Results:

A total of 100 participants (86 women and 14 men) were included. Mean age was 44 years. Drop out rates were highest in the alternate-day fasting groups (13 of 34 [38%]), compared with the daily calorie restriction groups (10 of 35 [29%]) or the control group (8 of 31 [26%]). Mean weight loss was similar for participants in the alternate-day fasting group and those in the daily calorie restriction group at the initial 6-month weight loss phase in the alternate fasting group (–6.8% [95% CI, –9.1% to –4.5%]) and in the daily calorie restriction group (–6.8% [95% CI, –9.1% to –4.6%]) as compared with the control group. Results were also similar between the two groups at 12 months. Participants in the alternate-day fasting group ate more than prescribed on fast days, and less than prescribed on feast days, while those in the daily calorie restriction group generally met their prescribed energy goals. There were no significant differences between the intervention groups in blood pressure, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein, or homocysteine concentrations at month 6 or 12. Mean high-density lipoprotein cholesterol levels at month 6 significantly increased among the participants in the alternate-day fasting group, but not at month 12, relative to those in the daily calorie restriction group. Mean low-density lipoprotein cholesterol levels were significantly elevated by month 12 among the participants in the alternate-day fasting group compared with those in the daily calorie restriction group.