Dieters already have been turning away from Atkins-style plans as a long-term
weight-control strategy, and the new study gives them more reason: Low-fat plans
seem to work better at keeping weight off.
"People who started eating more fat ... regained the most weight over time,"
said Suzanne Phelan, a Brown Medical School psychologist who presented results
of the study Monday at a meeting of the North American Association for the Study
of Obesity.
The study used the National Weight Control Registry, a decade-old effort to
learn the secrets of success from people who had lost at least 30 pounds and
kept them off for at least a year. The registry run by doctors from the
University of Colorado in Denver, the University of Pittsburgh and Brown
University in Providence, R.I.
They studied 2,700 people who entered the registry from 1995 through 2003.
Their average age was 47, most were women, and they had lost an average of 72
pounds initially. Doctors compared their diets to see whether one type or
another made a difference in how much weight they had lost and how much they had
regained a year later.
All reported eating only about 1,400 calories a day, but the portion that
came from fat rose — from 24 percent in 1995 to more than 29 percent in 2003 —
while the part from carbohydrates fell, from 56 percent to 49 percent.
The number who were on low-carb diets (less than 90 grams a day) rose from 6
percent to 17 percent during the same period.
The type of diet — low-fat, low-carb or in between — made no difference in
how people lost weight initially.
But those who increased their fat intake over a year regained the most
weight. That meant they ate less carbohydrates, because the amount of protein in
their diets stayed the same, Phelan said.
"Only a minority of successful weight losers consume low-carbohydrate diets,"
she and the other researchers concluded.
Colette Heimowitz, a nutrition expert and spokeswoman for the Atkins diet
organization, noted that the study considered 90 grams to be low-carb, while
Atkins recommends 60 grams for weight loss and 60 to 120 for weight maintenance.
She said that for many of the dieters studied, "the carbs aren't low enough
for them to be successful." They also should have replaced carbs with more
protein rather than fat, she said.
Dr. Thomas Wadden, a University of Pennsylvania weight loss expert who had no
role in the study, said it is too soon to say which approach is better. Several
longer-term studies of low-carb and low-fat dieters are in the works, he said.
But he said: "I do think that people who are keeping the weight off are
eating a low-fat, high-carb diet."
The dietary establishment has long been skeptical of the long-term safety and
effectiveness of low-carb diets, and consumers increasingly are losing their
enthusiasm for the glut of low-carb products that overloaded grocery store
shelves as the diet became a fad in the past few years.
More than half of Americans who have tried a low-carb diet have given up,
according to a recent survey by the market research firm InsightExpress. Other
published survey information suggests that the number of Americans following
such a diet peaked at 9 percent last February and fell to 6 percent by June.
The American Institute for Cancer Research used those trends to issue a
statement in September urging dieters to "come back to common sense."
"Eat a balanced diet weighted toward vegetables and fruits, reduce portion
sizes and increase physical activity," the institute said.
Dr. William Dietz, director of chronic-disease prevention at the federal
Centers for Disease Control and Prevention, said it is difficult to tell whether these
low-carb diets really work because people find it hard to stick to a strict
regimen for long periods.
"My anecdotal experience is that people go on and off these diets," he said.
"When their weight goes up, they go back on the diet to lose weight."
Other research at the conference underscored the many health and personal
problems obese people face.
Duke University doctors said two-thirds of obese people seeking treatment at
the Duke Diet & Fitness Center reported not enjoying or wanting to have sex,
and having problems with sexual performance. Only 5 percent of normal-weight
people from the surrounding community who completed the same quality-of-life
survey reported such problems.
