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 Fasting regimens that involve alternate-day calorie restriction have
become increasingly popular, in part because some people struggle to
shed excess pounds by conventional diets focused on counting
calories every single day, the research team notes in JAMA Internal
Medicine.
For the study, researchers randomly assigned 100 obese adults to
three different groups. One group stuck to their normal eating
habits for one year. Two other groups reduced their calorie intake,
either by fasting every other day or by cutting back daily but by a
less extreme amount. Both dieting groups cut back on similar amounts
of calories overall.
At the end of the year, the fasting group did lose more weight than
the other dieters, but the difference wasn’t big enough to rule out
the possibility that it was due to chance.
“I think this study says that alternate day fasting is not the magic
bullet that it has been hyped to be,” said Susan Roberts, director
of the Energy Metabolism Lab at the USDA Nutrition Center at Tufts
University in Boston.
“This is not the same thing as saying that it is useless, either,
since some people may find it helpful,” Roberts, who wasn’t involved
in the study, said by email. “And similarly, I don’t think we can
conclude from this that all calories are the same.”
Participants were around 44 years old on average. Most were female.
In the fasting group, participants alternated between cutting
calories by 75 percent on one day and then increasing intake by 25
percent on the next day.
By contrast, dieters in the other group consistently cut calories by
25 percent.
In both diet groups, researchers gave participants prepared meals
for three months and then offered dietary counseling afterward.
Compared to the control group of participants who weren’t asked to
diet, each of the diet groups did lose more weight: a 6 percent
total weight loss for the fasting group and 5.3 percent for the
calorie restriction group. But the difference between the results
from each of the calorie cutting regiments wasn’t statistically
meaningful.
The two calorie-cutting options were no better than normal eating
habits for reducing risk factors for heart disease like blood
pressure and total cholesterol levels.
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One limitation of the study, beyond its small size, is that a lot of
participants dropped out before it ended, including 38 percent of
the fasting group and 29 percent of the calorie restriction group,
the authors note. More dropouts were due to dissatisfaction with the
diet in the fasting group than the other group, the researchers also
found.
This suggests that alternate day fasting may not be a sustainable
long-term option for weight loss, senior study author Krista Varady
of the University of Illinois at Chicago and co-authors write.
“The jury is still out – especially on how healthy and sustainable
this approach is,” said Samantha Heller, a nutritionist at New York
University Langone Medical Center in New York City who wasn’t
involved in the study.
One concern about fasting is that it might exacerbate a dieter’s
complex relationship with food or lead to an increased risk of
extreme eating behaviors like binging, Heller said by email.
“Intermittent fasting does not teach strategies for adopting and
maintaining a healthy lifestyle or for managing life’s ups and
downs,” Heller added. “A lifestyle overhaul, one that a person can
maintain for long term that provides a healthy, balanced diet as
well as pleasurable foods is what I would like to see people
embrace.”
SOURCE: http://bit.ly/2pnWraR JAMA Internal Medicine, online May 1,
2017.
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