In the Journals

Alternate-day fasting ineffective for weight loss

Alternating fasting days in patients with obesity was not significantly more effective regarding adherence, weight loss, weight maintenance or cardioprotection than restricting daily calorie intake, according to findings published in JAMA Internal Medicine.

“The first-line therapy prescribed to obese patients for weight loss is daily calorie restriction,” John F. Trepanowski, PhD, from the department of kinesiology and nutrition at the University of Illinois at Chicago, and colleagues wrote. “However, many patients find it difficult to adhere to a conventional weight-loss diet because food intake must be limited every day. As such, adherence to daily calorie restriction decreases after 1 month and continues to decline thereafter. In light of this limitation, another approach that requires individuals to restrict calories only every other day was developed. This strategy is called alternate-day fasting and involves a fast day where individuals consume 25% of their usual intake (approximately 500 kcal), alternated with a ‘feast day’ where individuals are permitted to consume food ad libitum.”

“Despite the growing popularity of alternate-day fasting, to our knowledge, no long-term randomized clinical trials have evaluated its efficacy or compared this regimen with a conventional weight-loss diet,” they added.

Between Oct. 1, 2011 and Jan. 15, 2015, Trepanowski and colleagues conducted a randomized clinical trial of 100 metabolically healthy obese adults (86 women) aged 18 and 64 years with a mean BMI of 34 kg/m2 to determine if alternate-day fasting is more effective than daily calorie restriction for weight loss and weight maintenance. They also evaluated adherence to the dietary intervention and risk indicators for CVD. For 1 year, participants were randomly assigned to one of three groups: alternate-day fasting and feasting (25% and 125% of energy needs, respectively), calorie restriction (75% of energy needs every day) or a no-intervention control. The weight-loss phase consisted of 6 months and was followed by a weight-maintenance phase that consisted of another 6 months.

The highest dropout rate was in the alternate-day fasting group (38%) relative to the calorie-restriction group (29%) and control group (26%). In comparison to the control group, the alternate-day fasting group and the daily calorie restriction group had similar mean weight loss at 6 months (–6.8% vs. –6.8%) and 12 months (–6% vs. –5.3%). The researchers noted that participants in the daily calorie restriction group largely met their goals of energy consumption, whereas those in the alternate-day fasting group consumed more food than prescribed on fast days and less food than prescribed on feast days.

At 6 and 12 months, there were no significant differences in BP, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein or homocysteine concentrations among intervention groups. Compared with participants in the daily calorie restriction group, those in the alternate fasting group displayed significantly increased mean high-density lipoprotein cholesterol levels at 6 months (6.2 mg/dL; 95% CI, 0.1-12.4); however, this increase was not observed at 12 months (1 mg/dL; 95% CI, –5.9 to 7.8). In addition, the alternate-day fasting group had significantly higher mean LDL cholesterol levels (11.5 mg/dL; 95% CI, 1.9-21.1) than the daily calorie restriction group.

“Alternate-day fasting has been promoted as a potentially superior alternative to daily calorie restriction under the assumption that it is easier to restrict calories every other day,” Trepanowski and colleagues concluded. “However, our data ... indicate that this assumption is not the case. Rather, it appears as though many participants in the alternate-day fasting group converted their diet into de facto calorie restriction as the trial progressed.”

“These findings suggest that alternate-day fasting may be less sustainable in the long term, compared with daily calorie restriction, for most obese individuals,” they added. “Nevertheless, it is still possible that a certain smaller segment of obese individuals may prefer this pattern of energy restriction instead of daily restriction. It will be of interest to examine what behavioral traits (eg, ability to go for long periods without eating) make alternate-day fasting more tolerable for some individuals than others.” – by Alaina Tedesco

Disclosure: The researchers report receiving support from the National Institutes of Health/National Heart, Lung, and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases.

 

Alternating fasting days in patients with obesity was not significantly more effective regarding adherence, weight loss, weight maintenance or cardioprotection than restricting daily calorie intake, according to findings published in JAMA Internal Medicine.

“The first-line therapy prescribed to obese patients for weight loss is daily calorie restriction,” John F. Trepanowski, PhD, from the department of kinesiology and nutrition at the University of Illinois at Chicago, and colleagues wrote. “However, many patients find it difficult to adhere to a conventional weight-loss diet because food intake must be limited every day. As such, adherence to daily calorie restriction decreases after 1 month and continues to decline thereafter. In light of this limitation, another approach that requires individuals to restrict calories only every other day was developed. This strategy is called alternate-day fasting and involves a fast day where individuals consume 25% of their usual intake (approximately 500 kcal), alternated with a ‘feast day’ where individuals are permitted to consume food ad libitum.”

“Despite the growing popularity of alternate-day fasting, to our knowledge, no long-term randomized clinical trials have evaluated its efficacy or compared this regimen with a conventional weight-loss diet,” they added.

Between Oct. 1, 2011 and Jan. 15, 2015, Trepanowski and colleagues conducted a randomized clinical trial of 100 metabolically healthy obese adults (86 women) aged 18 and 64 years with a mean BMI of 34 kg/m2 to determine if alternate-day fasting is more effective than daily calorie restriction for weight loss and weight maintenance. They also evaluated adherence to the dietary intervention and risk indicators for CVD. For 1 year, participants were randomly assigned to one of three groups: alternate-day fasting and feasting (25% and 125% of energy needs, respectively), calorie restriction (75% of energy needs every day) or a no-intervention control. The weight-loss phase consisted of 6 months and was followed by a weight-maintenance phase that consisted of another 6 months.

The highest dropout rate was in the alternate-day fasting group (38%) relative to the calorie-restriction group (29%) and control group (26%). In comparison to the control group, the alternate-day fasting group and the daily calorie restriction group had similar mean weight loss at 6 months (–6.8% vs. –6.8%) and 12 months (–6% vs. –5.3%). The researchers noted that participants in the daily calorie restriction group largely met their goals of energy consumption, whereas those in the alternate-day fasting group consumed more food than prescribed on fast days and less food than prescribed on feast days.

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At 6 and 12 months, there were no significant differences in BP, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein or homocysteine concentrations among intervention groups. Compared with participants in the daily calorie restriction group, those in the alternate fasting group displayed significantly increased mean high-density lipoprotein cholesterol levels at 6 months (6.2 mg/dL; 95% CI, 0.1-12.4); however, this increase was not observed at 12 months (1 mg/dL; 95% CI, –5.9 to 7.8). In addition, the alternate-day fasting group had significantly higher mean LDL cholesterol levels (11.5 mg/dL; 95% CI, 1.9-21.1) than the daily calorie restriction group.

“Alternate-day fasting has been promoted as a potentially superior alternative to daily calorie restriction under the assumption that it is easier to restrict calories every other day,” Trepanowski and colleagues concluded. “However, our data ... indicate that this assumption is not the case. Rather, it appears as though many participants in the alternate-day fasting group converted their diet into de facto calorie restriction as the trial progressed.”

“These findings suggest that alternate-day fasting may be less sustainable in the long term, compared with daily calorie restriction, for most obese individuals,” they added. “Nevertheless, it is still possible that a certain smaller segment of obese individuals may prefer this pattern of energy restriction instead of daily restriction. It will be of interest to examine what behavioral traits (eg, ability to go for long periods without eating) make alternate-day fasting more tolerable for some individuals than others.” – by Alaina Tedesco

Disclosure: The researchers report receiving support from the National Institutes of Health/National Heart, Lung, and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases.