer Council NSW funding for a new round of tests, with plans to manufacture and trial the experimental compound in the most severely-affected patients if they have success. "I've been working in this area for 10 or 15 years and to be honest I didn't think this would work," Dr Scott said. "But the data keeps me going because it keeps suggesting this approach really will work."

Other cancer grants awarded include an investigation of genes that predispose people to melanoma and a study of new techniques to minimise breast cancer surgery side-effects.



Just some problems with the "Obesity" war:

1). It tries to impose behavior change on everybody -- when most of those targeted are not obese and hence have no reason to change their behaviour. It is a form of punishing the innocent and the guilty alike. (It is also typical of Leftist thinking: Scorning the individual and capable of dealing with large groups only).

2). The longevity research all leads to the conclusion that it is people of MIDDLING weight who live longest -- not slim people. So the "epidemic" of obesity is in fact largely an "epidemic" of living longer.

3). It is total calorie intake that makes you fat -- not where you get your calories. Policies that attack only the source of the calories (e.g. "junk food") without addressing total calorie intake are hence pissing into the wind. People involuntarily deprived of their preferred calorie intake from one source are highly likely to seek and find their calories elsewhere.

4). So-called junk food is perfectly nutritious. A big Mac meal comprises meat, bread, salad and potatoes -- which is a mainstream Western diet. If that is bad then we are all in big trouble.

5). Food warriors demonize salt and fat. But we need a daily salt intake to counter salt-loss through perspiration and the research shows that people on salt-restricted diets die SOONER. And Eskimos eat huge amounts of fat with no apparent ill-effects. And the average home-cooked roast dinner has LOTS of fat. Will we ban roast dinners?

6). The foods restricted are often no more calorific than those permitted -- such as milk and fruit-juice drinks.

7). Tendency to weight is mostly genetic and is therefore not readily susceptible to voluntary behaviour change.

8). And when are we going to ban cheese? Cheese is a concentrated calorie bomb and has lots of that wicked animal fat in it too. Wouldn't we all be better off without it? And what about butter and margarine? They are just about pure fat. Surely they should be treated as contraband in kids' lunchboxes! [/sarcasm].

Trans fats:

For one summary of the weak science behind the "trans-fat" hysteria, see here. Trans fats have only a temporary effect on blood chemistry and the evidence of lasting harm from them is dubious. By taking extreme groups in trans fats intake, some weak association with coronary heart disease has at times been shown in some sub-populations but extreme group studies are inherently at risk of confounding with other factors and are intrinsically of little interest to the average person.