http://www.medicalnewstoday.com/healthnews.php?newsid=67422

Perhaps most of us knew this already, but the summary is good.
Key line: "dieting is actually a consistent predictor of future weight
gain."

Morris
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Scientists Say Dieting Does Not Work
10 Apr 2007

US scientists conducting a comprehensive review of dieting research
have concluded that dieting does not work.

The study is published in the April edition of American Psychologist,
the journal of the American Psychological Association.

Researchers at the University of California, Los Angeles (UCLA),
reviewed 31 long-term studies lasting between 2 to 5 years.

UCLA associate professor of psychology and lead author of the study,
Traci Mann said:

"You can initially lose 5 to 10 percent of your weight on any number
of diets, but then the weight comes back."

"We found that the majority of people regained all the weight, plus
more," she added.

The researchers found a very small minority of study participants
managed to sustain weight loss, while the majority put all the weight
back on, and more in the longer term.

"Diets do not lead to sustained weight loss or health benefits for the
majority of people," said Dr Mann.

Dr Mann and colleagues sought to determine the long term effects of
dieting and address the question "Would they have been better off to
not go on a diet at all?".

So they analyzed every study they could find that followed people on
diets for 2 to 5 years. Studies that take less than 2 years are "too
short to show whether dieters have regained the weight they lost,"
they said.

They discovered that it would have been better for most of them if
they had not gone on a diet at all.

"Their weight would be pretty much the same, and their bodies would
not suffer the wear and tear from losing weight and gaining it all
back," explained Dr Mann.

Their findings show that:

-- People on diets typically lose 5 to 10 per cent of their weight in
the first 6 months.
-- But 33 to 66 per cent regain more than what they lose within 4 to 5
years.

Dr Mann and colleagues suspect the real situation is actually even
worse; the figures do not really reflect reality, making diet studies
look better than they are. They say there are a number of reasons for
this:

-- Many participants phone or mail their results in themselves,
without an impartial assessor.
-- A lot of studies have a below 50 per cent follow up rate; and the
people who put on a lot of weight are less likely to stay in touch.

UCLA graduate student of psychology and co-author of the study, Janet
Tomiyama said that "Several studies indicate that dieting is actually
a consistent predictor of future weight gain."

One study in particular that they looked at found that men and women
who took part in a weight reduction programme gained significantly
more weight than those who did not over the same period of time.

Tomiyama mentioned another study, this time looking at links between
lifestyle and weight in 19,000 healthy older men over four years. This
study found that, "One of the best predictors of weight gain over the
four years was having lost weight on a diet at some point during the
years before the study started," she said.

Also, in many studies with control groups, the people in the control
group very often were better off than the participants who dieted.

Dr Mann suggests that eating in moderation and exercise do make a
difference. Although they were not looking at exercise in particular,
Dr Mann said that:

"Exercise may well be the key factor leading to sustained weight loss.
Studies consistently find that people who reported the most exercise
also had the most weight loss."

One study following obese patients discovered that:

-- Among those followed for under 2 years, 23 per cent of patients had
regained their weight loss.
-- Among those followed for more than 2 years, 83 per cent had
regained their weight loss.

Another study found that 50 per cent of dieters weighed 11 pounds (5
kilos) more than their starting weight 5 years after their diet.

Among the health hazards of repeated weight loss and regain are
cardiovascular disease, stroke, diabetes and altered immune function,
said Dr Mann and colleagues.

They said more research is needed on the effects of weight loss and
regain on health, and say scientists do not fully understand the
underlying factors involved in this complex relationship.

Dr Mann quoted her mother, who herself has tried to diet many times,
without success. Dr Mann's mother said her daughter's findings were
"obvious".

Although this study reviewed 31 long term dieting projects, they did
not look into specific diets.

The researchers are of the opinion that weight loss programmes are not
good value for money in the treatment of obesity.

"The benefits of dieting are too small and the potential harm is too
large for dieting to be recommended as a safe, effective treatment for
obesity," said Dr Mann.

Between 1980 and 2000, the proportion of obese Americans has doubled,
from 15 to 31 per cent of the population.

Written by: Catharine Paddock
Writer: Medical News Today