People who fast every other day don’t necessarily lose more weight than dieters who cut calories in other ways, finds a new U.S. study from the University of Illinois at Chicago.
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.
What is alternate day fasting?
An alternative to daily calorie restriction, alternate day fasting allows you to eat normally on certain days and then fast (water and low calorie drinks are permitted) or drastically cut your calorie intake on other days. Most protocols have dieters eat 500 to 600 calories every other day.
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.
Participants were around 44 years old on average, and 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.
Dfference in pounds lost not significant
At the end of the year, 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.
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. More dropouts were due to dissatisfaction with the diet in the fasting group than the other group.
The findings suggest that alternate day fasting may not be a sustainable long-term option for weight loss.
One concern about fasting is that it might exacerbate a dieter’s relationship with food or lead to an increased risk of extreme eating behaviors like binging.
Another downside of intermittent fasting is that it does not teach strategies for adopting and maintaining a healthy lifestyle or for overcoming obstacles to staying on track.
Source: JAMA Internal Medicine, online May 1, 2017.
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