Published: Nov 18, 2013 | Updated: Nov 18, 2013
By Kristina Fiore, Staff Writer, MedPage Today

Full Story:  http://www.medpagetoday.com/MeetingCoverage/ObesityWeek/42966

ATLANTA — Adopting a habit of “intermittent fasting” that involves foregoing food every other day may eventually lead to weight loss and improve cognition in heavier patients, researchers reported here.

In a single-center, randomized, pilot study, patients who fasted completely every other day lost about the same amount of weight over 2 months as those who didn’t fast at all, William Troy Donahoo, PhD, of Kaiser Permanente Colorado, and colleagues reported during a poster session at Obesity Week.

But at 6 months, after patients were technically off the intervention, those who had the initial “intermittent fasting” intervention had greater weight loss and greater improvements in cognitive function than those on a standard diet, Donahoo reported.

“This is a preliminary finding that’s similar to what has been seen in mice,” Donahoo toldMedPage Today. “It is likely due to people continuing some level of fasting after the study ended.”

Other reasons for the late improvements, Donahoo speculated, were that the 8-week period wasn’t long enough to see the effects of the diet, and fasters may have continued their routines during the next 4 months. Or, he said, the 8 weeks of fasting led to an improved metabolic state that offered delayed benefits, “perhaps being more flexible with shifting between carbs and fat for fuel, or less leptin resistant.”

Intermittent fasting involves restricting the hours for caloric intake; typically an 8-hour window in the middle of the day, although other variations exist. These include alternate-day fasting — in which patients consume either very few calories (500 or 600) or fast completely every other day — or the 5:2 diet in which one eats normally 5 days per week with 2 days limited to few or no calories.

Although the diet has only recently garnered national attention, researchers have been studying its benefits for years. Co-author Mark Mattson, PhD, of the National Institute on Aging in Baltimore, has looked at the effects of intermittent fasting on the brains of rats and mice for the past 15 years. That research has shown significant cognitive benefits with fasting, Mattson told MedPage Today.

The current study, he said, is the first to show the cognitive benefits of intermittent fasting in humans.

“These new findings are consistent with our previous studies in animal models,” Mattson toldMedPage Today.

Donahoo and colleagues enrolled 26 obese but otherwise healthy people, ages 23 to 55, who had a mean body mass index (BMI) of 37 kg/m². The majority of the participants were women (20).

They were randomized either to a variation of intermittent fasting — total fasting every other day, with no restrictions on calorie intake on “feeding” days — or to a standard dietary intake.

Participants were assessed after 8 weeks on the diet during a 2-day inpatient visit. They underwent cognitive tests and had blood drawn to look for brain-derived neurotrophic factor(BDNF), IL-6, TNF-alpha, CRP, cholesterol, lipids, leptin, and ghrelin. They also had measurements of 24-hour salivary free cortisol, as well as a glucose tolerance test on the second day.

They were then followed through to 6 months, after the intervention had stopped, and were re-assessed for those parameters.

Donahoo and colleagues found no significant differences in any of the measurements at 2 months. Those in the intermittent fasting group lost a mean 6.5% of body weight compared with a loss of 5.75% in the standard diet group. Fat mass, trunk fat, and cognitive function were also similar between groups at that time.

But by 6 months, those who had fasted during the initial 2 months of the trial had significantly greater weight loss than those in the standard diet group — probably because they maintained some of the principles of the intermittent fasting diet during that time, Donahoo said.

Fasters also had less fat mass and trunk fat at that time, as well as significantly greater improvements in memory (P=0.013).

The researchers also reported a trend toward increased BDNF, a marker of cognitive function (P=0.07), as well as a trend for toward improved insulin sensitivity compared with the standard diet at that time.

Donahoo concluded that the study offers “preliminary evidence of enduring visceral fat-reducing and cognition-enhancing alternate-day intermittent fasting in humans.”

In an earlier paper, Mattson wrote that intermittent fasting is consistent with the way humans evolved to eat. “From an evolutionary perspective, intermittent fasting is normal, and eating 3 meals a day plus snacks is abnormal. Going without food for most of the day or even for several days is a challenge that we are very capable of meeting,” he stated.