1. Based on this randomized clinical trial, alternate-day fasting did not yield different results with regards to weight loss, blood pressure, or lipid profiles compared to a typical, caloric-restriction strategy.
2. The alternate-day fasting strategy had significantly worse compliance compared to calorie restriction or control.
Evidence Rating Level: 2 (Good)
Study Rundown: Obesity remains one of the top public health issues in the developed world. Efforts for weight loss often involve increased physical activity and caloric restriction. Due to poor compliance with typical restriction strategies, an alternate-day fasting model has emerged. The current study sought to compare an alternate-day fasting approach to traditional calorie restriction and no intervention to investigate for any specific weight loss and metabolic benefits. Weight loss was not different between the two intervention groups, but was more than in the control group. Blood pressure, heart rate, insulin, C-reactive protein, triglyceride, and HDL levels did not differ in long-term follow up between the two intervention groups. The alternate-day fasting group had worse adherence and a greater dropout rate than with the traditional restriction or control groups.
The strengths of the study included randomized control design, controlling for known covariates, and long length of follow-up. Weaknesses of the study included the high rate of dropout, particularly in the alternate-day fasting group. While the drop-out rate may reflect a real-world scenario, it does hinder the ability of the study to determine the effectiveness of the alternate-day fasting model. The study population was also predominantly female and black, and may not be generalizable to other populations.
In-Depth [randomized controlled trial]: This study enrolled patients from 2011 to 2015 at a single institution at the University of Illinois. Adults 18 to 65 years of age were included if they had a body mass index between 25.0 and 39.9 and were sedentary (<60 minutes of light activity/week). Participants were excluded if they had established cardiovascular disease, diabetes, medications that could affect study outcomes, unstable weight, pregnancy, perimenopause, or were active smokers. Randomization occurred in a 1:1:1 ratio, with a 1-month baseline phase. The weight loss phase consisted of alternating 25% and 125% of per day of baseline energy intake for the alternate-day fasting group, and 75% of baseline energy intake for the typical restriction group. The maintenance phase consisted of alternating 50% and 150% of baseline energy/day for the alternate-day fasting group, and 100% of baseline intake for the restriction group. The control group received no specific counselling or instructions beyond attempting to maintain baseline weight.
The study group included 100 participants with a mean age of 44 years, 86% were female, and 63% were black. The alternate-day fasting group had weight loss of -6.0% (95%CI -8.5% to -3.6%), similar to -5.3% (95%CI -7.6% to -3.0%) in the calorie restriction group. There was no significant difference in weight re-gain. There was no observed difference in blood pressure, heart rate, fasting glucose, serum insulin, or triglycerides between the intervention groups, but LDL was higher in the alternative fasting group (11.5 mg/dL; 95%CI 1.9-21.1 mg/dL). The dropout rate for the fasting group was 38% vs. 29% in the restriction group and 26% in the control group.
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